Motor Overload Relays - ETI PI-6000 Instruction Manual

Electrical Test Instruments PI-6000
Section IV - Operating Instructions
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13. Repeat the above test for the other poles of the circuit breaker.
14. If trip settings were modified for test purposes, restore them to their
original values.
15. Shut down test set, disconnect breaker, and prepare for subsequent
testing or relocation according to steps 18 through 22 in pre-test
installation and setup outlined above.
Instantaneous Trip Time Test
1. Perform Instantaneous Pickup Test as outlined above.
2. Adjust controls to obtain current above pickup, at approximate desired
multiple of rating.
3. Close breaker under test.
4. Press the INITIATE button. Breaker should trip instantaneously.
5. Read and record timer and ammeter readings as instantaneous trip time
and current.
6. Repeat the above test for the other poles of the circuit breaker.
7. Shut down test set, disconnect breaker, and prepare for subsequent
testing or relocation according to steps 18 through 22 in pre-test
installation and setup outlined above.

MOTOR OVERLOAD RELAYS

The motor overload relay is designed to provide overload protection for a
motor; therefore, it offers only one time/current characteristic, which is
essentially a long-time delay. It may be multi-pole; however, most relays are
single pole. In the case of a multi-pole device each pole is tested individually as
in the case of a multi-pole direct acting circuit breaker.
The motor overload relay contains two separate circuits. The current carrying
circuit which contains the relay's operating coil or heater. The control circuit
which contains a set of contacts; these contacts open when the relay
"operates". It is the opening of these control circuit contacts that deenergizes
the motor starter holding coils, thus allowing the starter contactors to open,
shutting down the motor.
Timing Tests
1. Consult the relay manufacturer's literature to determine any necessary
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