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. 

In article <hk3e2v$cu3$1...@news.albasani.net>,
   pimpom <p...@invalid.invalid> wrote:
> 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. 

Lots on 4QD site about this:
e.g.
http://www.4qd.co.uk/faq/bmnc3.html#machtools  Mains use - (Machine Tools)

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and more!

On Sun, 31 Jan 2010 13:43:18 +0530, pimpom wrote:

> 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.

-- 
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
                                             (Stephen Leacock)

Fred Abse wrote:
> On Sun, 31 Jan 2010 13:43:18 +0530, pimpom wrote:
>
>> 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.

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