Class of Insulating Matrials

In this theory, classification of insulation, its types and maximum allowable temperature limits is given. The temperature rise of the electric machine depends upon temperature rise of the insulating materials. The different types of insulating material are classified according to maximum temperature limits.

Duty Cycle of Motor

In this theory, the duty cycle of the machines is discussed. The duty cycle of the motor is given from S1 and S8 whether the load varies or not. If the duty is not given in the name plate, it is assumed S1 ( continuous rating ) duty.

Types of Duty Cycle

Continuous Rating Duty ( S1 )

Thermal Equilibrium

Definition of Thermal Equilibrium

According to IEC ( International Electrochemical Commission ), It is a state when the temperature rises of several parts of the machine do not vary more than a gradient of 2K per hour.

Constant Torque, Constant HP and Variable Torque

 

Constant Torque

• The constant torque remains constant regardless of operating speed. However, HP of motor varies directly with speed.

       T = HP / N

       Where N = Speed in RPM

Automatic Star Delta Starter

Control circuit of automatic star delta starter

The working of automatic star delta starter is explained here. The control circuit of the automatic star delta starter consists of three contactors – main contactor, star contactor and delta contactor. It also required one timer for switching of motor from star to delta operation.

Working of Forward-Reverse Starter

Forward-Reverse Starter Control circuit

In this post, working of forward-reverse Starter Control circuit explained. The forward reverse starter is applicable where frequent forward and reverse of induction motor is necessary. The control circuit of forward-reverse starter consists of two contactors, one for forward direction and other for reverse direction. The complete working of Forward-Reverse Starter is explained in following steps.

Working of Direct ON Line Starter & Control Circuit

Direct on line starter

In this post, the working of direct on line starter is given. It is simplest type of AC starter as it required only one contactor to control the starting current. It is also cheapest starter of all types of AC motor starter.

Semi Automatic Star Delta Starter Control Circuit & Working

Semi-automatic star delta starter

In this post, working of semi-automatic star delta starter is given. It consists of 3 contactors – main contractor, star contactor and delta contact.

Semi-automatic star delta starter control circuit & working

Here the working of semi-automatic star delta starter is explained in steps.

Push on button.