# What are separately excited DC motors used for?

## What are separately excited DC motors used for?

Separately excited DC motors are often used as actuators in trains and automotive traction applications. For their constant speed characteristics, shunt DC motors are used in fixed speed applications such as fans. square of armature current), they can be used in applications that require high starting torque.

## How do you control a separately excited DC motor?

2 Speed control techniques in separately excited dc motor: i) Varying the armature voltage in the constant torque region. ii) In the constant power region, field flux should be reduced to achieve speed above the rated speed.

How do you calculate the speed of a separately excited DC motor?

Speed – armature current (N – Ia) characteristics: We know that speed of dc motor is proportional to back emf / flux i.e Eb / φ . When load is increased back emf Eb and φ flux decrease due to armature resistance drop and armature reaction respectively .

### What is a separately excited DC generator?

A DC generator whose field winding or coil is energised by a separate or external DC source is called a separately excited DC Generator. The flux produced by the poles depends upon the field current with the unsaturated region of magnetic material of the poles.

### What makes a separately excited DC motor separately excited?

Separately excited dc motor has field coils similar to that of shunt wound dc motor. The name suggests the construction of this type of motor. Usually, in other DC motors, the field coil and the armature coil both are energized from a single source. The field of them does not need any separate excitation.

How are shunt wound DC and separately excited DC motor similar?

Both in shunt wound dc motor and separately excited dc motor field is supplied from constant voltage so that the field current is constant. Therefore these two motors have similar speed -armature current and torque – armature current characteristics. In this type of motor flux is assumed to be constant.

## Can a DC motor have both field and armature coils?

Usually, in other DC motors, the field coil and the armature coil both are energized from a single source. The field of them does not need any separate excitation. But, in separately excited DC motor, separate supply Provided for excitation of both field coil and armature coil. Figure below shows the separately excited dc motor.

## How are speed and torque of a DC motor similar?

Therefore these two motors have similar speed -armature current and torque – armature current characteristics. In this type of motor flux is assumed to be constant. • Speed – armature current (N – Ia) characteristics: We know that speed of dc motor is proportional to back emf / flux i.e Eb / φ .