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A large size 8803 Omegapak drive displays overcurrent fault without the dot (OCF). At this point, the current feedback is suspected. How is the DC bus current sensor checked?

Follow steps outlined below in sequential order:

Step 1:
Disable output phase detection and run unit with no motor.  

Step 2:
If it still trips, check following voltages on measurement board terminals:
Sensor power supply:
J4-1 to J4-3 = 31vac
J4-1 to J4-2 = 15vac
J4-3 to J4-2 = 15vac
If these voltages are wrong, isolate components (e.g., current sensor, other boards, etc.) and recheck.  If problem stays after isolating compoenents, suspect either power board or transformer.

Step 3:
If everything checks good, check:
LM+ to J4-2 = 22vdc
LM- to J4-2 = -22vdc
LM+ to LM- = 44vdc
If these do not check good, isolate LEM & recheck. If they now check good, suspect LEM.

Step 4:
If they previous measurements check good, then check:
LM to J4-2 = 0vdc (Sensor output)
This is the output of the LEM & should be zero unless a current is being drawn.  If it is not zero, suspect LEM impedance is unbalanced.

Step 5:
Measurement board power supply
J6-1 to J6-3 = 22vac
J6-1 to J6-2 = 11vac
J6-3 to J6-2 = 11vac
VPP to J6-2 = 15vdc
VPN to J6-2 = -15vdc
VPP to VPN = 30vdc
Isolate as needed.  If isolated & voltages correct, then suspect measurement board.

CTA-ID : 1678
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