Industrial Controllers-With Particular Reference to the Control of Direct-Current Shunt Motors

Stating that present day development of motors and controllers is such that former limitations as to regulation of starting current from the viewpoint of motor, controller and supply system have been largely removed, the author presents a series of tests on 15 and 20-h.p., 230-volt, d-c. shunt motors, started from rest. The motors are of two types, constant and adjustable speed. These tests were made to determine: first, the load driven by the motor; second, the power supply; third, the motor operation. From these tests the author concludes, in part; that it is practical with automatic acceleration to use one switch to short-circuit the armature resistor used with motors as large as 15 h. p.; that the shunt field of small adjustable speed motors can be reduced in one step under normal load conditions (this practise can be safely followed up to motors of 50 h. p.); and that adjustable speed motors can use one step resistance for dynamic braking.