Question

What is the advantage of using an electronic overload on a large hermetic compressor and how does the electronic overload sense that this motor is overloading?

Answer 1

During starting the compressor motor draws huge amount of current for short period of time.So normal overload relay can not avoid this high starting current.But the elctronic relay can make a smooth start for the motor.Also there are many advantages of electronic overload relay

1.Greater sensitivity and high pickup ratio

2.Availability of fault data and disturbance record. Helps analysis of faults.

3.It has selectable trip class

4.High accuracy and also have features of ground fault protection

5.Very fast action.

6.Easy trouble shooting of fault

Electronic overload relays has inuilt current trans- former to sense the motor current. The conductor that supplies power to the motor passes through the core of a toroid transformer . As current ?ows through the conductor, the alternating magnetic ?eld around the conductor induces a voltage into the toroid transformer. The amount of induced voltage is proportional to the amount of current ?owing through the conductor. The voltage induced into the toroid transformer is transmitted through a connected electronic interface that provides the time delay necessary to permit the motor to start. Electronic overload relays are programmable and can be set for the amount of full load motor current, maximum and minimum voltage levels, percentage of overload, and other factors.