## Direct-on-Line or DOL Starting of Induction Motor

Direct-on-Line or DOL Starting is the simplest mode of starting of Induction Motor where the stator is directly connected to the mains supply as shown in figure below.   The motor starts with its own characteristics. When it is switched on, the motor behaves like a transformer with its secondary, formed by the very low … Read more

## Why does Induction Motor has Poor Power Factor at No Load

Induction Motor when started at no load has very poor power factor in the range of 0.1 to 0.3. For understanding the effect of loading on the power factor of Induction Motor, we will consider three components of current flowing in an Induction Motor namely Magnetizing Current, Stator Loss Component of Current and Load Component … Read more

## Understanding Induction Motor Stability

The concept of stability of Induction Motor is very important and vital for interview point of view or from selection of a particular Induction Motor for a given load. In all Motors, the speed drops if we increase the load torque as the power of Induction Motor is constant (Power = TorquexSpeed). For getting a … Read more

## Auto-Transformer Starting of an Induction Motor

It can easily be seen from the slip torque characteristics of an induction motor that, there is some finite torque when the slip s=1 i.e. speed is zero. This simply means that Induction Motor is a self-starting motor and begins to rotate on its own when connected to a 3 phase supply. At the instant … Read more

## Why Rotor Core Loss is Negligible for Induction Motor?

We have already discussed about losses in electrical machine in “Losses in Electrical Machine – Core Loss”. Under normal operating condition, the core loss in the Rotor of an Induction Motor is negligible. In this post we will discuss about this.     Core loss consists of Hysteresis Loss and Eddy Current Loss. Hysteresis Loss … Read more

## Why Star Delta Starter Preferred in Induction Motor?

The main purpose of any starter is to reduce the requirement of high starting current. Normally the starting current of an induction motor is 6 to 7 times of the full load current. If one has an induction motor with a DOL starter, drawing a high current from the line, which is higher than the … Read more

## Phase Unbalance Fault – Induction Motor

A Phase Imbalance Fault indication on a motor monitor means that the voltage and / or current in one phase winding of the motor is not the same as the other two phases by an amount that exceeds a settable maximum.This means something is wrong and need to be corrected. The most common reason for … Read more

## Cogging in Induction Motor

Cogging phenomenon is observed in Squirrel Cage Induction Motor during starting for certain combination of Stator and Rotor Slots. In Cogging motor fails to start at all. For better understanding a view of Stator Core Laminations, Stator Core and Rotor of Squirrel Cage Induction Motor is shown in figure below. Squirrel Cage Induction Motor Stator … Read more

## Crawling in Induction Motor

Crawling is a phenomenon in which Induction Motor operates at very low speed. Crawling is caused by the presence of space harmonics in the air gap flux. For understanding Crawling, there are some points which are very important to know. Those points are as follows: Speed of Rotating magnetic flux = 2f/P, where f is … Read more