# Why is a single phase motor not self starting?

Contents

We can easily conclude that the single-phase induction motors are not self-starting because the produced stator flux is alternating in nature and at the starting, the two components of this flux cancel each other, and hence there is no net torque.

## Why are motors not self-starting?

Above a certain size, synchronous motors are not self-starting motors. This property is due to the inertia of the rotor; it cannot instantly follow the rotation of the magnetic field of the stator. Once the rotor nears the synchronous speed, the field winding is excited, and the motor pulls into synchronization.

## How does a single-phase motor start?

Starting Principle

A single phase induction motor consists of a single phase winding on the stator and a cage winding on the rotor. When a 1 phase supply is connected to the stator winding, a pulsating magnetic field is produced. In the pulsating field, the rotor does not rotate due to inertia.

## Are DC motors self-starting?

DC motors are self-starting motors. The armature is stationary, and the magnetic field rotates in the AC motor but in DC motor the armature rotates, and the magnetic field is stationary.

## What is low starting torque?

The starting torque of the motor is given by, … At start, the rotor reactance is large because slip of the motor at start is equal to unity. The large rotor reactance at start makes the starting torque of the motor poor. The motor draws about 5 to 6 times current of its full load current and produce very less torque.

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## Why starter is used in induction motor?

Let us study in detail why starter is required for an induction motor. At starting time, the speed of the motor is zero and slip is at its maximum i.e. unity. So magnitude of the rotor induced emf is very large at start.

## What is the working principle of split phase motor?

Working of Split Phase Motor

At the time of starting, both the main and starting windings should be connected across the supply to produce the rotating magnetic field. The rotor is of a squirrel cage type and the revolving magnetic field sweeps part the stationary rotor, inducing emf in the rotor.