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Expansion Power Module/Bay "Power and Control Section"
Main AC Input Circuit Breaker: A main AC input circuit breaker is provided to disconnect AC input power from the Expansion
Power Module/Bay's power and control section.
NOTE!
The main AC input circuit breaker has a system controlled trip mechanism to trip the breaker if an EPO signal is sent.
Optional Rectifier AC Input Circuit Breakers: Each rectifier has a separate AC input circuit breaker to disconnect AC input power
from the respective rectifier.
"Output Voltage Present" Indicator: Illuminates green to indicate voltage is present on the Expansion Power Module/Bay's DC
output bus.
"Control Voltage Present" Indicator: Illuminates green to indicate the converter power supply in the Expansion Power Module/Bay
is functioning. (If off when system is in operation, contact Vertiv Technical Support.) (The converter power supply provides 48V DC
for controls.)
3.4 Distribution Panel Lockout/Tagout (LOTO)
The circuit breakers located on a load distribution panel contain a bracket which allows the circuit breaker to be padlocked in the off
position.
3.5 HRMG Configuration Ground Fault (Insulation Fault) Detection Circuit
Operation
Overview
The ground fault (insulation fault) detection circuit in a High Resistance Mid-Point Ground (HRMG) configuration detects the
insulation condition of the positive and negative DC bus to ground.
If a ground fault (insulation fault) is detected, a local indicator illuminates (located on the front of the Main Power Module/Bay's power
and control section). The ground fault (insulation fault) detection circuit also sends a signal to the ACU+ controller which activates
local and remote controller alarms.
High Resistance Mid-Point Ground (HRMG) Configuration Benefits
•
Continuous bus operation with a single pole ground fault (insulation fault).
However; it is important to locate and isolate any ground faults (insulation faults) that occur in order to preserve these benefits. The
voltages between the +Bus and –Bus will shift when a ground fault or insulation breakdown occurs and benefits above will be negated.
In the extreme case, the voltage on an ungrounded pole may be elevated to 400V DC and present a safety hazard to personnel.
Ground Fault (insulation Fault) Detection Alarms
The ground fault (insulation fault) detection circuit monitors for three different types of ground faults (insulation faults).
•
Missing Ground: The HRMG grounding lead that exits each Power Module/Bay power and control sub-rack is not
connected to ground.
•
Ground Fault (Insulation Fault) Alarm: The resistance between the +Bus to ground OR the –Bus to ground is less than the
"Ground Fault (Insulation Fault) Alarm Limit" parameter set in the ACU+ controller. The default setting for this parameter is
39.2k Ohm.
NOTE!
The "Normal Operation Site" impedance to ground for both the positive and negative output to ground should be
determined. Set the Ground/Insulation setpoint below your site's impedance to ground value. See UM1M820NNB-3 for
instructions on how to set this parameter.
Proprietary and Confidential © 2022 Vertiv Group Corp.
Vertiv™ NetSure™ 400V DC Power System User Manual
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