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Section 1
General Information
B-2 Adjustments MN894
Example: 3 phase Motor rated at 50 HP at 460VAC, 65 amps (continuous), code letter J.
I
Inrush
+
ǒ
7.5 x 50 x 577
460
Ǔ
+ 470Amperes
Circuit Breaker AdjustmentThe calculated Inrush Amps value is used to initially set the breaker. If the circuit breaker
trips during use, the trip level is increased. Refer to Figure B-1.
Caution: The trip level of the circuit breaker must remain as low as possible
to avoid damage to equipment. If set too high, the circuit breaker
may not trip during a high overcurrent condition.
1. Refer to the manufacturers literature or the rating label on the circuit breaker.
Determine the correct setting of the Trip Level adjustment based on the
calculated Inrush Amps. Set the Trip Level adjustment to this initial level.
2. Turn on power and start the motor.
3. If the breaker trips and the shunt trip indicator on the LCM soft start control
module is OFF, the circuit breaker tripped for an overcurrent condition. Turn
power off and set the Trip Level to the next greater setting.
4. Turn on power and start the motor.
5. If the breaker trips, repeat steps 3 and 4. If the Trip Level adjustment is at the
maximum setting and you have verified there is no phase to phase or phase to
ground shorts, perform step 6. If the shunt trip causes the breaker to trip, refer
to Troubleshooting Section 5 of this manual.
6. If the breaker continues to trip due to inrush current (and not a short circuit) the
Rating Plug may be replaced with one that has a greater current rating. Refer
to the circuit breaker manufacturers information and ratings.
Figure B-1 Magnetic Circuit Breaker
ON
Tripped
OFF
Reset
Handle
Rating Plug
Manual Trip
Trip Level
Shunt Trip Device
Shunt Trip Wires to
LCM soft start module