Watson-Marlow MM440 - Manual (Page 234)

3 Functions Issue 10/06
MICROMASTER 440 Operating Instructions
234 6SE6400-5AW00-0BP0
Disadvantage
The current ripple is increased when the pulse frequency is reduced. This can
result in an increase of the torque ripple at the motor shaft (for low moments of
inertia) and an increase in the noise level. When the pulse frequency is reduced
this has no influence on the dynamic response of the current control loop as the
current control sampling time remains constant !
¾ Reducing the output frequency (P0290 = 0,2)
This is advantageous if it is not desirable to reduce the pulse frequency or if the
pulse frequency is already set to the lowest level. Further, the load should have
a characteristic similar to that of a fan, i.e. a square-law torque characteristic for
decreasing speed. When the output frequency is reduced, this significantly
reduces the drive inverter output current and in turn reduces the losses in the
power module.
¾ No reduction (P0290 = 1)
This option should be selected if neither a reduction in the pulse frequency nor
a reduction in the output current is being considered. In this case, the drive
inverter does not change its operating point after the warning threshold has
been exceeded so that the drive can be further operated until the shutdown
values are reached. After the shutdown threshold has been reached, the drive
inverter shuts down (trips) with fault F0004. The time which expires up to
shutdown is however not defined and depends on the magnitude of the
overload. Only the warning threshold can be changed in order to obtain an
earlier warning and, if required, externally intervene in the drive process (e.g. by
reducing the load, lowering the ambient temperature).
NOTE
¾
If the drive inverter fan fails, this would be indirectly detected by the
measurement of the heatsink temperature.
¾ A wire breakage or short circuit of the temperature sensor(s) is also monitored.