QM range App Note, document number 260283, rev 15
Page 34 of 48
POWER SUPPLY PROTECTION
No Load Operation
The power supply will operate with no load on the output with no damage or hazardous condition.
Overload and short circuit protection
An overload or short circuit condition on the output(s) will cause no damage to the power supply. The power
supply may attempt to restart until the overload or short circuit is removed. After removal of the overload or
short circuit, the power supply will automatically resume normal operation.
Any output or module may latch off with a hard short applied across the output terminals, requiring an on/off
ac cycle to reset.
Over temperature protection
Main converter: In the event of the temperature rising beyond specified limits, the QM power supply
converter will turn off, excluding the Standby voltages. Once normal temperatures are resumed, the QM will
automatically resume normal operation.
Standby supplies: If overheating occurs then this will turn off. Once normal temperatures are resumed, the
QM will automatically resume normal operation.
DH module: If overheating occurs, Channels 1 and 2 will turn off and the AC will need to be recycled.
DM module: If overheating occurs, Channels 1 and 2 will turn off and the AC will need to be recycled. If
overheating occurs only on the Channel 2 secondary the module will automatically restart when once
normal temperatures are reached.
SB, SC, Z & Y module: If overheating occurs, The output will turn off and the AC will need to be recycled
Over voltage protection
An overvoltage on the output will cause the output module to shut-down. To restart, remove the ac supply for
a minimum of 10 seconds and then reapply. Note, an overvoltage on the standby supplies will require the ac
to be removed for several minutes before restarting the unit.
8.
COOLING REQUIREMENTS
The QM series has internal variable speed cooling fans. A minimum clearance of 50mm should be provided at
the input and output ends to allow air to enter and exit the power supply.
If other fans are used in the system, ensure that the QM airflow direction is in the same direction. Failure to do
this can result in the power supply overheating due to low air pressure.
