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Posted by Richard on April 1, 2008, 4:59 pm
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Does anyone know the internal connections for a three speed, three
phase motor? I do not mean a motor driven by an inverter.
I'm guessing that it's done by effectively changing the number of
poles the motor 'sees', but I don't _know_ and haven't been able to
find any reliable information.
TIA
Richard
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Posted by NoSpam on April 1, 2008, 6:44 pm
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Richard wrote:
> Does anyone know the internal connections for a three speed, three
> phase motor? I do not mean a motor driven by an inverter.
>
> I'm guessing that it's done by effectively changing the number of
> poles the motor 'sees', but I don't _know_ and haven't been able to
> find any reliable information.
>
> TIA
> Richard
Yes, I have a Holbrook C10 with a 3 speed motor - 3 separate star
connections. Motor speeds are 925, 1430 & 2850 RPM
Dave
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Posted by Christopher Tidy on April 1, 2008, 11:33 pm
Please log in for more thread options NoSpam wrote:
> Richard wrote:
>
>> Does anyone know the internal connections for a three speed, three
>> phase motor? I do not mean a motor driven by an inverter.
>>
>> I'm guessing that it's done by effectively changing the number of
>> poles the motor 'sees', but I don't _know_ and haven't been able to
>> find any reliable information.
>>
>> TIA Richard
>
>
> Yes, I have a Holbrook C10 with a 3 speed motor - 3 separate star
> connections. Motor speeds are 925, 1430 & 2850 RPM
This is what I've seen too, but I believe there are also motors with
tapped windings rather than separate windings.
If you can provide a picture of the terminal box, that might help us to
know what type of motor you've got.
Best wishes,
Chris
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Posted by Richard on April 12, 2008, 6:32 am
Please log in for more thread options <snip>
>>
>> Yes, I have a Holbrook C10 with a 3 speed motor - 3 separate star
>> connections. Motor speeds are 925, 1430 & 2850 RPM
>
>This is what I've seen too, but I believe there are also motors with
>tapped windings rather than separate windings.
>
>If you can provide a picture of the terminal box, that might help us to
>know what type of motor you've got.
>
>Best wishes,
>
>Chris
Thanks for the response. There are 10 wires from teh motor and I have
now measured the various continuities and resistances and concluded
that there are two sets of windings.
Low speed (940rpm) is simple star.
Medium (1400) is delta on tapped windings
High (2800) is star-star on the tapped windings
I've had the motor apart and it looks just possible I may be able to
access the star and other interconnection points. However I've
remembered I still have a pre-historic solid? state inverter/converter
thing. It's a solid slab of transformers and capacitors about 12"x9"
and 30" tall weighing about 1cwt.
It's got a heap of screwed links and tappings that have to be selected
for a given motor, so it's not very user friendly. But as this is the
only machine I have with this sort of motor I'll give it a try first
as it's probably better than risking wrecking a good motor picking it
apart.
Cheers Richard
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Posted by Robert Wilson on April 12, 2008, 8:09 am
Please log in for more thread options Richard wrote:
> <snip>
>>> Yes, I have a Holbrook C10 with a 3 speed motor - 3 separate star
>>> connections. Motor speeds are 925, 1430 & 2850 RPM
>> This is what I've seen too, but I believe there are also motors with
>> tapped windings rather than separate windings.
>>
>> If you can provide a picture of the terminal box, that might help us to
>> know what type of motor you've got.
>>
>> Best wishes,
>>
>> Chris
> Thanks for the response. There are 10 wires from teh motor and I have
> now measured the various continuities and resistances and concluded
> that there are two sets of windings.
> Low speed (940rpm) is simple star.
> Medium (1400) is delta on tapped windings
> High (2800) is star-star on the tapped windings
>
> I've had the motor apart and it looks just possible I may be able to
> access the star and other interconnection points. However I've
> remembered I still have a pre-historic solid? state inverter/converter
> thing. It's a solid slab of transformers and capacitors about 12"x9"
> and 30" tall weighing about 1cwt.
>
> It's got a heap of screwed links and tappings that have to be selected
> for a given motor, so it's not very user friendly. But as this is the
> only machine I have with this sort of motor I'll give it a try first
> as it's probably better than risking wrecking a good motor picking it
> apart.
>
> Cheers Richard
Sounds to me like is wired with different numbers of poles, which
dictate that the speeds are roughly multiples of each other.
Rob.
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> phase motor? I do not mean a motor driven by an inverter.
>
> I'm guessing that it's done by effectively changing the number of
> poles the motor 'sees', but I don't _know_ and haven't been able to
> find any reliable information.
>
> TIA
> Richard