Parker TQ10X, Руководство пользователя

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114 TQ10X User Guide
of oscillation is greater than about 20 Hz. Systems in this power range typically
have resonant frequencies much higher than this. The default settings suggested for
each motor will result in a latched fault after about 3.3 seconds above threshold.
This time can be selected with SW1-4,5,6. The sequence of events is: Current
exceeds threshold, illuminating the
PEAK CURRENT LED (green). If this contin-
ues for longer than 3.3 seconds, the
IN FOLDBACK
LED will illuminate red, and
current will be reduced.
If SW2-1 is ON, then the MOTOR FAULT LED (red) will illuminate. The IN
FOLDBACK
LED may go out when the
MOTOR FAULT
LED turns on, depending
on the load. Current will be reduced to zero and the FAULT OUT will go active.
This setting is recommended for nearly all applications, since it causes a motor
fault to be indicated. In most applications, allowing the current to be reduced by
foldback (without causing a fault) will result in the controller faulting from excess
position error, masking the source of the problem, or in the production of defective
product. The latched drive fault will lead the troubleshooter to the source of the
problem more directly. A mechanical jam, or increased friction in the mechanical
system are the common causes.
An exception to this would be an application where stopping the axis will lead to
unacceptable consequences, and continued motion, even at a reduced rate, is
preferable. An example of this would be a conveyor drive running product through
an oven which is hot enough to melt the product eventually.
The default settings cause the timer to start when the current is approximately
twice the motor’s continuous rating (2 times Ics). The thermal switches in Parker
servo motors will protect a properly mounted motor in its specified ambient
temperature, up to at least twice Ics, at which point foldback takes over. If the peak
current limit is set to three times Ics as recommended, foldback will reduce current
to a level below twice Ics, reducing the rate of motor heating enough to give the
thermal switch time to react, and protect the motor.
Note that foldback is not a substitute for proper sizing of the application, and does not
enforce a lengthy cooling-off period. As soon as the command goes below the actual
current, the circuit starts over. Applications with insufficient dwell time to allow the motor to
cool between periods of peak current will not be successful.
Foldback is intended to be a secondary safety net. Primary protection of the motor
during application problems should be provided by end-of-travel-limit switches,
and by proper setting of position-error faults in the controller. These will provide
quicker, more direct detection of end-stop or mechanical jamming problems in the
application than foldback can. If these systems fail, foldback can generate a fault
(which stops all motor current) or reduce the rate of motor heating to enable the
thermal switch to operate.
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