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Posted by Ken Sterling on April 8, 2008, 9:31 pm
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Not an expert in 3-phase stuff, but familiar with motor starters and
contactors. Have a need to work on a Dough Mixer, which is 3-phase
but the motor is two speed. One motor for the rotating bowl, and a
larger motor for the dough hook. The dough hook motor is two speed.
This is an older Italian machine (no info on it), but after cleaning
the contact tips on the main contactor, got the motor so it will run
on low speed and shut off when it is supposed to. However, this
machine is designed to run for a preset time (owner selected) on low
speed, then kick into high speed for another preselected time.
Problem: Runs on low speed but when it kicks into high speed, starts
to single phase, and trips out. I'm not sure how the motor is made,
and how the wiring through the contactors would be done to accomplish
this. Any links to show a crude schematic? I've been looking without
much luck. Any help appreciated.
Thanks.
Ken.
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Posted by Robert Swinney on April 8, 2008, 10:02 pm
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Ken,
I can't help with a diagram but my advice is to check the motor thoroughly when
disocnnected from
the control box. When you are sure the motor is good on both speeds, then
trouble shoot the control
box.
Bob Swinney
<Ken Sterling (Ken Sterling)> wrote in message
Not an expert in 3-phase stuff, but familiar with motor starters and
contactors. Have a need to work on a Dough Mixer, which is 3-phase
but the motor is two speed. One motor for the rotating bowl, and a
larger motor for the dough hook. The dough hook motor is two speed.
This is an older Italian machine (no info on it), but after cleaning
the contact tips on the main contactor, got the motor so it will run
on low speed and shut off when it is supposed to. However, this
machine is designed to run for a preset time (owner selected) on low
speed, then kick into high speed for another preselected time.
Problem: Runs on low speed but when it kicks into high speed, starts
to single phase, and trips out. I'm not sure how the motor is made,
and how the wiring through the contactors would be done to accomplish
this. Any links to show a crude schematic? I've been looking without
much luck. Any help appreciated.
Thanks.
Ken.
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Posted by pdrahn@coinet.com on April 8, 2008, 10:57 pm
Please log in for more thread options On Apr 8, 6:31 pm, Ken Sterling (Ken Sterling) wrote:
> Not an expert in 3-phase stuff, but familiar with motor starters and
> contactors. Have a need to work on a Dough Mixer, which is 3-phase
> but the motor is two speed. One motor for the rotating bowl, and a
> larger motor for the dough hook. The dough hook motor is two speed.
> This is an older Italian machine (no info on it), but after cleaning
> the contact tips on the main contactor, got the motor so it will run
> on low speed and shut off when it is supposed to. However, this
> machine is designed to run for a preset time (owner selected) on low
> speed, then kick into high speed for another preselected time.
> Problem: Runs on low speed but when it kicks into high speed, starts
> to single phase, and trips out. I'm not sure how the motor is made,
> and how the wiring through the contactors would be done to accomplish
> this. Any links to show a crude schematic? I've been looking without
> much luck. Any help appreciated.
> Thanks.
> Ken.
Check Wiki-answers:
http://wiki.answers.com/Q/How_do_you_wire_a_three_phase_motor_with_two_speed_to_a_three_phase_power_supply
I didn't study it, this may be how your motor is wired.
Paul
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Posted by Bruce L. Bergman on April 9, 2008, 4:56 pm
Please log in for more thread options On Tue, 8 Apr 2008 19:57:24 -0700 (PDT), "pdrahn@coinet.com"
>On Apr 8, 6:31 pm, Ken Sterling (Ken Sterling) wrote:
>> Not an expert in 3-phase stuff, but familiar with motor starters and
>> contactors. Have a need to work on a Dough Mixer, which is 3-phase
>> but the motor is two speed. One motor for the rotating bowl, and a
>> larger motor for the dough hook. The dough hook motor is two speed.
>> This is an older Italian machine (no info on it), but after cleaning
>> the contact tips on the main contactor, got the motor so it will run
>> on low speed and shut off when it is supposed to. However, this
>> machine is designed to run for a preset time (owner selected) on low
>> speed, then kick into high speed for another preselected time.
>> Problem: Runs on low speed but when it kicks into high speed, starts
>> to single phase, and trips out. I'm not sure how the motor is made,
>> and how the wiring through the contactors would be done to accomplish
>> this. Any links to show a crude schematic? I've been looking without
>> much luck. Any help appreciated.
>> Thanks.
>> Ken.
>
>Check Wiki-answers:
>http://wiki.answers.com/Q/How_do_you_wire_a_three_phase_motor_with_two_speed_to_a_three_phase_power_supply
>
>I didn't study it, this may be how your motor is wired.
Another possibility - there's a wire swapped, or most likely the
shorting contacts aren't shorting.
http://www.eng-tips.com/viewthread.cfm?qid=164827&page=1
Will give clues on wiring - you have to swap the feed point to
U2-V2-W2 AND short U1-V1-W1 together to shift into high speed. If the
shunt contacts leave one lead open, that will cause problems.
Tear down all the contactors (again) and inspect the contact points
first. That's often where the trouble lies, one of the contacts has
burned to the point it is going open. And unless it's one of the
European DIN-rail miniature units that you just toss and replace,
almost all motor starters and power contactors have field replaceable
contact kits.
Sometimes you can repair a bad contactor TEMPORARILY by filing off
the contacts flat and smooth, then swapping one half of the contacts
during reassembly - the filed-off bad base contacts now mate with a
good moving shoe, and a bad moving shoe with good base contacts.
The contact swap will only buy you a few days before the trouble
reappears, but it proves where the fault is and gets the gear running.
And that's usually enough time to find and ship the needed parts.
And always check your phasing carefully when you are done, jog it in
each speed before allowing automatic operation - if there's a wire
swapped and the motor tries reversing as it shifts from Low to High
while it is running, this is not good at ALL.
--<< Bruce >>--
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Posted by Ken Sterling on April 9, 2008, 10:31 pm
Please log in for more thread options >On Tue, 8 Apr 2008 19:57:24 -0700 (PDT), "pdrahn@coinet.com"
>
>>On Apr 8, 6:31 pm, Ken Sterling (Ken Sterling) wrote:
>>> Not an expert in 3-phase stuff, but familiar with motor starters and
>>> contactors. Have a need to work on a Dough Mixer, which is 3-phase
>>> but the motor is two speed. One motor for the rotating bowl, and a
>>> larger motor for the dough hook. The dough hook motor is two speed.
>>> This is an older Italian machine (no info on it), but after cleaning
>>> the contact tips on the main contactor, got the motor so it will run
>>> on low speed and shut off when it is supposed to. However, this
>>> machine is designed to run for a preset time (owner selected) on low
>>> speed, then kick into high speed for another preselected time.
>>> Problem: Runs on low speed but when it kicks into high speed, starts
>>> to single phase, and trips out. I'm not sure how the motor is made,
>>> and how the wiring through the contactors would be done to accomplish
>>> this. Any links to show a crude schematic? I've been looking without
>>> much luck. Any help appreciated.
>>> Thanks.
>>> Ken.
>>
>>Check Wiki-answers:
>>http://wiki.answers.com/Q/How_do_you_wire_a_three_phase_motor_with_two_speed_to_a_three_phase_power_supply
>>
>>I didn't study it, this may be how your motor is wired.
>
> Another possibility - there's a wire swapped, or most likely the
>shorting contacts aren't shorting.
>
>http://www.eng-tips.com/viewthread.cfm?qid=164827&page=1
>Will give clues on wiring - you have to swap the feed point to
>U2-V2-W2 AND short U1-V1-W1 together to shift into high speed. If the
>shunt contacts leave one lead open, that will cause problems.
>
> Tear down all the contactors (again) and inspect the contact points
>first. That's often where the trouble lies, one of the contacts has
>burned to the point it is going open. And unless it's one of the
>European DIN-rail miniature units that you just toss and replace,
>almost all motor starters and power contactors have field replaceable
>contact kits.
>
> Sometimes you can repair a bad contactor TEMPORARILY by filing off
>the contacts flat and smooth, then swapping one half of the contacts
>during reassembly - the filed-off bad base contacts now mate with a
>good moving shoe, and a bad moving shoe with good base contacts.
>
> The contact swap will only buy you a few days before the trouble
>reappears, but it proves where the fault is and gets the gear running.
>And that's usually enough time to find and ship the needed parts.
>
> And always check your phasing carefully when you are done, jog it in
>each speed before allowing automatic operation - if there's a wire
>swapped and the motor tries reversing as it shifts from Low to High
>while it is running, this is not good at ALL.
>
> --<< Bruce >>--
>
Thanks for the reply Bruce. I tore down the contactor which was
preventing any operation at all.... it was pretty bad inside (the
machine uses Siemens Minicont contactors) not necessarily fun to get
apart, but do-able. Pretty poor shape inside, but I got it dressed up
and back together good enough to get the machine to fire up. I have
ordered a replacement contactor to get that particular one out of the
pile that's in there, and the machine will run on low without
problems. When the new contactor comes in, I will swap it into the
stack and then try to figure out which one(s) are causing the
high-speed problem. The problem with the Siemens contactors that were
use in this machine is that the only way you can see if they are
pulled in is by looking at a little tiny red tip inside the contactor
face to see if it moves. I'm thinking I may rig up several 120v small
bulbs on leads to connect across the coil terminals to see which
contactors are energized when switching into high gear. There are
probably 7 or 8 contactors in this mess, and no paperwork to help.
Thanks again for the link - I'll check it out, but I'm unfamiliar with
the terminology of U,V,W (1 & 2) as I'm used to working with T1,2,3.
Ken.
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> contactors. Have a need to work on a Dough Mixer, which is 3-phase
> but the motor is two speed. One motor for the rotating bowl, and a
> larger motor for the dough hook. The dough hook motor is two speed.
> This is an older Italian machine (no info on it), but after cleaning
> the contact tips on the main contactor, got the motor so it will run
> on low speed and shut off when it is supposed to. However, this
> machine is designed to run for a preset time (owner selected) on low
> speed, then kick into high speed for another preselected time.
> Problem: Runs on low speed but when it kicks into high speed, starts
> to single phase, and trips out. I'm not sure how the motor is made,
> and how the wiring through the contactors would be done to accomplish
> this. Any links to show a crude schematic? I've been looking without
> much luck. Any help appreciated.
> Thanks.
> Ken.