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PS for PWM-controlled motor

P

pimpom

Jan 1, 1970
0
I don't know if this should be in seb rather than in sed, but
here goes. I have this brushed motor from an old machinery with
an integral reduction gear. The label has faded completely so
that it's impossible to read the nameplate ratings. It was
powered from a transformer that outputs 26.5V at no load, and
judging from the orginal control board, it was apparently run by
phase control at mains frequency with a pair of SCRs. The current
limiting jumper was set at 3A. The transformer is rated for 90VA,
secondary dc resistance is about 0.2 ohm and primary (230V) 12
ohms.

I'd like to try using the motor and the transformer with
high-frequency PWM control, but if I rectify and filter the
transformer output, the supply voltage will be substantially
higher than the average in the original scheme (though of course
no higher than the peak). Is this likely to cause any problems?
Please ignore any other issues for the time being.
 
F

Fred Abse

Jan 1, 1970
0
I don't know if this should be in seb rather than in sed, but here goes. I
have this brushed motor from an old machinery with an integral reduction
gear. The label has faded completely so that it's impossible to read the
nameplate ratings. It was powered from a transformer that outputs 26.5V at
no load, and judging from the orginal control board, it was apparently run
by phase control at mains frequency with a pair of SCRs. The current
limiting jumper was set at 3A. The transformer is rated for 90VA,
secondary dc resistance is about 0.2 ohm and primary (230V) 12 ohms.

I'd like to try using the motor and the transformer with high-frequency
PWM control, but if I rectify and filter the transformer output, the
supply voltage will be substantially higher than the average in the
original scheme (though of course no higher than the peak). Is this likely
to cause any problems? Please ignore any other issues for the time being.

If you implement proper current, as opposed to voltage, control, it
shouldn't matter. You could then use armature voltage for speed feedback.
Just limit maximum speed to that giving, say 24V on the armature.
 
P

pimpom

Jan 1, 1970
0
Fred said:
If you implement proper current, as opposed to voltage,
control, it
shouldn't matter. You could then use armature voltage for speed
feedback. Just limit maximum speed to that giving, say 24V on
the
armature.

Thanks. I thought no one else was going to reply and stopped
watching the thread until now.
 
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