Publication 2364F-5.05 - March 1999
Testing Components
4-15
Testing MOVs
MOVs provide surge, line-to-line, and line-to-ground protection for the
RGU.
1. Push the disconnect lever to off and wait for all voltage to discharge
from the unit. Do not continue until all voltage has dissipated from the
DC bus.
2. Verify that there is no voltage across the DC bus (see Figure 4.12 and
Figure 4.13 for check points).
3. Observe the MOVs (typically located near the circuit breaker). Replace
any MOVs that are visibly damaged.
Testing Precharge Resistors
The precharge resistors help the RGU supply appropriate voltage to the
internal capacitors during the precharge routine.
1. Push the disconnect lever to off and wait for all voltage to discharge
from the unit. Do not continue until all voltage has dissipated from the
DC bus.
2. Verify that there is no voltage across the DC bus (see Figure 4.12 and
Figure 4.13 for check points).
3. Check the precharge fuses.
4. Set meter to check resistance. Disconnect and check each of the
precharge resistors. Resistors should indicate a resistance of
5.6-6.8 ohms (6 ohm rating).
Note: Older J-code RGU resistors should have a resistance of 26.5-28.0
ohms (27 ohm rating). This resistor is shown in Figure 4.10.
Replace any damaged components and associated wiring, as necessary.
Figure 4.10
Precharge Resistors
6 ohm
Precharge
Resistor
27 ohm
Precharge
Resistor
Used only in older J-code RGUs
