Rockwell Automation SA500 DC Bus Supply - Manual (Page 26)

4-2 SA500 DC Bus Supply
4.1.3 The PSM READY LED Is Off
Problem: The DC bus voltage is different from what is expected.
During normal operation, the PSM READY LED is on when AC power is applied and
there are no bus supply faults. If this LED turns off, use the following procedure to
isolate the problem:
Step 1. Using a voltmeter, verify that the DC bus supply is receiving the correct AC
input voltage (terminals L1, L2, L3).
Step 2. If the bus supply is not receiving the correct input voltage, check the AC input
power lines.
If the bus supply is receiving the correct voltage, proceed to step 3.
Step 3. Check the other fault LEDs. the PHASE LOSS and OVERTEMP LEDs should
be off. If either LED is on, refer to the appropriate troubleshooting section in
this chapter.
Step 4. If the PSM READY LED remains off, replace the DC bus supply.
4.2 DC Bus Braking Fuse Is Blown
Problem: SA500 AC Power Module regeneration does not work properly (i.e., braking
is slower than expected) and the Power Module experiences frequent DC bus
overvoltage faults.
These problems may be caused by a blown braking fuse. Use the following procedure
to determine if the braking fuse is blown:
Step 1. Turn off and lock out AC input power to the bus supply.
Step 2. Wait five minutes to allow the DC bus voltage to dissipate.
Step 3. Measure the DC bus potential across the POS and NEG terminals of the DC
bus supply and each Power Module before working on the unit.
When the DC bus potential is down to less than 5V, touch a 50
Ω,
50 W or
larger resistor across the POS and NEG terminals for 20 seconds to allow
any remaining DC bus voltage to dissipate.
Remove the resistor and re-measure the DC bus potential to ensure the DC
bus capacitors are completely discharged before touching any internal
components.
Step 4. Rotate the quarter-turn cover fasteners to the open position and remove the
bus supply’s front cover.
Step 5. Remove the fuse (see figure 4.1). Use an ohmmeter to check if the fuse is
!
ATTENTION: DC bus capacitors retain hazardous voltages after input
power has been disconnected. After disconnecting input power from the
DC bus supply, wait five (5) minutes and then measure the voltage at the
POS and NEG terminals of the DC bus supply and each Power Module
to ensure the DC bus capacitors are discharged before touching any
internal components. Failure to observe this precaution could result in
severe bodily injury or loss of life.