Class QC S'ZJ Book_ as JsA-JLL Copyrights COPYRIGHT DEPOSIT. ACTIONS of ELECTRICITY /a. By LAND IS 1916 U. B. PUBLISHING HOUSE Dayton, Ohio .b3 Copyrighted by Electrical Education Association 1916 Arcanum, Ohio, U. S. A. APFT 10 1916 2&A427776 4^0 / , PREFACE Electricity at the present age is the most used and most convenient form of energy or power in the world. Its promises for increased use in the future for power and other utilities are beyond conception ; yet, with the foregoing facts, it is also true that a smaller per cent, of people really understand the electric current's ac- tions than almost any other science. Referring to the above conditions, it is intended by the writer that the primary principles of the most commonly used elec- trical appliances can be obtained by following the work of this book, which is not so lengthy as to become tiresome. Again, it must be remembered that the entire knowledge of electricity is beyond the space of any single book; and if it is desired to become fully familiar with all the subjects, terms, measurements, etc., numerous volumes of a standard electrical work or a special electrical course should be secured. J. A. Landis, Author. ELECTRICITY In collecting and explaining a few of the most important principles and actions of electricity used so extensively in the world, it will be the intention of the writer to explain to the reader, by the aid of the small motor, in a practical way, some of the causes, actions, and results of the electric current used to-day to run the world's factories, pull its trains, light darkness, start its automobiles, in fact, used by nearly every person in some manner. It is intended that the small motor be used in con- nection with the study of these instructions, thereby gaining the practical knowledge of what causes elec- tricity and how it is harnessed and used for results after it is caused to be. It is therefore necessary for the reader to notice the connections, wirings, etc., which can easily be removed or traced to show their positions or conditions relative to each other within the electric machine. In order to gain knowledge of electricity in an easy way and remember it, the writer knows by experience that it is necessary for practice and theory to go hand in hand, as a successful learning of our subject cannot be obtained by either one method without the other ; and it is for this reason that the small motor accom- panies this book; therefore, as each subject is handled, the reader is asked to study the make-up, shape, con- dition, and action of the machine to which it applies, so it will be fixed in his mind what each part is expected to do and does do. In plunging into our subject, first we will learn that electricity does not occupy any space, has no weight, will exist in a solid matter, in a perfect vacuum, in air, in a liquid, or in the ground ; drawing a conclusion from the above to fix a definition for it, we can only say electricity is an existing force or an existing energy in its own peculiar state of being. 5 Actions of Electricity. We will next learn that there are two principal kinds of electricity with which the world to-day has most to do; namely, static and dynamic. A static charge tends to prevent the change of motion or compel objects to come to a rest; from this, we know it is produced by friction in some various ways and under certain conditions. Friction between rain drops and air currents in the sky often produces a static charge of great enough volume that it will discharge its energy by flashing to the earth, or another position in the sky, and this discharge is known as a stroke of lightning. A small amount of static electricity can be produced and its energy noticed to expend by briskly rubbing the fur of a fur-bearing animal, and if the finger is held close to a rapidly moving belt. With the invention of the X-ray machine, the static charge was universally used. It was produced by re- volving flat disks, usually about four feet in diameter, in opposite directions ; the friction between the rapidly moving disks generated a heavy charge of static elec- tricity which was led to a special glass tube where it would expend its energy by flashing through space from one end of the wire to the other, possibly about four inches apart. This constant flash will produce rays of light so strong that they will penetrate a solid mass. Later inventions have proven the dynamic elec- tricity for the X-ray more convenient and with as good results. A dynamic charge, nearly the opposite to a static charge, tends to set objects in motion or causes them to move relatively from each other. In studying dy- namic electricity in the future, we will call it current, as it practically is known by those who handle it. As the knowledge of our subject rests largely upon two properties of the electric current, the reader is 6 Actions of Electricity. asked to strictly familiarize himself with electric measurements and magnetism as herein given, for upon these two hinge the conditions and problems of all electric work and knowledge. The electric current is measured by amperes and volts, and its flow depends upon ohms. Amperes applies to a given amount or quantity of current flowing at some certain moment. Volts denotes the pressure or the actual force which is pushing a certain current through a conductor. Ohms is that property of a conductor which tends to stop the flow of an electric current. An ohm is the unit of measure for current resistance. Figure 1. Conductors : Xon-Conductors Gold Crockery Silver Glass Copper Wood fibre Iron Slate Damp ground Dry wood Tabic No. 2 Standard Gau ge B. & S. Copper Wire Number Ohms per foot .000102 4 .00026 8 .00065 12 .00165 16 .0048 18 .0065 20 .0106 22 .0168 24 .0267 26 .0425 30 .1074 Actions of Electricity. Fig. 1. ftROWN & SHARPE WIRE GUAGR 'B. & S. W. G>) To get the idea of the amount of each term and to show their relations to each other, let us remember that one ampere is the quantity of current that, at a pressure of one volt, will flow through a conductor having a resistance of one ohm ; hence the measuring term's relation of a current actually flowing is as fol- lows : Ohms = voltage divided by amperes. Voltage = ohms times current. Amperes = voltage divided by ohms. That we may practically know the amount and value of each term by our first experiment, we will refer to the "resistance of wire" table. For instance, copper wire No. 24 has a resistance of .0267 ohms per foot ; forty feet times .0267 will have about one ohm resist- ance. If we connect both ends of this wire to a common 8 Actions of Electricity. dry-cell battery whose voltage is, usually, one volt, a current of one volt divided by one ohm, one ampere (the exact amount of current flowing in the wire). An idea of the strength of one ampere in this case can be obtained by opening the circuit and closing it with the tongue; the sensation to the tongue is caused by the flow of one ampere at a pressure of one volt. Again, if ten feet of No. 24 copper wire were used, we would have ten times .0267 ohms, or .267 ohms; one volt (the battery voltage) divided by .267 ohms equals about four amperes, which is, of course, four times the volume of the first experiment, and might be enough to burn the tongue. The zvatt is another term of current volume, and is obtained by the product of volts times amperes. Watts are generally used when speaking of the capacity of a small electric utility; for instance, a forty-watt house lamp, when on a 110-volt circuit, will consume forty watts divided by 110 volts, or nearly .3 of one ampere. Volts times amperes = watts. Watts divided by 1,000 = kilowatts. Watts divided by 746 = horsepower. Volts times amperes times hours = watt hours. Watt hours divided by 1,000= kilowatt hours. If an electric generator has a capacity of generating 400 amperes at 110 volts, it is spoken of in practice as 400 amperes times 110 volts divided by 1,000 watts, which will be about 44 kilowatts capacity. If it is desired to know how large an engine and boiler are required to drive this machine, 400 amperes times 110 volts divided by 746 watts will be about sixty horsepower. Again, if a sixty-watt house lamp burns three hours an evening for thirty evenings, it will consume sixty watts times three hours times thirty evenings — about 5,400 watt hours, which divided by 1,000 will be 5.4 9 Actions of Electricity. kilowatt hours; this times, usually, ten cents per kilo- watt hours, equals fifty-four cents, cost of light for one month. If a power motor has an average load of twenty amperes at 220 volts eight hours a day, tw r enty-six days in a month, at five cents per kilowatt hour, the cost of the current will be twenty amperes times 220 volts divided by 1,000 multiplied by eight hours times twenty-six days, which will be $45.76, cost for the month for power. The reader is asked to solve various problems made by himself with the principles of the foregoing state- ments, that he may become more familiar with the values and how to find the results of the electric measuring terms. Resistance within a conductor is, in some cases, a necessity to properly handle electricity for results. Current flowing against a resistance produces heat which is in proportion to the quantity of current flow- ing, and is not noticeable until nearly the carrying capacity of the conductor is reached, after which, if the amperes are allowed to increase, the heat within the conductor will increase in proportion until the melting point is reached. This condition is made use of in the ordinary elec- tric glass house lamp, where a small, long conductor (placed in a vacuum to prevent oxygen in air from burning it) with a high resistance and high melting point, is connected into a circuit, the flow of current through it causing its temperature to rise to a glowing red or white heat. Let us remember that if this current's voltage were raised, this would force more current through the already heated conductor and heat it to a hotter degree and probably melt it. . 10 Actions of Electricity. This condition is also practically true in electric heating and cooking, where usually iron wire in the form of a coil long enough whose own resistance at a certain voltage will allow only current enough to pass through it to heat it to almost a red heat, is used. Voltmeters, ammeters, and wattmeters properly con- nected into a circuit, will show the current's actual strength or volume. MAGNETISM Magnetism is a volume of lines of force which flow parallel in a continuous circuit; it was first discovered in a metal mined in Asia. A magnet is a magnetic conductor usually consist- ing of iron or steel, charged with a volume of lines of magnetic force which in their circuit leave the magnet and return to it again, thereby causing the magnet to have what is known as a north pole ( X), or that part /7 / i i 4 l l >' i \ i \ \ >»^ Ftg. 2, .<___ 11 / Actions of Electricity. where the lines of force leave it, and a south pole (S) where they enter again. Magnets are divided into two classes, permanent and artificial. Permanent magnets' material is usually steel, and when this material is placed in the path of a dense magnetic field or flux, it tends to charge and will per- manently retain a quantity of lines of force within itself. Nearly all magnetic conductors hold a small amount of magnetism when once charged, called resid- ual magnetism, but in practice, unless they retain a large volume of the lines of force, they are not called permanent. By noting the direction of flow of the lines of force of a magnetic circuit in the diagram, it will be seen that lines of force flowing in opposite directions can- not occupy the same space at the same time ; hence like polarity repels and poles of opposite polarity attract each other. The earth is a huge magnet ; its polarity is nearly its geographical polarity ; the lines of force flow parallel from the north pole, on the surface of the earth, and enter it at the south pole, through the earth, and out near the north pole, making a contin- uous circuit. This condition is practically used with the compass, which is a magnetically charged magnet in the form of a needle suspended to permit it to revolve freely. As the earth lines of force in the vicinity of the compass will tend to flow through the needle, its resistance being lower than the air will cause the lines of force within the compass magnet and the lines of force of the earth magnet to repel each other until they can flow within the needle in the same direction ; hence, the south pole of the compass magnet will swing on its axis to a point toward a northern direction. It must be remembered that, should the compass needle be in the vicinity of 3 magnet whose lines of force are more dense than the 12 Actions of Electricity. earth circuit, the compass needle will parallel itself with the magnetic flux most dense, because it is the stronger. Artificial magnets are caused only by the flow of electricity. If a current is forced through a conductor, there will surround the conductor in a true circle a Fig. 3. magnetic flux or lines of force; if the current in the wire is flowing from the observer, the lines of force will flow around the conductor in the same direction as the hands of a watch turn when observing it. Again, if a number of conductors are in parallel and the current is sent in the same direction through them, the lines of force that would be circular to each con- ductor will surround the entire number of conductors in its circuit; in other words, a number of conductors with a current passing through them in parallel, will Fig. 4. <::>«< have only one magnetic circuit, which is, of course, as many times stronger than one of these conductors as there are conductors. 13 Actions of Electricity. This is a condition in the electric machine ; if the field winding is examined and current traced, it is found there are a number of wires in parallel in the form of a coil ; the magnetism generated in each turn will flow around the entire coil, because the magnetic lines of force around the wire that lies next to it would repel the first wire's lines of force if they attempted to go back around it ; so the easiest path for the lines of force of all the conductors is around the entire coil, which, in the small diagram (Fig. 5) will be if the coil's end marked A is positive. The current within the coil will flow in the same direction as the SAUENT POLE FIEU> MAGNET. Fig. 5. hands of a watch. The lines of force will flow from the observer to the north pole, where they leave the magnet, and flow through the air or an armature, if there were one there, to the south pole of the mag- net, where they enter and return again field magnet. 14 through the Actions of Electricity. A magnetic field's strength is in proportion to the volume of volts and amperes and the number of turns of wire in its producing coil. If you will examine the armature of the small motor, you will find an iron ring around which is wound a coil of wire, this coil being tapped and connected to commutator bars which serve the purpose of leading the current to and from the armature winding by allowing the current to flow under each field of the magnet in the same direction at all times of a revolu- tion ; however, on all economical machines, a greater number of coils are tapped to commutator bars, thereby making that machine more efficient. Fig. G. Fig 7 If a current is sent through the magnet field coils, lines of force will flow from the north pole to the armature ring and from the armature ring to the south pole. If a current is sent through the coils on the arma- 15 Actions of Electricity. ture ring at that same time, lines of force are set up from each turn and repel those of the field, as shown in Fig. 7; they cause the field lines to crowd away, as two different sets of lines of force cannot occupy the same space or flow in the same direction at the same time. This action in turn causes the flux of lines around the conductor to crowd away from the true center to their conductor; the torque, or pulling effect, of these lines on the conductor to bring it to their true center, will cause the armature to move forward. By referring back to Fig. 6 and to the motor, and applying above condition, we can easily see that, while the conductors under the north pole must travel in an opposite direction to those under the south pole, the current in the armature coils between the armature ring and the field's north pole and the armature ring and the field's south pole also flows in an opposite direction, making a constant pull on the armature in the same direction. The direction of rotation of a motor armature can be ascertained if the direction of flow of current in the armature and the direction of flow of magnetism in the field is traced. By referring to Fig. 6, the lines of force in the field are flowing from the north pole, and the current in the armature coils between that pole and the armature ring is flowing from us observing it ; hence, the field lines of force will crowd those lines around the armature conductors to the right and tend to push the armature in the direction that the arrow points. By the above, we can readily see that, to change the direction of flow of current in both the armature coils and the field coils will not reverse the direction of the rotation of the motor, but to change the direction of flow of current in either the field or armature and let 16 Actions of Electricity. the other remain will change the direction of rotation of the armature. There are various types and connections of direct- current machines, shunt or multiple, series and com- pound wound fields, and multiple and series wound armatures. 6666660 Q I OO? Lamps^ Lir I ■Multiple Figure 8. — compound wound dynamo. Fig. 8 shows clearly the connections of a compound wound generator. The current produced in the arma- ture leaves at A and flows to the lamps through the line returning from the lamps flowing through the series field winding and back to the armature. The shunt field is connected to the positive lead, the current flows around the multiple field winding through a rheostat, which is only an adjustable resistance and connects to the negative lead of the machine. It has been shown by the action of the electric cur- rent in the motor that magnetism is the means of ob- taining power by expending the electric current's en- 17 Actions of Electricity. efgy, and it has been mentioned before that dynamic electricity is obtained from magnetism. If a conductor with a closed circuit is moved across a space in which there are flowing lines of magnetic force at right angles to it, the conductor will tend to cut these lines of force, which action will send a charge of electricity through the conductor. Fig. 9. A.M. By referring to Fig. 9, the long arrows represent a field of lines of force flowing from the north pole to the south pole. A wire conductor is cast into this field at right angles to the lines of force and is con- nected to two commutator bars ; these bars are con- nected to two brushes, marked B Positive and B Nega- tive, and these brushes are connected to a closed cir- cuit through an ampere meter. It can readily be seen that, with the wire turned a part of a revolution near its shown position, it will 18 Actions of Electricity. move nearly in the same direction as the field magnet- ism is flowing; but if the wire is turned one-fourth of a revolution it will be cutting lines of force at the fastest possible right-angle rate, and a current of elec- tricity will be shown flowing through the ampere meter. After the conductor has passed one-half of a -revolution it will begin cutting lines of force in the opposite direc- tion; therefore, the direction of flow of current in the wire will be reversed; but after one-half of a rev- olution the commutator segments will also have changed brushes and the current will flow in the same direction as before through the meter. A conductor cutting lines of force will carry off a current in only a certain direction; for instance, if a wire cutting lines of force under a north pole is moved from left to right, the direction of flow in the wire will be away from the observer. A short rule for finding this condition is given by placing the middle and forefinger and thumb of the right hand at right angles to each other, and the result will be obtained as shown in Fig. 10. Fig. 10. After studying the principles and actions of the motor and generator, we may wonder why a motor pulling no load will not continue to increase in speed. 19 Actions of Electricity. It is the action of a generator within the motor that acts as its speed governor ; for instance, if the direction of current within a motor is ascertained, and under these same connections and rotation of the armature if run as a generator, it will tend to generate a cur- rent in the opposite direction to that as supplied when run as a motor. This is the condition within the motor; for, if a current of, say, 220 volts is supplied, the motor will increase in speed until it will he running fast enough to generate a voltage (nearly 220 volts) whose current tends to flow in the opposite direction to that of the motors, and this counter current will stop or act as a resistance to the supply current ; if a load should come on the motor, its speed will drop, which action in turn will lower the counter voltage and allow more supply current to flow. By noting the above, it can be understood that the counter current generated within the motor will allow T the supply current to flow only in proportion as the load is on the motor. Within a generator, pushing a current through a cir- cuit, it acts as a motor tending to run in the opposite direction from that which it is driven, which action is due to the current that is generated flowing through the armature conductors and in so doing sets up a magnetic flux around each conductor as in the case of a motor. If this condition is studied, it will be found that the generator is driven in an opposite direc- tion from that it would run if run as a motor ; from this condition, it can be seen that the more current gen- erated, the more power will be required to drive the machine. There are various types of armature shapes and con- nections, the main object of all armature windings being to get the longest amount of wire under the fields with a minimum amount for connections and turns. 20 Actions of Electricity. The small motor has a ring winding and is multiple wound ; for if we can imagine this style armature wind- ing under, say, two pole sets (four poles), it would be necessary to have four brushes connected to the commutator or one under each pole piece to distribute and collect the current equally. Drum-wound armatures are found by wrapping the coils around the entire armature in the same way as wrapping string around a ball. The style of winding used in most electric machines at the present time is a ring lap (multiple) or a wave (series) winding, and is generally used on machines having more than one set of poles. As seen by referring to Fig. 11, the armature is Cross Sect/en of S/ot m ' Coifs ; Co// Leads 7erm/rra/j. Com. Bars . Actions of Electricity. slotted and the conductor coils are laid in the slots in groups; a multiple-wound armature coil can be traced by starting at commutator bar a (Fig. 11), through slot No. 1 under, say, a north pole, then horizontal with the ring of the armature and back in a slot under the south pole, connecting to a bar next to the one started from, and so on around the entire armature. By referring to the small motor, we can see that the brushes are connected to the commutator segments which connect to the armature winding half way be- tween the poles, thereby utilizing all the coils under each pole. A series winding, unlike a multiple winding, does not return from its coil to a commutator bar next to where it started, but leads ahead as shown in Fig. 12; this type of connecting, it will be seen, throws the entire winding. in series; therefore it requires only one posi- Fig. 12. Actions of Electricity. tive and one negative brush connected to the bars lead- ing to the coil in the slots half way between either set of poles. By referring to Fig. 13, we will see that the rotation of the armature draws the field's lines of force ahead Fig. 13. or moves the field magnetic flux ahead from the true position of the pole pieces ; this actual condition in any machine is overcome by shifting the brushes on the commutator back or forward until they do not spark, which position when found will be the true magnetic field. ALTERNATING CURRENT An alternating current is a quantity of electricity which flows in one direction, then reverses and flows in the opposite direction, these reversed directions of flow occurring at the rate of from 1,000 to 10,000 per 23 Actions of Electricity. (VI Alternator Fig. 14. minute ; the current which flows back and forth is in practice divided as shown in Fig. 15, which is the time of the coil to pass the distance of one set of field poles making one complete cycle or two alternations. Alternation^ \ v i - ^ % ; Fig. 15. 24 Actions of Electricity. From this fact, we can figure that the machine in Fig. 14 will produce a current of four cycles per revo- lution of the armature. As previously explained, the current in the armature coils is generated and flows in one direction while pass- ing under a north pole, and reverses and flows in the opposite direction under the south pole; this is the actual condition of an alternating-current electric ma- chine, the winding of which is shown in Fig. 14, where the coils under all the poles are connected in series, the ends of which connect to two rings and the current is led from the rings by brushes flowing as generated, first in one direction when one half of the coils is under a north pole and the other half under the south pole, and completely reverses and flows in the opposite di- rection when the armature revolves the distance of one pole, thereby bringing that half of the armature coil that was under the north pole now under the south pole. The effect of the magnetism in both direct- and alter- nating-current machines is about the same, but there is some difference in their conditions; an alternating current generator must have its field circuit supplied with a direct current from a direct current generator or some other outside source, so the magnetic lines of force in their circuit will flow in the same direction. It is practical in most cases to charge the field of an alternating current motor or the series field of a gen- erator with a rectified alternating current ; a rectified or pulsating current is unlike an alternating current in 25 Actions of Electricity. Fig. 16. that each alternation per cycle flows in the same di- rection instead of reversing its flow. This condition can be obtained by placing on the shaft of the motor (or generator for a series field winding only) a com- mutator with as many bars as there are field poles on the machine, as shown in Fig. 16, where // represents the armature coils, B the commutator on the shaft of the machine, and S the leads connecting each bar to the second bar. From it, these two sets of bars being connected in series with the armature coils and with two brushes on the commutator the distance of one, three, five, etc., bars apart, will be produced in the 26 Actions of Electricity. series field C a direct pulsating current, the shunt field winding F being excited by a direct current generator. An alternating-current motor cannot be started by its own power and brought to speed like a direct-cur- rent motor, for the reason that the current applied to the motor reverses continually in the motor's armature coils and the forward pull by the first alternation is so quick that the armature cannot get started until the second alternation would tend to pull it in the opposite direction. For this reason, it is necessary, when start- ing an alternating-current motor, to bring it to a speed by some outside power that it will have the same "fre- quency" (number of complete cycles per minute) as its supply current, and that its alternations start at the same time and in the same direction as that of its supply current. It may then be connected with the supply cur- rent, as it will be running fast enough to generate a counter current which will prevent a rush of current through the armature coils. The phase difference be- tween any two machines can be found by connecting a bank of lights straight in series with the two circuits ; if they are in phase, the lamps will not burn, because there is no voltage or phase difference between the two circuits; if they are entirely out of phase, the lamps will burn brilliantly, for the voltage difference between the two machines will be double the voltage of one machine. As an alternating-current motor runs in phase or step with its supply current generator, it will be readily seen that the motor wall not gain or lose in speed only as its generator gains or loses in speed; and if a load should come on the motor, it will not drop in speed, but its generated counter current will lag behind the supply current which allows more supplied current to flow ; the above-mentioned lag is small, but in propor- tion to the motor's load. If a load should come on the 27 Actions of Electricity. motor so heavy as to reduce its speed the distance of one pole piece on the armature or one alternation, the motor will buck the current of its generator and stop, as its counter generated alternations will then be in an opposite direction to those of its generator. Two-phase alternating-current machines are built with two separate sets of windings and four collecting rings and are in reality two single-phase machines built in one. Three-phase machines, the most generally used alter- nating current generator, shown in Fig. 17, has on its armature three separate windings, each winding being one-third of the distance on the armature as the space covered by one set of field poles ; the three separate armature windings are connected together at one end 28 Actions of Electricity. and the other end of each is connected to a collecting ring. If the current in Fig. 17 is traced, we will find that three separate single phases are generated or one between each of the three collecting rings; by using this method of placing the three separate sets of coils at equal distances apart on the armature, it will at once be seen that the current will be more equally distrib- uted around the armature. It will be possible to get three separate phases from only three wires, thereby favoring the distribution of the current to various dis- tances and places. TRANSFORMERS By referring to Fig. 18, we will see that a trans- former consists of an iron core C around which is c I A , A ■P 1 I Ratio, » m H i ■ 3 ) r-l > p \ to ' '< 1 • .*s o ► o to p-i to ; I rH V Fig 18. wound a primary coil marked P which is supplied with ingle-phase current, a second or secondary coil 29 Actions of Electricity. marked ^ which generates a current nearly equal in quantity to that in the primary coil. If an alternating current is sent through the primary coil, a magnetic circuit will be produced around the iron core, its strength being in proportion to the strength of the current and the length of the coil. As this magnetic circuit is constantly reversing, it will have a volume ranging from zero to a maximum, and the coil in the secondary winding cutting all the lines of the produced magnetic circuit (acting the same as the coils on the armature of a generator except the lines of force move and in the generator the coils move) will generate a current equal in quantity to that of the primary. As the number of lines of force generated within the core depends upon the length and the voltage of the primary coil, so does the generated voltage of the sec- ondary depend upon its length and number of turns for cutting lines of force to produce a certain voltage. By referring to Fig. 18, if the voltage of the primary current is 330 volts and 10 amperes of current are flowing, the ratio of transformation being 3 to 1, a current of 30 amperes at 110 volts pressure will be generated in the secondary coil, or a current of the same value with a different voltage and amperage as that in the primary coil. As the current in the primary coil produces a mag- netic circuit in the transformer's iron core, the induced magnetic lines of force will tend to generate a counter current in the coil, whose voltage is nearly as high as that supplied, and it is this condition of reaction that allows only a very small amount of supply current (known in practice as transformer loss) to flow when the secondary coil is open. If under this condition a load should come on to the secondary coil, it will at once begin cutting the lines of force in the core pro- 30 Actions of Electricity. duced by the current in the primary coil, and a current will flow which will tend to set up a magnetic flux in the core in an opposite direction from that of the counter generated current in the primary, which condi- tion will reduce the pressure of the primary coil's coun- ter current, thereby allowing more current to flow in the primary coil, or a volume in proportion to that used in the secondary coil. The transformer may be used to step a voltage up by using the coil with the least number of turns as the primary coil. Let us refer to Fig. 18; if a tap (wire) were con- nected to the secondary coil in its middle, the voltage produced between this tap and either end of the coil will be only one-half the voltage of the whole coil's voltage; this condition is practical where it is desired to run a power line for a motor of, say, 220 volts the voltage of the entire secondary coil and a line be- tween the tap and either end of the coil for a lighting circuit of 110 volts. 31 Actions of Electricity. INDUCTION MOTOR The principle of an induction motor is much different from that of the direct-current machine, and is similar to that of a transformer. It is made up of a "stator," "rotor," and "rotor supports" or bearings. The stator, as shown in Fig. 19, is a field frame with, we will say, three single-phase windings equally dis- tributed on its inner surface in the same position rel- ative to each other as on a three-phase alternater. Fig. 19. (a) (b) The rotor is simply a magnetic conductor with a number of heavy bars of copper across its outer sur- 32 Actions of Electricity. face, the bars all being connected at their ends by a copper ring. If a three-phase current is sent through the stator windings, the magnetic circuit produced will whirl iorward around the inside of the stator with the same principle as that if the field frame of a direct-current machine rotated ; with this condition in the stator, the heavy copper bars on the rotor cutting the whirling lines of force will produce in them a heavy current which will produce around the copper bars a flux of magnetism, which flux will be opposed, and a pulling effect upon the rotor caused by the whirling magnetism until the rotor's speed reaches that of the whirling magnetism, when no lines of magnetism will be cut and no current generated in the bars on the rotor. At this speed, if a load should come on the motor, its speed will lessen enough that the heavy copper bars will start cutting more of the whirling field's line of force, which action acting the same as the primary coil of a transformer will allow more current to flow through the stator coils, whose magnetism will also increase and cause a greater torque on the rotor, as it will cut the increased magnetism thereby regulating the speed. When a single-phase circuit only is available for the induction motor, it is usually built with a split phase, or two phase in multiple, one being placed about one- fourth its own distance ahead of the other whose resis- tance is about one-fourth that of the other, thereby causing one phase to lag producing the action of a two-phase current. With this arrangement, the motor will have a small starting torque, but after attaining its phase speed will act practically the same as if its stator were supplied with a double or three-phase wind- ing. 33 Actions of Electricity. ROTARY CONVERTER To the present time, by using the rotary converter or transformer is the most successful method of changing alternating current to direct current or direct to alter- nating current, and, as is seen in Fig. 20, the rotary converter is a simple direct-current machine and a simple alternating-current machine all connected to- gether from one winding; if a three-phase current is led into the machine through its rings and run as a motor, a direct current can be taken from the com- mutator; if the machine is run as a motor by a direct current, an alternating current can be taken from its rings. The value of the current in watts is the same 34 Actions of Electricity. during any transformation through a rotary, but the change of voltage in transforming a current either way is : single phase, direct current 100 volts, alternating current 71 volts; three phase, direct current 100 volts, alternating current 61 volts. STREET- AXD IXTERURBAN-CAR CONTROL The motors of an electric railroad car are in nearly all cases supplied from a 600-volt circuit, the motor's armature is usually wound with a series thereby allowing a wide range of pulling speed. By referring to Fig. 21, the most used system of current control shows the handle of the controller con- nected to the trolley or positive side of the circuit; if winding, Fig. 21. the handle is moved to the first point, a position making contact with the resistance marked R, the current will flow from the trolley through the handle of the controll- er, through the entire resistance, through the motors M, and to the ground or negative wire, returning to its generator, thereby making its circuit. As will be seen, 35 Actions of Electricity. with the controller handle on the first point, the motors are connected in series; thereby the voltage on each machine is only about 300 volts, and the resistance marked R and the resistance within both machines, all in series, allow only enough amperage to flow through the motors to start the car without a sudden jerk. After the car has started to move, the controller handle can be moved to the second point, and a little later to the third point, where the conditions are the same as on the first point, except that less resistance is in the circuit; the fourth point has no resistance in its cir- cuit, and by the time this point is reached the motors are running fast enough to generate a counter voltage which will act as a resistance and allow only enough current to flow through the motors to keep the speed of the car normal at half speed. The next or fifth point of the controller connects the motors so the current flows through all the resis- tance and through the motors connected in multiple, thereby increasing the voltage of each machine which in turn increases its speed. The condition of the sixth point is the same as that of the fifth, except less resistance is in the circuit ; the seventh point connects the motors in multiple across the line without any resistance in its circuit, and is the full-speed running point of the car. There are different makes of current control, some having eleven, some thirteen, and some more points on the controller; some makers place a shunt across the motor field circuit to weaken the field's magnetism on the last point, which condition will lessen the generated counter voltage of the motor thereby increasing its speed. Some interurban electric railroads are operated upon a 1,200-volt circuit, and in this case the system of control is practically the same as shown in Fig. 21 36 Actions of Electricity. except that all four motors are connected in series on the first or low-speed points, and on the last or high- speed points they are connected in two pairs, each pair being in series, the two pairs in multiple. ELECTRO-PLATIXG— ELECTROLYSIS Let us drive into the damp earth one copper bar and one iron bar and connect a direct current of electricity to the exposed ends of the bars so the current will flow from the copper bar to the iron bar through the damp earth ; this action of the current leaving the copper bar will decompose it and make a deposit of copper on the iron bar where the current enters it ; this action is called electrolysis and is used practically only for electro- plating. By referring to Fig 22, a cleansed spoon and FlG. 22. r Electro- plating. coin are placed in a non-acid, current-carrying solution (usually cyanides of silver and potassium) and con- nected to the negative side of a battery or low voltage generator. The positive current from the generator or battery is connected to a plate (gold, silver, copper) 37 Actions of Electricity. metal which is desired to be plated on the spoon or coin and that metal laid in the solution close to the spoon and coin ; the current flowing from the metal terminal in the solution to the spoon and coin will tend to carry particles of the metal and deposit them uni- formly in a solid mass on the surface of the spoon and coin. The thickness of the plate caused by the above operation will depend upon the strength of the current and the time allowed to flow. STORAGE BATTERY Years ago, some scientist discovered that if two metal plates were immersed in a solution of acid and a cur- rent of electricity sent through the acid from one plate to the other, a chemical action of the acid and plates would take place. If that current were removed and a wire connected to the two plates, a current of elec- tricity flowed in an opposite direction, which was pro- duced by a further or rather reversed chemical action in the acid and plates. The extensively used small or large storage battery of to-day does not vary in principle from the above. The experimenters have found that one of the most efficient batteries is made up of a sulphuric-acid solu- tion ; the plates are usually a lead grid framework and made solid by covering the grid with oxide of lead, which is the best material known to produce the re- quired chemical action between itself and the acid when the battery is being charged or discharged. The lead grids or plates are placed side by side in the sulphuric-acid solution and are kept from touching each other by placing between them glass tubes or per- forated hard-rubber plates. There may be as many plates as desired in a single cell ; usually the end plate and each third, fifth, seventh, etc., plates from it are 38 Actions of Electricity. |typicai, storage battery. Fig. 23, connected together, and form the negative, while the second, fourth, sixth, etc., plates from the end are connected together and are made the positive. After a battery is once charged, it will produce a current in voltage and volume as great as that con- sumed in charging, and acts only as a storage for electrical energy by the process of a chemical action and reaction; any single cell, regardless of its size, will produce only about two volts, but from one to one and one-half amperes per square foot of plate surface area. AUTOMOBILE ELECTRIC EQUIPMENT The electric equipment of an automobile usually 39 Actions of Electricity. consists of a battery, ignition system, generator, motor, lamps, wiring, switches, etc. The ignition system's current is of very low amper- age and high voltage, and is produced either by a mag- neto or current from a battery run through a voltage step-up coil or transformer; the voltage of the current must be high enough that it will jump through space nearly one-fourth of an inch, so when the circuit is closed to the spark plug it will jump the gap of the plug's contacts, thereby making an arc or a spark and exploding the gas. The current is led from its source to a distributer (which is a mechanical appliance connected with the engine shaft) that closes the circuit at the same instant during that part of a cycle or revolution that a charge of gas is correctly ignited in the cylinder. The lower half of Fig. 24 shows the connections for an electric lighting and engine-cranking system used only on the smaller size engines, as can be seen by Fig. 24. IxslSiSlZSi&iJ 40 Actions of Electricity. noticing the cut. The generator-motor, GM (in this system combined in one unit) is connected by wire on one side through a relay and starting switch R to one side of the battery B and through the lamp control switches to the various lamps L ; the other side of the generator, battery, lamps, etc., are connected to a common ground or the frame of the auto which com- pletes the path of the current's circuit. If it is desired to light the lamps, their control switch is closed and the current will flow from the battery through the frame of the auto, through the lamps, returning to the battery through the wire and control switches. If it is desired to start the motor and crank the engine, a lever attached to the relay and starting switch is pushed or pulled by the operator that closes the switch between the battery and motor, and the current will flow from the battery through the motor turning it as desired; the starting lever is then released and the starting switch opens automatically; this action will draw electrical energy from the battery which is re- placed by charging the battery in the following manner : After the engine is once running at a speed of about ten miles per hour on high, the motor-generator be- comes a generator whose voltage at this speed is about the same or a little higher than the battery voltage, and is high enough to produce enough magnetism in the re- lay coil to close the starting switch, thereby throwing. the battery with the generator ; as the engine speeds the generator faster than the above speed, called the "cut in" and "cut out" speed, its voltage will tend to rise, which action will force more amperes through the bat- tery. Let us refer to the upper cut of Fig. 24. As the generated ampere load increases, the action of the multiple field with one terminal connected to a third brush on the commutator midway the main brushes, causes the true field magnetism to distort and weaken 41 Actions of Electricity. in proportion to the ampere increase, until the gener- ator will produce seldom more than ten or twelve am- peres regardless of how fast the engine is run. When the speed of the engine is stopped, or lowered to a speed that the generator voltage falls to or a little below the battery voltage, the current would tend to flow back through the generator, making it a motor, which condition will cause the relay to open the start- ing switch and separate the battery and generator. Fig. 25 shows a complete system of wiring of the larger size automobile engine and consists of a storage battery, starting motor, and generator as separate units, current regulator, switches, lights, wiring, etc. Before trying to trace the current of this system, it will be noticed that one side of the current has a ground flow, or the one side of each apparatus (lights, motor, generator, ignition, and battery) is connected to the frame of the machine, and the other side of each appa- ratus is connected by wire through its control switch to the battery, completing the circuit. If it is desired to start the engine, the control switch is closed by the operator and the current will flow from the battery through the frame of the machine to 42 Actions of Electricity. Tl t j j i the motor (which is a simple, direct-current motor con- nected by a gear or chain to the engine shaft), through the control switch, back to the battery, making its cir- cuit. 43 Actions of Electricity. The ignition system and lights are controlled prac- tically the same as above, each having in its circuit a switch which, when closed, allows the current to dow from the battery, through the frame of the ma- chine, through the lights, etc., back to the battery. The control of the generator is left entirely to the regulator which acts automatically to perform its duty ; the generator is geared to the engine shaft and is mul- tiple field wound. Let us refer to the action of the regulator, the normal condition of which is shown that the "regulating spring'' holds the "regulator contacts" closed, thereby closing the multiple field circuit of the generator; the "cut out" and "cut in" contacts which connect the generator with the battery, are normally open until the speed of the engine is running the auto at a speed of about eight to ten miles per hour, at which speed the generator will be running fast enough to generate a voltage as high or a little higher than the normal battery voltage and will be forcing enough cur- rent through the multiple field circuit which has in series with it a shunt coil, which coil will produce a magnetic flux strong enough to pull the "cut in arma- ture" toward it, thereby closing the contact points and throwing the generator and battery together. The condition of the regulator will remain the same as above so long as the generator does not vary in speed; should the generator lower in speed, its voftage will also lower to an amount that no current will flow through the series coil and not enough through the shunt coil in series with the multiple field winding to hold the cut-out armature, and its spring will pull the cut-out contacts apart, separating the battery and gen- erator. Again, after the battery and generator are thrown together and the generator increases in speed from its "cut in" speed, the current and voltage w r ill tend to 44 Actions of Electricity. increase also, but as a "series compensating" coil is in series with the armature circuit, which when cur- rent is flowing in it large enough not to be injurious to the battery a magnetic flux will be generated in it that will pull the "regulating armature" toward it, thereby opening the multiple field circuit; but a part of the current will continue to flow through the "regulating resistance" which does not permit the magnetic field to be destroyed but weakens it, thereby lowering the volt- age and amperes of the armature, which action will reduce the magnetic pull of the "series compensating" coil and let the regulating armature release and close the "regulating contacts." This action is continuous and the faster the speed of the generator the quicker the contact points will open after closing, thereby keep- ing the voltage and amperes to a minimum regardless of the speed of the generator. Later improvements on this system have connected in the battery circuit a relay coil which automatically opens the battery circuit when the battery voltage is a maximum at which point the battery is fully charged, thereby saving the battery from being constantly charged on long runs. 45 Actions of Electricity. ELECTRIC ARC LAMPS When an electric current flows through space, it tends to heat both conductors between which it is flow- ing, and is the condition within an arc lamp. By referring to Fig. 36, w r e will note two carbon conduc- tors that are automatically held separated while a cur- rent of usually about fifty volts and six amperes is flowing through the lamp and across the space between — co«-J„ the separated carbons. The action of the current leav- ing the positive carbon and flowing to the negative carbon with the above-mentioned current will cause the ends of the carbons to become heated to nearly 9,000° Fahr., at which heat they will be brilliant white 46 Actions of Electricity. and produce a light of possibly 1,500 candle power. The action of the current flowing across the gap in the carbons tends to decompose the positive carbon and carry its particles in the same direction as its flow, which condition will cause the positive carbon's end to form in the shape of a crater and the negative carbon's end pointed. While no current is flowing in the lamp, the positive carbon drops and makes contact with the lower carbon ; when a current is started through the lamp, the posi- tive carbon is instantly separated from the lower car- bon by the action of the series coil's magnetism pulling the iron core or solenoid toward it, thereby raising the washer clutch which catches the carbon and raises it also. The fact that the wider the arc "gap" between the two carbons the higher will be the resistance, and as the magnetic pull of the shunt coil on the solenoid is constant, and in an opposite direction from that of the series coil, the solenoid will be held in a balanced posi- tion at which the carbon arc gap will be about one- fourth of an inch and just enough to allow a current of six amperes to flow. Where arc lights are con- nected in series, as in street lighting, and the light ceases to burn while the current is still flowing (which is caused by a carbon sticking or burning out), the current is permitted to flow through the lamp by the action of a relay that by-passes the current across the arc gap. ELECTRICAL TROUBLES There are various kinds of trouble that occur occa- sionally to any electrical apparatus. It has been heard said in the practical operation that electrical units seem- ingly never show the same effect when in trouble ; hence it can at once be seen how important it is to 47 . Actions of Electricity. know the current's primary actions and principles when trying to locate an improper condition within an elec- trical apparatus. Various kinds of trouble may occur and we will take up the two most usual, namely, "short circuits" and "open circuits. " A "ground" or short circuit may be caused by a punctured insulation on some current- carrying lead, which condition will allow the current to flow through a conductor, thereby leading it away from its proper course of flow through the apparatus. This condition will usually require a heavy supply of current or power, and can sometimes be located by the extra heat produced at the place where shorted by the flow of a volume of current ; however, if there is no heat produced, a test will be required to find the wrong path of the current. Open circuits are very common and is a condition where a current is stopped from flow by contacts or connections being separated (by vibration or other cause) ; a lead in the circuit may have become heated and melted, thereby separating, or a break in any con- ductor where its ends are apart will prohibit the current from flowing : in nearly all cases of trouble, if the open contact is not where it can be seen, it will be necessary to make a test to locate the open in the cir- cuit. REVIEW QUESTIONS The following questions are very simple and can be answered if the contents of this book are first familiar- ized. The reader is asked to make answers in his own language and draw diagrams of his own made- up style so far as possible without referring to the book, and afterward compare, so an impression will be made upon the mind and the subject will be more easily remembered. 48 Actions of Electricity. 1. What is electricity? 2. Name at least two kinds of electricity. 3. What kind of electricity causes lightning? 4. How is static electricity produced? 5. Name two important properties of dynamic electricity. 6. Name four units of measure of an electric current. 7. Write the name of some conductors ; non-con- ductors. 8. How many amperes at ten volts pressure will flow through a conductor having a resistance of five ohms? 9. What will be the cost of burning ten forty-watt lamps eighty hours at ten cents per kilowatt? 10. Explain how an incandescent lamp produces light from electricity. 11. What is magnetism? 12. Why will a compass needle point toward the north ? 13. Explain how a magnetic circuit is produced. 14. Explain the actions of magnetic lines of force in detail by a drawing of a direct-current motor. 15. Make a drawing showing three motors con- nected in series on one line and three motors connected in multiple on the same line. If the voltage across the terminals of one of the motors in series is 110 volts, what will be the voltage across the terminal of one of the motors connected in multiple? Why? 16. Explain fully by a drawing how dynamic elec- tricity is produced. 17. How is the speed of a motor controlled? 18. Explain why a generator requires increased driving power as its output load increases. 19. Make diagrams showing the different styles of armature and field winding. 49 Actions of Electricity. 20. What is an alternating current? a pulsating current ? 21. What is the frequency of an alternating current generator having thirty field poles and running 120 revolutions per minute? 22. Why will. an alternating current motor not start itself ? 23. What is a transformer? 24. The primary coil of a transformer has flowing in it a current of 1,000 amperes at 500 volts; at what voltage and how many amperes w 7 ill flow in the sec- ondary coil if the ratio of transformation is 1 to 10? 25. Explain in full the action of an induction motor's magnetism. 26. Explain how to change an alternating current to a direct current. 27. How is the current controlled within an elec- tric street or interurban car? 28. Explain the method of plating with electricity. 29. Explain the action of an electric battery. 30. What is a solenoid ? 31. Describe the action of an automobile electric battery system. 32. Make a drawing of the control of an automo- bile battery system and explain from it the action of its control in detail. 33. What is the temperature of an arc lamp's arc? 34. Explain the action of an arc lamp from a draw- ing. 35. If a motor would not start when a current is applied, what would you do? 50