HD65 & HD130 STEPPER DRIVES USER GUIDE 17
Operation of the Drive Protection Systems
There are three basic protection systems built into the drive, and
these guard against damage caused by overloads, power supply
faults and excess temperature. Operation of any of these protection
circuits will de-energise the drive, and the reason for shutdown is
indicated by an LED on the front of the drive. Provided the cause of
the fault has been removed the drive may be re-energised by taking
control terminal 7 to 0v or by temporarily removing power. Figure 7
is a simplified diagram of the protection circuitry.
Overload
Protection
An overload condition may be brought about by incorrect motor
connection, short circuits across the motor terminals or any other
condition causing excess current to flow. It may also arise if a very
low inductance motor is desynchronised during deceleration. In any
of these circumstances the overcurrent comparator will set the fault
latch, turning on the appropriate LED and giving a fault output signal.
Supply
Failure
Protection
Should the high-voltage supply rise excessively, or any of the logic
supply rails fall outside preset limits, the supply protection circuit
comes into operation. It functions by using a comparator to compare
each of the supply rails with fixed reference levels. If the preset
limits are exceeded, the fault latch is set and the supply failure LED
is illuminated. Note that an excessive rise in the high-voltage supply
may result from failure of the power dump fuse FS2.
Over-
temperature
Protection
This mode of shutdown occurs if the heatsink temperature reaches
85°C, which will generally be the result of inadequate cooling. The
heatsink temperature is monitored by a thermal sensor mounted on
the drive pcb. The output from the sensor sets the fault latch
directly, and illuminates the Overtemperature LED. It will be
necessary to allow time for the drive to cool down before it can be
reset.