ABB BALDOR BC155, Installation & Operating Manual, Page: 11 / 16

2-5 MN705
Notes:
1. Excessive IR compensation will cause unstable operation and cogging.
2. If using tachometer feedback, the IR trimpot should be set to minimum, fully counterclockwise.
Current Limit Trimpot (CL)
The CL trimpot sets the current limit, (overload), which limits the maximum current, (torque), to the
motor. The CL trimpot is factory set to 1.5 times (150%) the full load rating. To increase the current
limit value, rotate the CL trimpot clockwise. To decrease the current limit value, rotate the CL trimpot
counterclockwise. Some applications may require a lower torque limit value to prevent damage to the
process material or the driven equipment.
Caution: Adjusting the CL above 150% of motor rating can cause overheating and possibly demagnetization of
some PM motors. Consult motor manufacturer.
To Recalibrate the CL trimpot:
1. Disconnect the AC power and connect a DC ammeter in series with either motor armature lead.
Observe correct polarity.
Note: An AC ammeter can be used by connecting it in series with either AC line input lead.
2. Set the main speed potentiometer to approximately 30 – 50% clockwise position.
3. Load the motor shaft in accordance with application requirements.
4. Set the CL trimpot fully counterclockwise. Apply AC input power. The red CL LED will illuminate.
5. While observing the ammeter, rotate the CL trimpot clockwise until the desired current, (torque),
value is obtained. If using an AC ammeter the measured current value will be approximately 75%
of the DC current value.
Note: On cyclical loads, it may be normal for the CL LED to momentarily flash.
Troubleshooting
Table 2-3 Troubleshooting Guide
Indication / Symptom Possible Cause / Solution
Motor does not run.
AC input voltage not present at L1, L2 terminals. Verify correct wiring.
Blown line fuse or tripped circuit breaker. Blown armature fuse or control
circuit fuse. Replace blown fuse with SL-40 or equivalent. If fuse blew due
to miswiring, power bridge module may be defective.
Motor is not running. Power ON LED
is illuminated.
Check ENABLE or INHIBIT circuit for loose or disconnected wiring.
Main speed pot is set to zero. Re-adjust to desired speed.
Main speed pot, speed reference signal input, or motor connections are
open. Verify there are no loose or disconnected wires.
Motor hums or runs at very low speed.
Motor slows when load is applied. CL
LED is illuminated.
Incorrect motor wiring. Verify correct wiring.
Motor is overloaded. Check motor current with DC ammeter. Reduce load.
Motor may be defective. Check motor for shorts or grounds. Check brushes.
Current Limit (CL) trimpot may not be set correctly. Re-adjust CL trimpot
in accordance with section 5.2.6.
Motor runs at high speed and does not
respond to main speed pot or speed
reference signal.
Check field wiring. If using tachometer feedback, check tachometer signal.