Series wound motors
Series wound motors can be wound for either AC or DC supply, when units are wound for AC supply, they will have an approximate 15% increase in output compared to a DC wound unit running at similar voltage.
Our series motors are designed for reversing as standard with 4 leads out of the motor casing (two armature and two field), with a 3-lead reversing (split field) option also available. In a split field operation, the motor runs on one field coil at a time with approximately 30% power loss, with a change of direction being affected by a single pole switch.
When in operation, the speed of a series wound motor varies inversely with the load. Consequently, this means that they should not be oversized for their application as this will result in the motor running at much higher speeds than required. It is possible to control the speed of this type of motor by means of a variable resistance transformer in a of ratio 5:1, although this can vary depending on the application.
Shunt wound motors
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.