Jetter JM-204-480, User Manual, Page: 105 / 126

JetMove 204-480 13 Safe Standstill (Option)
Jetter AG 105
This means that for driving the motor, both inputs Enable1 and Enable2 must be
controlled. At calling up "Safe Standstill", the inputs must be de-energized. This way,
supplying the driver levels and opto isolators will not be necessary any more; the
same way, the DSP will recognise this at the status outputs. This causes the motor
to come to "Safe Standstill".
In a fault condition it is sufficient to only deactivate only one path, as a phase
sequence is not generated any more, if only the "upper" or only the "lower" IGBTs
have been switched off.
For discoupling the control signals of the DSP, especially for excluding a faulty
supply of the driver levels / opto isolator by the control signals of the DSP, all signals
have been equipped with resistors of apt design and values at their interface.
The broken line marks the border between the safety-relevant components.
Fig.: 31: Possible rotation angle in case of defective IGBTs
In the risk analysis, this behavior must be taken into consideration. If this can lead to
a hazard, the function is not apt for use in this case.
The possibility that this occurs is very low, though. If the unit for the failure rate of an
IGBT is 100 fit (10E-7 per hour), the possibility of two IGBTs failing at the same time
is 10E-14 per hour (several million years). Out of these, only 6 out of 15 cases lead
to jerking. This means that practically, there is no possibility of this to happen.
Moreover, the IGBTs are continually being checked at each commutation.
Note!
In spite of these safety precautions, the motor can jerk due to defective IGBTs.
The possible rotation angle depends on the pole pair number of the motion
system in use.
Pole Pair Number of the
Motor
Possible Rotation Angle
1 180°
2 90°
3 60°
5 36°