Shunt Wound Motors

What is a shunt wound motor? DC shunt motors have constant speed characteristics, the difference between no load and full load speed being between 10% and 20% of the rated speed. Suitable for reversing as standard with 4 leads brought out of the motor casing (two armature and two field). Speed can be controlled by means of a variable resistance in series with the armature by a ratio of approximately 6:1, however this can vary considerably depending on the application. Alternatively, if an AC supply is available a speed range of up to 25:1 can be obtained by means of a D.C. thyristor controller. Important: It must be noted, when reducing the motor speed the armature cooling fan efficiency drops and therefore it is recommended to reduce the rating or load of the motor by 30–40% over a speed range of 10:1 and by 50% for a speed range of 25:1.