Controllers
Parameter manual b maXX BM5800
Document No.: 5.16029.03 Baumüller Nürnberg GmbH
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of 814
3.7
3.7.3.6 Pulse Width Modulation
Switching between Space Vector Modulation (SVM) and Modified Space Vector
Modulation (MSVM).
With MSVM it is possible to reduce the average switching frequency of the IGBTs by a
third, with the result that the average switching losses are also reduced by a third. With a
high duty cycle, it is particularly advantageous to use the modified SVM process (MSVM).
With a smaller duty cycle it is certainly also possible to reduce the switching losses by a
third, but the switching current ripple can be up to twice as great as with normal SVM.
The lower the stator frequency becomes, the more slowly the current space vector ro-
tates. In the extreme case it can even be stationary. For the IGBTs in the three half bridg-
es, the concept of average thermal loading can no longer be used here as for a higher
stator frequency. For certain IGBTs it is then also no longer possible to reduce the losses
with this procedure.
Parameter Z47.40– PWM MSVM Threshold is used to select the PWM duty cycle from
which MSVM is activated.
This parameter can be set from 0.00% to 100%. A value of 0.00% corresponds to zero
voltage at the inverter output; 100% corresponds to 100% PWM duty cycle. From a duty
cycle of 80% the switching losses are reduced by a third with MSVM, without increasing
the switching current ripple compared to SVM.
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