The brush holders are so mounted that the brushes occupy a fixed position relative to the armature. The armature is removed by lowering it with the wheels and axle upon which it is mounted. This can be done without disturbing the fields of the motor.
95 TON ELECTRIC LOCOMOTIVE FOR NEW YORK CENTRAL RAILROAD.
General Electric Company.
CONTROLLERS.
In an ordinary electric car, current is taken from the wire through the trolley wheel and pole, and is first led from the trolley base through overhead switches or a circuit breaker, and then to the controller, from which it passes through the motors and thence through the motor frames, car truck, and wheels to the rails and ground. If the car is designed to be operated from either end, an overhead switch or circuit breaker is placed over each platform of the car so that current can instantly be cut off entirely from the controllers by throwing the switch or circuit breaker at either end of the car.
Fig. 17. Armature Axle and Wheels.
The lighting circuit is run from the trolley base independently of the motor circuit, and has its own switch and fuse box. Current for the lights is taken from the trolley circuit before it reaches the main switches or circuit breakers. Current for electric heaters, if such are used, is likewise taken from a separate circuit. On a 500-volt system five 100-volt lamps are usually connected in series for car lighting. As many multiples of five can be employed as are necessary to light the car.
Rheostat Control. The simplest form of controller is that employed where only one motor is used on a car. A rheostat is placed in series with the motor when started, just as on a stationary motor; and the function of the controller is to short-circuit this resistance gradually until it is entirely cut out and the motor operates with the full voltage. The controller also has a reversing switch by means of which the relative connections of the armature and fields are reversed, which, of course, changes the direction of rotation of the motor armature. Such a simple equipment as this, however, is rarely to be found in practice.
Series-Parallel Control. Single-truck cars usually have two motors, one on each axle; and on such cars a series-parallel controller is the kind usually employed. Diagrams of connections on the various points of a series-parallel controller (Type K6) of the General Electric Company, are given in [Fig. 18].