Part 3

=Magnetic Blow-Out.= On the Type K controller as well as on most other successful controllers, the flashing or arcing between contact rings and fingers, which occurs when the circuit is broken, is materially reduced by a magnet that produces what is called the magnetic blow-out to extinguish the arc. This magnet derives its current from the main circuit, and is so arranged as to create a strong magnetic field in the neighborhood of the place where the arc is formed. Fig. 21 shows a Type K controller open with the magnetic blow-out magnet thrown back on a hinge. The coil which produces this magnet is seen in the right side of the controller. The main contact drum is in the middle, and the reversing drum at the right hand. There are in use a number of other controllers built upon these same general principles but differing in mechanical arrangement.

=Controller Notches.= All controllers are provided with some device which prevents the motorman from stopping the controller handle between the various points or notches, as the stopping between points might result in drawing an arc or an imperfect contact. The most common arrangement to prevent this is a notched wheel on the controller shaft, against which bears a small wheel of just the right size to enter the notches. The small wheel is held against the notched wheel by a strong spring. As the tendency of the small wheel is to seek the bottom of the notches, it is difficult to stop the controller handle anywhere between notches, and the motorman is thus given a guide which tells him without any effort on his part just where the notches are.

To prevent advancing the controller handle too rapidly and avoid the jerking of passengers, excessive currents and slipping of wheels during acceleration, several devices have been planned. On the multiple unit control systems, a limit switch is usually provided which prevents the controller advancing when the current exceeds a predetermined amount. A device to accomplish the same results on the K type of controllers is termed the Automotoneer. A cam connected with a dash pot prevents movement of the controller handle to the successive notches faster than a previously prescribed rate.

A switch is usually provided in a controller, for cutting out of service one motor or a pair of motors if defective, and allowing the car to proceed with the good motor or motors.

[Illustration: Fig. 28a. Car Wiring for G. E. Train Control System.]

[Illustration: WESTINGHOUSE 300 K.W. DIRECT CURRENT ENGINE TYPE THREE-WIRE GENERATORS.

Pittsburgh, Cincinnati, Chicago and St. Louis Railroad, Columbus, Ohio.]

MULTIPLE-UNIT CONTROL.

A system called “multiple-unit control” or “train control” has come into use where it is desired to operate motors under a number of different cars in a train; all the motors being controlled from the head of the train or from any other point on the train where the motorman may be stationed.

There are several types of multiple-unit control. In all of them there is on each car a controller of some kind which controls the current flowing to the motors on that car. This controller is operated from a distance by means of electro-magnetic or electro-pneumatic devices controlled by circuits called _pilot circuits_, which circuits are connected to the motorman’s controller. All the pilot circuits of a train are connected together by means of train plugs which make the connections between the cars. The pilot circuits of each car are connected to a motorman’s controller on that car and this makes it possible to operate the train from any controller.

=Sprague Multiple-Unit System.= In the earliest form of multiple-unit control—which was that devised by F. J. Sprague—the motors on each car were controlled by an ordinary Type K controller, which had geared to its shaft a small pilot motor. The pilot motor was controlled by the pilot circuits connected with the motorman’s controller.

In the more recent forms of multiple-unit control, the use of main controllers having contact cylinders has been practically abandoned. The contacts are made instead by a number of electro-magnetic or electro-pneumatic contact devices sometimes called _contactors_.

=General Electric Train Control.= In the General Electric train-control system each contact for the motor circuits is made by a solenoid magnet which draws together two heavy copper contact fingers to establish the circuit. A magnetic blow-out coil in series with the contact is also provided. The contactors make contact only when energized by a small amount of current from the master or motorman’s controller. In Fig. 28_a_ is a diagram of the car wiring for a motor car equipped with this system. The motorman’s controller is a drum controller, but is comparatively small since it has to handle only the small amount of current necessary to operate the solenoid magnets of the contactors. It is evident that by connecting together the pilot circuits, which are connected to the motorman’s controller, so that the pilot circuits will be continuous for the entire length of the train, any number of cars equipped with the train-control system can be operated; and similar contacts will be made by the contactors under all the cars simultaneously, by virtue of the circuits established by the master controller at any platform.

Besides controlling the contactors, the master or motorman’s controller must control an electro-magnetic reversing switch, or _reverser_, to change the direction of car travel.

The handle of the motorman’s controller is provided with a push button, which must be depressed while the current is turned on. Should the motorman release this push, the circuit through the controller will be opened and all the contactors will fall open. This handle is called the _dead man’s handle_ because it is put there to provide for cutting off the current should the motorman fall dead or in a faint at his post.

The flow of the current in the control circuits, which operates the reverser and picks up the contactors on the several points may be followed in the diagram Fig. 28_a_. With the reverse handle in the forward position and the controller on the first point, current passes from the main circuit through a single-pole fused switch called the control switch and through the auxiliary blow-out coil to a finger bearing on the upper section of the master controller cylinder by which connection is established to the adjacent finger and thence to the reverse cylinder. It leaves this over wire No. 8, passing by way of the connection board and control cut-out switch to the forward operating coil of the reverser, thence through the forward blow-out coil and over wire 81, through the switch underneath contactor No. 2 and to ground G, by way of wire B 2 after passing through the fuse shown. The current through the operating coil of the reverser, having thrown this, the path is changed somewhat. The current then instead of passing from the reverser over wire 81, is conducted through wire 15, through the operating coils of contactors No. 1, 2, 3, and 11 in series, through the switch under contactor No. 12, and to ground through finger 1 of the controller. Contactors 1 and 2 are in multiple and when raised connect the trolley with the contactors controlling the resistance leads. Contactor 3 connects R to the line while contactor 11 places the two motors in series. The motors then operate with all of the resistance in circuit. When contactor 2 raises, it opens the switch immediately below it, making it impossible for the reverse to operate while current is flowing through the motors. On the second notch of the controller an additional path is opened by way of finger 3 of the controller. This path leads from finger 3 through four of the control circuit rheostat coils, through contactor No. 5 and to ground over 32. On the 3rd, 4th and 5th points contactors 6, 7 and 9 respectively are raised. The motors are then in full series. Between the 5th and 6th points all the control circuits are broken preparatory to starting the multiple connections of motors. On the 6th or the first multiple point the ground through finger 1 of the master controller is opened while a ground through finger 3 is established. The current from the reverser then, after raising contactors 1 and 2 as before, instead of passing through contactors 3 and 11, passes through the coils of 4, 12 and 13, through the switch under contactor 11 and to ground over finger 2. Contactor 12 connects motor No. 2 to R₇, while contactor 13 grounds No. 1 motor. The motors now operate in parallel and on successive notches of the controller, contactors 6, 7, 8, and 9 are raised, cutting out all of the resistance. The switches underneath contactors 11 and 12 make it impossible for 11 to raise with 12 and 13 or vice versa. The reason for this arrangement is very evident, as a direct ground for R₇ would result.

=The Westinghouse Electro-Pneumatic System of Control.= In this system of multiple unit or train control, the current to the motors is supplied through a set of unit switches or circuit breakers which are sometimes placed in a circular case or turret underneath the car and in other cases are ranged in a row under the car. The opening and closing of these unit switches is done with compressed air acting on a piston in an air cylinder. When the circuit is to be closed, compressed air is admitted behind the piston and forces it down against the tension of a seventy-pound spring, and the contacts are brought together. When the switch is to be opened, the air is let out of the cylinder and the spring forces the piston back. The air supply is obtained from the storage tanks of the air brake system. The valve controlling the air supply to the cylinder of each unit switch is operated by electromagnets which derive current from a seven cell, fourteen-volt, storage battery. The small master controller operated by the motorman, makes and breaks the battery connections to the magnets controlling the air valves.

[Illustration: Fig. 28b. Car Wiring for Westinghouse Control System.]

An advantage of this over other multiple-unit systems is that by the use of battery current the control system is not disturbed by interruptions of the main supply of current. The chief advantage of this is that it makes it possible to reverse the motors and operate them as brakes in emergencies at all times.

The battery is charged from the main line through lamps as resistance, or may be charged by being connected in series with the air compressor motor.

In the accompanying diagram, Fig. 28_b_, there are two batteries shown which are charged in series with the compressor motor. By means of two double-pole, double-throw switches, first one and then the other battery is connected for charging and for service. The battery is charged in shunt with a resistance and a relay is connected in the circuit as shown, so as to open the battery circuit whenever the current through the motor stops, and thus prevent the battery discharging through the resistance.

The master controller has a double set of segments in order to decrease the length of the shaft. The handle, therefore, is moved only one-sixth of a revolution from off to full speed. The various circuits can be traced by the letters and numbers each wire bears, so that the circuits will not be gone over in detail. The first position of the master controller throws the reverser switch in the proper direction and also closes the main circuit breaker. On the second point the motors are connected in series with all resistance in circuit, and these resistances are automatically cut out one by one. On the next point of the controller the motors are in multiple and the resistances are automatically cut out in a similar manner. The automatic cutting out of resistances is accomplished by a limit switch in conjunction with operating and holding coils on the electro-pneumatic valves. This limit switch is a kind of a relay which has the current from one of the motors flowing through its coil and which acts to open a certain battery circuit which operates the electro-pneumatic valves whenever the current in the motor circuit in question exceeds the amount for which the limit switch is set. The automatic acceleration or cutting out of resistance is accomplished as follows:

Each electro-pneumatic valve has two magnet coils, one of which is an operating coil and the other a holding coil for holding the valve open after it is operated. When first the current flows through a circuit to one of the electro-pneumatic valves, it flows through the operating coil and operates the valve to close the corresponding switch or switches of the main circuit by turning the air into the cylinders. As soon as the main switch is closed, it cuts into circuit the holding coil of its corresponding electro-pneumatic valve and this coil will, with the battery current, hold the switch closed even though the circuit to the operating coil may be opened momentarily by the limit switch as each step of resistance is cut out. This prevents the switches from opening when they are once closed and allows the operating coils to open an air valve each time the current through the limit switch coil falls below the amount for which it is set. The contacts which close the holding coil circuit on each valve whenever a main switch is closed, are called interlocks and are indicated on the diagram.

[Illustration: Fig. 29. Diagram of Electric Heaters.]

The main line circuit breaker, which is electro-pneumatically operated, will open automatically on overload and can be reset by the motorman on all the cars of a train by closing a switch located beside each controller.

CAR HEATERS.

=Electric Heaters= for warming cars in winter, consist of iron wire coils which are warmed by the passage of electric current through them. The heat so evolved varies as the resistance multiplied by the square of the current. The iron wire coils of the heater are mounted on non-combustible insulating supports, and are arranged so that there is a free circulation of air through them. The coils are surrounded with a perforated metal case, the object of which is to prevent injury to the coils and to prevent persons or clothing coming in contact with the hot, live wires of the coils. Heaters are sometimes arranged so that they can be connected in series or parallel to give different degrees of heat.

The diagram, Fig. 29, shows the most common arrangement of electric heaters recently. The tap from the trolley should be taken off on the trolley side of the circuit breaker. After passing through a fuse the circuit goes to the switch. Each of the heaters contains two coils, one of higher resistance than the other. Two independent circuits are run from the switch, through the heaters and to the ground. One circuit passes through the high resistance coils of the several heaters while the other goes through the low resistance coils. The switch has three points. On the first point a circuit is made through the high resistance coils. The second point connects the low resistance coils while the third point puts both circuits in service. With this arrangement three gradations of heat may be obtained.

To avoid complicated wiring sometimes but one circuit is employed. In such a case the heat must either be all on or off, no gradations being possible.

The chief difficulty encountered with electric heaters is the breaking of the wires because of the scale of oxide that forms gradually when they are run at a high temperature or because of water striking them from passengers’ clothing on wet days, which causes the wires to snap.

The Consolidated Car Heating Company gives the following data on the current required to heat cars:

====================+=================+================= | Length of Car | Amperes. | Body. +----------------- | |Switch Positions. | +----------------- | | 1 2 3 --------------------+-----------------+----------------- | { 14 to 20 feet | 3 4 7 Average conditions | { 20 to 28 ” | 3 6 9 | { 28 to 34 ” | 4 7 11 | | Severest conditions | { 18 to 24 feet | 4 7 11 | { 28 to 34 ” | 6 8 14 --------------------+-----------------+-----------------

In his Electrical Engineers’ Hand Book, Mr. Foster gives results of tests made on Brooklyn cars as follows:

=========================+================+==================== Cars. | Temperature F. | Consumption. -------+--------+--------+----------------+-------------------- Doors. |Windows.|Contents|Outside.|Average|Watts.| Amperes | | cu. ft.| |in car.| |at 500 volts. -------+--------+--------+--------+-------+------+------------- 2 | 12 | 850½ | 28 | 55 | 2295 | 4.6 2 | 12 | 850½ | 7 | 39 | 2325 | 4.6 2 | 12 | 808½ | 28 | 49 | 2180 | 4.3 2 | 12 | 913½ | 35 | 52 | 2745 | 4.5 4 | 16 | 1012 | 7 | 46 | 3038 | 6. 4 | 16 | 1012 | 28 | 54 | 3160 | 6.3 -------+--------+--------+--------+-------+------+-------------

When not watched carefully considerable current may be wasted by allowing the heaters to remain turned on when not needed. Many companies hang out signs where motormen may observe them, indicating when the heaters shall be turned on and to what point.

[Illustration: Fig. 30. Electric Heater.]

The best practice in electric heating is to have plenty of heaters and run the wire at a low temperature, rather than attempt to heat with a few at high temperature. The greater the number of heaters the larger the radiating surface around which the air can circulate and a given amount of car heating can be accomplished with less current than with a few high temperature heaters. The depreciation of the heater wires is less the lower the temperature at which they are operated. An electric heater is shown in Fig. 30.

=Hot-Water Heaters= are frequently used on large electric cars. Hot-water pipes are placed along the sides of the car, and connected with a stove containing hot-water coils at one end of the car. The water, as it is heated in the stove or heater, expands, and consequently becomes lighter per cubic inch or other unit of volume; it therefore tends to rise when balanced against the colder water in the car pipes. Hot water leaves the top of the heater, flows up to an expansion tank and then down through the car piping, and back to the bottom of the heater. The car piping slopes continuously down from the top connection to the bottom connection of the heater. At the top, an opening to the atmosphere is provided through a small water tank, called an _expansion tank_. This prevents water pressure bursting the pipes as they become heated, and allows any steam that may have formed to escape. The most modern hot-water heaters for cars are completely closed except as to the ash pit at the bottom and a small feed door in the top. The latter is locked so that the fire cannot come out even if the car is tipped over in a wreck. Fig. 31 shows the pipes of a hot-water heating installation.

[Illustration: Fig. 31. Pipes for Hot-Water Heating.]

CAR WIRING.

The wires from motors to controllers, when placed in exposed position under the car, are bunched in cables or covered with hose. In some cases special runways are provided in the bottom of the car to accommodate the car wiring. All the wiring in a car should be heavily insulated with moisture-proof rubber-covered wire, and further protected from mechanical abrasion by a tough outer covering.

Stranded rubber insulated wire is used almost exclusively for wiring all parts of the car. A general idea of the path of the motor circuit wiring may be obtained by reference to Fig. 22. The main lead after leaving the trolley stand is cleated to the trolley board on top of the car. At the end of the car it passes through the roof and to the circuit breaker. On leaving the breaker it is led down a post, through the floor and to the choke coil and lightning arrester underneath the car. It then passes to the trolley terminal of the controller.

The tap for the light wiring (although shown otherwise in the drawing) is usually taken off the main circuit before the circuit breaker is reached. This arrangement allows the lamps to be burned when the circuit breaker is open. After passing through fuses and switches in the motorman’s cab the circuit for the lights is led through the car in moulding concealing it.

The wires running between the motors, controllers and resistance frames underneath the car, as has been stated, are often carried in canvas hose. Usually two cables are made up, for should all the wires necessary be placed in one cable this would become too bulky to be properly cleated up. To make the canvas hose waterproof and to prolong its life it is usually given several coats of asphaltum paint.

The wiring of the new cars of the New York subway is an example of the most advanced practice. All the wires under the cars are carried in “loricated” conduit, which consists of a wrought-iron tube heavily enameled both inside and out. The motor leads and the other larger wires are carried in separate conduits. The conduits are usually hung to the steel beams of the floor framing by strap bolts. This method of wiring gives a reasonable assurance that it will not become defective. Moreover, it lessens fire risk. The conduits are all grounded and should one of the wires come in contact with the conduit carrying it, the dead ground resulting would cause the fuse to blow instantly, and all danger would cease.

RESISTANCES.

The type of resistance now most common for heavy motor equipment is in the form of cast-iron grids, which are assembled together and connected in series. These grids are sufficiently stiff to render unnecessary any solid insulation between them, and hence they can radiate heat to the best advantage. The only difficulty experienced with them is from the warping or cracking. Resistances for lighter equipment are composed of sheet-steel ribbons wound in coils. Each turn of a coil is insulated from the next by asbestos. Other forms of sheet-steel resistance with asbestos insulation between the turns, have also been used. In Fig. 32 is shown a Westinghouse grid type diverter for street railway equipment.

ELECTRIC CAR ACCESSORIES.

=Canopy Switch.= An overhead switch, sometimes called a “canopy switch,” is commonly placed over each street-car platform where a controller is located, usually in the deck or canopy above the motorman’s head. This is simply a single-point switch that may be used by the motorman to cut the trolley current off from the controller wiring so that the controllers will be absolutely dead. When two such switches are used, one on each end of the car, they are connected in series.

[Illustration: Fig. 32. Grid Type of Resistance.]

=Car Circuit Breaker.= Frequently on large equipments an automatic circuit breaker is provided instead of this overhead switch. This circuit breaker can be tripped by hand to open the circuit whenever desired; and is also equipped with a solenoid magnet, which can be adjusted so that it will trip or open the circuit breaker at approximately whatever current it is set for. This circuit breaker protects the motor and car wiring from excessive current, such as would occur in case of a short circuit in motors or car wiring, or in case the motorman turned on current so rapidly as to endanger the windings of the motors. Circuit breakers, however, are most commonly used on cars having controllers located at only one end in a motorman’s cab.