Motor Overload Relays - ETI PI-800 Instruction Manual

Electrical Test Instruments PI-800 and PI-1600
Section IV - Operating Instructions
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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 test-
ing or relocation according to steps 19 through 23 in pre-test installation
and setup outlined above.

MOTOR OVERLOAD RELAYS

The motor overload relay is designed to provide overload protection for a mo-
tor; 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 "oper-
ates". It is the opening of these control circuit contacts that deenergizes the
motor starter holding coils, thus allowing the starter contactors to open, shut-
ting down the motor.
Timing Tests
1. Consult the relay manufacturer's literature to determine any necessary
precautions and the expected timing test results. The test current should
be 3 to 4 times the rating of the relay operating coil or heater.
2. Follow steps 1 through 17 in pre-test installation and setup, as required, to
set up the breaker test set.
3. Setup MAC-21 for C.L. Maint (MAINTAIN on).
4. Set MAC-21 RANGE to lowest range that is greater than desired test cur-
rent.
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