bonitron M3452 - Amber DC Bus Light Not on; Blown DC Bus Fuse; Fan Runs Constantly; Fan Doesnt Run

M3452 vR8 EIP/PDP
44
5.3.2. AMBER DC BUS LIGHT NOT ON
This can be a normal condition in systems where DC bus power and logic
control power is applied. This indicates that there is less than 50 VDC on the
inverter bus.
CAUTION!
Do not use this light as an indication that the DC bus is safe to work on!
Always check the DC bus with a working voltmeter before servicing
equipment, as the DC bus light may be broken!
 Use a DC voltmeter to check the bus voltage at the module terminals DC
bus + and DC bus -.
 If the DC bus is above 50VDC, and the light is not on, the light or control
circuit may be damaged, and the unit should be returned for repair.
 The main DC bus fuse may be blown. See next section.
5.3.3. BLOWN DC BUS FUSE
CAUTION!
Do NOT replace a blown DC bus fuse and reapply power to the system
without determining the cause.
This usually indicates serious problems exist and reenergizing the system
can cause significant or catastrophic failure! In most cases, the module will
need to be returned for repair. Contact Bonitron before changing the fuse.
Possible causes for a blown fuse are:
 Shorted heatsink IGBT power transistor.
 Shorted heatsink commutation diode.
 Load bank in use below minimum ohms value.
 Shorted load bank.
 Shorted resistor cabling and or ground fault in cable.
 Operating braking module on a DC bus without inverters present. This is
typically encountered in common bus systems when drives are removed
from service. See Section 7 for more information.
5.3.4. FAN RUNS CONSTANTLY
The fan only runs when the braking module heatsink is hot. If the heatsink is
above 110°F, then the fan runs until the heatsink cools to 80°F. If the ambient
temperature is above 80°F, the fan may run continuously. A constantly
running fan does not indicate a problem with the module. If the heatsink
temperature is below 80°F, the thermostat may be damaged. This will not
affect DC bus regulation.
5.3.5. FAN DOESN’T RUN
The fan only runs when the braking module heatsink is hot. If the heatsink is
above 110°F, then the fan runs until the heatsink cools to 80°F.
If the fan never runs, even when the heatsink is hot or during heavy braking
operation, the module may shutdown on heatsink over-temperature. This
occurs at a heatsink temperature of 160°F. If for any reason the fan does not
appear to be working properly, check the following:
 Input and output fuses on the fan transformer. These will be located on
or around the fan transformer itself.