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Posted by Richard on April 12, 2008, 10:34 am
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On Sat, 12 Apr 2008 13:09:23 +0100, Robert Wilson
>Richard wrote:
>> <snip>
>>
>> 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.
Yes indeed Rob, you're quite right. There are physically 36 poles and
it's configured to run as a 2, 4 or 6 pole motor at high, medium or
low RPM. The switch has zillions of terminals and interconnections to
to re-configure the windings to run at the different speeds.
I have two concerns with trying to use my VFD:
Firstly potential damage to the motor during extraction of the
inteconnection tappings.
Secondly, the middle speed is delta connected to 415V. Each winding is
two windings in series which are switched into parallel with the line
to the centre tap and both ends being the star points to become the
star-star for high speed.
Assuming I can get the interconnections out, I could connect the YY as
DD and run it from the VFD for high speed, but I can't quite get my
head round whether I could do the same for the mid speed having
swapped the polarity of one winding of each pair(phase).
I think I probably can, but high power electrical machines was only a
one unit course nearly 30 years ago......
Richard
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Posted by Robert Wilson on April 14, 2008, 4:35 am
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Richard wrote:
> On Sat, 12 Apr 2008 13:09:23 +0100, Robert Wilson
>
>> Richard wrote:
>>> <snip>
>
>>> 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.
>
> Yes indeed Rob, you're quite right. There are physically 36 poles and
> it's configured to run as a 2, 4 or 6 pole motor at high, medium or
> low RPM. The switch has zillions of terminals and interconnections to
> to re-configure the windings to run at the different speeds.
>
> I have two concerns with trying to use my VFD:
>
> Firstly potential damage to the motor during extraction of the
> inteconnection tappings.
>
> Secondly, the middle speed is delta connected to 415V. Each winding is
> two windings in series which are switched into parallel with the line
> to the centre tap and both ends being the star points to become the
> star-star for high speed.
> Assuming I can get the interconnections out, I could connect the YY as
> DD and run it from the VFD for high speed, but I can't quite get my
> head round whether I could do the same for the mid speed having
> swapped the polarity of one winding of each pair(phase).
>
> I think I probably can, but high power electrical machines was only a
> one unit course nearly 30 years ago......
>
> Richard
Hi,
If it is a fairly intelligent drive then you should be able to put into
the drive the number of poles via a menu parameter.
What suppy are you running the drive from? Not sure I can really
comment with any confdence without seeing a diagram.
Most people are trying to run the drive from a asingle phase supply with
a VFD, but then wonder why things are unpredictable when you try and run
a 415 volt motor from it. You know you can turn a 400v machine into a
200v one by re-wiring the motor for delta. Don't forget the current
will go up, but the torque will stay the same, just the speed will reduce.
Is that of any help or am I waffling?
Rob.
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Posted by Peter A Forbes on April 14, 2008, 7:23 am
Please log in for more thread options On Mon, 14 Apr 2008 09:35:59 +0100, Robert Wilson
>Hi,
>If it is a fairly intelligent drive then you should be able to put into
>the drive the number of poles via a menu parameter.
>
>What suppy are you running the drive from? Not sure I can really
>comment with any confdence without seeing a diagram.
>
>Most people are trying to run the drive from a asingle phase supply with
>a VFD, but then wonder why things are unpredictable when you try and run
>a 415 volt motor from it. You know you can turn a 400v machine into a
>200v one by re-wiring the motor for delta. Don't forget the current
>will go up, but the torque will stay the same, just the speed will reduce.
>
>Is that of any help or am I waffling?
>
>Rob.
The Ward 2A at home has a two-speed motor with a mechanically switched
arrangement:
http://www.oldengine.org/members/diesel/Ward/Ward10.jpg
It's all been connected since the picture was taken, but it seems reliable
enough, and I can get details of connections of it, if it would be of any use.
Peter
--
Peter A Forbes
Prepair Ltd, Rushden, UK
peterforbes@prepair.co.uk
http://www.prepair.co.uk
http://www.prepair.eu
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Posted by Richard on April 15, 2008, 4:58 am
Please log in for more thread options On Mon, 14 Apr 2008 12:23:46 +0100, Peter A Forbes
>On Mon, 14 Apr 2008 09:35:59 +0100, Robert Wilson
>
>>Hi,
>>If it is a fairly intelligent drive then you should be able to put into
>>the drive the number of poles via a menu parameter.
>>
>>What suppy are you running the drive from? Not sure I can really
>>comment with any confdence without seeing a diagram.
>>
>>Most people are trying to run the drive from a asingle phase supply with
>>a VFD, but then wonder why things are unpredictable when you try and run
>>a 415 volt motor from it. You know you can turn a 400v machine into a
>>200v one by re-wiring the motor for delta. Don't forget the current
>>will go up, but the torque will stay the same, just the speed will reduce.
>>
>>Is that of any help or am I waffling?
>>
>>Rob.
>
>The Ward 2A at home has a two-speed motor with a mechanically switched
>arrangement:
>
>http://www.oldengine.org/members/diesel/Ward/Ward10.jpg
>
>It's all been connected since the picture was taken, but it seems reliable
>enough, and I can get details of connections of it, if it would be of any use.
>
>Peter
Thanks for the replies chaps. I haddn't considered the 'cleaverness'
of the inverter, but I vaguely recall some mention of poles in the 200
odd parameters that can be set - I'll look into that.
I have also dragged the old inverter contraption from the back of the
barn and will have a play with that. It's a Westinghouse Brake &
Signal Co 'auto-converter'. An auto transformer of sorts with a
considerable slab of capacitors to create a bastard phase - weighs
about 80~100kg!. The data sheet has pre STD phone no's so it's pretty
vintage gear, but if it does work it's easier and less risky than
trying to disconnect the motor windings (to convert from star to
delta) without damaging anything.
I'll try to get so pics on photobucket or somewhere for collective
amusement.
Rgds Richard
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Posted by on April 15, 2008, 12:07 pm
Please log in for more thread options On Tue, 15 Apr 2008 09:58:54 +0100, Richard <sharkface-pilot at
toucansurf dot com> wrote:
snip
>
>Thanks for the replies chaps. I haddn't considered the 'cleaverness'
>of the inverter, but I vaguely recall some mention of poles in the 200
>odd parameters that can be set - I'll look into that.
>
>I have also dragged the old inverter contraption from the back of the
>barn and will have a play with that. It's a Westinghouse Brake &
>Signal Co 'auto-converter'. An auto transformer of sorts with a
>considerable slab of capacitors to create a bastard phase - weighs
>about 80~100kg!. The data sheet has pre STD phone no's so it's pretty
>vintage gear, but if it does work it's easier and less risky than
>trying to disconnect the motor windings (to convert from star to
>delta) without damaging anything.
>
>I'll try to get so pics on photobucket or somewhere for collective
>amusement.
>Rgds Richard
Sounds like a 240V to 415V auto transformer plus phase shift
capacitor to provide the phantom third phase.
These can work quite well but need the capacitor value
(or capacitor voltage tapping) chosen to match the motor
characteristcs.
This means you have a good chance of success on ONE of
the motor speeds (probably the 4 or 6 pole connection) but you
are very unlikely to preserve the 3 speed capability.
Jim
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