Direct Current (D.C) motor field windings

D.C motor is the one of common application for industrial.It have several advantage compare with A.C motor.Dc motors applied for the momentarily deliver rated around three or more times from their torque.

It also include with dynamic braking function  or regenerative braking to obtained with dc motors for quick stops application.This function can avoid for reducing the size of a mechanical brake.

This time i want share information about D.C. motors field winding.It normally are divided into three classes for our application and need to selected to match for our operation functional.

What are types of winding for DC motor?

1. Series-wound motor.

In this type the field is in series with the armature. This type of motor is only used for direct coupling and other work where the load is permanently coupled to the motor.

Series wound motors have the armature connected in series with the field. While it offers very high starting torque and good torque output per ampere, the series motor has poor speed regulation.

Speed of DC series motors is generally limited to 5000 rpm and below. Series motors should be avoided in applications where they are likely to lose there load because of their tendency to “run away” under no-load conditions. These are generally used on crane and hoist applications.

2. Shunt-wound motor.

In this case the field is in parallel with the armature and the shunt motor is the standard type of d.c. motor for ordinary purposes. Its speed is nearly constant,falling off as the load increases due to resistance drop and armature reaction.

Shunt wound motors, with the armature shunted across the field, offer relatively flat speed-torque characteristics. Combined with inherently controlled no-load speed, this provides good speed regulation over wide load ranges.

While the starting torque is comparatively lower than the other DC winding types, shunt wound motors offer simplified control for reversing service

3. Compound-wound motor.

This is a combination of the above two types. There is a field winding in series with the armature and a field winding in parallel with it.

The relative proportions of the shunt and series winding can be varied in order to make the characteristics nearer those of the series motor or those of the shunt-wound motor.

The typical speed-torque curve is shown in the diagram.Compound-wound motors are used for cranes and other heavy duty applications where an overload may have to be carried and a heavy starting torque is required.

Stabilized shunt motors utilize a field winding in series with the armature in addition to the shunt field to obtain a compromise in performance between a series and shunt type motor.

This type offers a combination of good starting torque and speed stability. Standard compounding is about 12%. Heavier compounding of up to 40 to 50% can be supplied for special high starting torque applications, such as hoists and cranes.