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nuckolls.bob(at)aeroelect
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 Posted: Sun Feb 14, 2021 1:26 pm Post subject: A 3 phase AC (Alternating Current) question |
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At 02:00 PM 2/14/2021, you wrote:
| Quote: | --> AeroElectric-List message posted by: "donjohnston" <don(at)velocity-xl.com>
Looking for some solutions on a project.
I have a lathe/mill combo. I'm going to be upgrading it by replacing the motors and controlling them with VFD's. Space is tight and it occurred to me that if I could use one VFD to control the motors (never at the same time) that would simplify the installation. It would also save money since I would only need one VFD. 
But now the question is how to switch the VFD between the two motors?
My first thought was a 3P2T switch. But I have not been able to find one rated for 230VAC and 1HP. It was suggested to use a contactor. But then I would need a low voltage source for the contactor with a switch for that power source and now it's no longer simplifying things. |
How often do you switch? Perhaps a simple
drop-cord off each motor with a twist-lock
plug could be used to mate the in-service
motor with its power source.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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donjohnston
Joined: 13 Dec 2009
Posts: 231
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| Posted: Sun Feb 14, 2021 2:02 pm Post subject: Re: A 3 phase AC (Alternating Current) question |
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| Quote: | How often do you switch? Perhaps a simple
drop-cord off each motor with a twist-lock
plug could be used to mate the in-service
motor with its power source. |
Unfortunately, often enough that I'd rather not be swapping cables. That's just as bad as having to move the belts to change speeds.
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nuckolls.bob(at)aeroelect
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| Posted: Sun Feb 14, 2021 2:09 pm Post subject: A 3 phase AC (Alternating Current) question |
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At 04:03 PM 2/14/2021, you wrote:
| Quote: | --> AeroElectric-List message posted by: "donjohnston" <don(at)velocity-xl.com>
> How often do you switch? Perhaps a simple
> drop-cord off each motor with a twist-lock
> plug could be used to mate the in-service
> motor with its power source.
Unfortunately, often enough that I'd rather not be swapping cables. That's just as bad as having to move the belts to change speeds. |
Okay, then use a 2PDT switch or relay to switch
two of the three leads between motors. Leave the
3rd wire always connected between VFD and both
motors.
No current can flow to the 'unpowered' motor unless
at least TWO wires are connected. So leaving the
third wire always connected will have no effect
on system operations.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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nuckolls.bob(at)aeroelect
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| Posted: Sun Feb 14, 2021 2:19 pm Post subject: A 3 phase AC (Alternating Current) question |
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At 04:03 PM 2/14/2021, you wrote:
| Quote: | --> AeroElectric-List message posted by: "donjohnston" <don(at)velocity-xl.com>
> How often do you switch? Perhaps a simple
> drop-cord off each motor with a twist-lock
> plug could be used to mate the in-service
> motor with its power source.
Unfortunately, often enough that I'd rather not be swapping cables. That's just as bad as having to move the belts to change speeds. |
Plan C:
Use two of these puppies https://tinyurl.com/y2dya9lc
to effect your 2PDT switching. Only one contactor
energized at a time.
Then you can switch between motors with an itty-bitty
toggle switch located remotely from the high-voltage-fat-
wires.
You'll also need a 24vac source to power the
contactor coils
https://tinyurl.com/yytcqyuy
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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nuckolls.bob(at)aeroelect
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| Posted: Sun Feb 14, 2021 9:52 pm Post subject: A 3 phase AC (Alternating Current) question |
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At 04:08 PM 2/14/2021, you wrote:
| Quote: | --> AeroElectric-List message posted by: "donjohnston" <don(at)velocity-xl.com>
Would I use one leg of the 230v supply to power the coil?
(I haven't used a relay like this before)
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See attached . . .
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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| Description: |
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Download |
| Filename: |
MOTOR_SELECTOR_CKT_FOR_VFD.pdf |
| Filesize: |
30.76 KB |
| Downloaded: |
257 Time(s) |
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