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Rockwell Automation Publication 20P-TG001C-EN-P - February 2018
25
Component Test Procedures
Chapter 2
Low or Incorrect Field Current
For a flow chart version of these steps, see Low or Incorrect Field Current Flow
Chart on page
1. Read the General Safety Precautions on page
2. Verify the actual value of parameter 351 [Field Current] by measuring
the DC motor field current using a DC clamp.
3. Verify the following and make any necessary corrections:
• The drive rated field bridge current is set correctly in parameter
374 [Drv Fld Brdg Cur].
• DIP switch S14 is configured to correctly (according to the
instructions in the PowerFlex Digital DC Drive User Manual,
publication
). See Control Board on page
for DIP
switch location.
4. Verify that the value of parameter 280 [Nom Mtr Fld Amps] matches
the rated field current value on motor nameplate and make any
necessary corrections.
5. Remove the protective covers from the drive (see page
6. On the control board, measure the field current signal on the green LA-
LB terminal (LA is the ground and LB is field current signal) and verify
the following:
• The measured value of the field current at LA-LB is equal to the value
of parameter 374 [Drv Fld Brdg Cur].
• The expected voltage across these terminals is 1.66V DC.
For lower field current values, the voltage will be proportional. For
example, if the field is configured for 2 A and the motor is rated for
1.5 A, the measurement at LA-LB will be 1.245V DC (1.5 / x = 2 /
1.66).
• If the voltage measurement is incorrect, continue with step 7.
• If the voltage measurement is correct, but the “Field Current Loss”
fault still exists, replace the control board.
7. By using an ohmmeter, measure the resistance across terminals LA-LB
and verify the following:
• The value equals the equivalent resistance as indicated in this table
(set with DIP switch S14 on the control board).
If the resistance measurement is incorrect, replace the field board.
Field Curr
Scale
Field
Supply
S14-1
S14-2
S14-3
S14-4
S14-5
S14-6
S14-7
S14-8
Equivalent
Resistance
1 A
10 A
OFF
OFF
OFF
OFF
OFF
ON
Not Used
1668
2 A
10 A
OFF
OFF
OFF
OFF
ON
OFF
845
3 A
10 A
OFF
OFF
OFF
OFF
ON
ON
560.9
5 A
10 A
OFF
ON
OFF
OFF
OFF
OFF
333.3
10 A
10 A
ON
OFF
OFF
OFF
OFF
OFF
168.5
13 A
14 A
ON
OFF
OFF
OFF
ON
ON
129.6