Application; Signals - ABB RELION 620 Series Technical Manual

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1MAC504801-IB E

620 series ANSI

Technical Manual

Application

When a motor runs with a load connected, it draws a current equal to a value between the

no-load value and the rated current of the motor. The minimum load current can be

determined by studying the characteristics of the connected load. When the current drawn

by the motor is less than the minimum load current drawn, it can be inferred that the motor

is either disconnected from the load or the coupling mechanism is faulty. If the motor is

allowed to run in this condition, it may aggravate the fault in the coupling mechanism or

harm the personnel handling the machine. Therefore, the motor has to be disconnected

from the power supply as soon as the above condition is detected.

37M detects the condition by monitoring the current values and helps disconnect the

motor from the power supply instantaneously or after a delay according to the

requirement.

When the motor is at standstill, the current will be zero and it is not recommended to

activate the trip during this time. The minimum current drawn by the motor when it is

connected to the power supply is the no load current, that is, the higher pickup value

current. If the current drawn is below the lower pickup value current, the motor is

disconnected from the power supply. 37M detects this condition and interprets that the

motor is de-energized and disables the function to prevent unnecessary trip events.

37M Input signals

37M Output signals

Phase A current

Phase B current

Phase C current

Block all binary outputs by resetting timers

Protection functions

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