Electric motor advice needed
#11
  
I want to put a Marathon brand  3/4 hp bench motor (w/capacitor start) on my bandsaw to upgrade it from 1/2 hp.  I need to reverse the polarity to get it running in the right direction (CW).  It has served fine for 25 years as is. 

I have a regular wall switch on the line to be able to turn it on and off.  This setup has worked fine for the old motor and for the new motor in CCW polarity.

I followed the instructions on the label to switch the red and black wires to make it run CW.  It keeps tripping the breaker on the power strip.  I put it back the old way (CCW) in this setup and it works fine.  Go back to CW and it trips the power strip. Done this twice, same result, except now the power strip is fried, won't reset  (it was at least 40 years old anyway -- it was an "Archer" brand -- Radio Shack?).   So I have reached the limit of my skill and my desire to risk any more shop wiring.  Pause to ask for advice.

What is going on?   (Do I need to change the way the switch is wired as well as the motor?)
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#12
  Re: Electric motor advice needed by DCottrell (I want to put a Mara...)
What is the voltage rating on the nameplate?  Is it 115V, or 115/230V or 115/208-230V?  Or if it's really old, 110/220V?  

It matters, as the wiring connections are different when it's dual-voltage or single-voltage, but reversible.
Tom

“This place smells like that odd combo of flop sweat, hopelessness, aaaand feet.”







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#13
  Re: RE: Electric motor advice needed by TDKPE (What is the voltage ...)
Thanks for replying

It is dual voltage 115/230

The label has a diagram for both voltages.  I used it for years as it came wired, which is for high voltage.  (I used it as a bench buffer)

What is the functional difference between the two?  If I reverse it and wire it for low voltage, will this be sufficient for a 14" bandsaw?  The previous 1/2 hp motor is a simple 115v one.  I am trying to switch it out for two reasons -- because I want to use the 1/2 hp as a grinder (it has 2 arbors) and the 3/4 hp is just sitting doing nothing (only 1 arbor).  Plus it upgrades the hp of the bandsaw.

My shop has regular 120 wiring with 20 amp circuits.   The 3/4 motor worked fine wired hi voltage until I reversed the polarity.

I suppose I could figure out how to put an arbor on the other side, but I don't know how to do that (yet).  I thought this would be simpler!
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#14
  Re: Electric motor advice needed by DCottrell (I want to put a Mara...)
So that motor has 6 (or more) leads in the junction box, not counting incoming mains power?  Does the nameplate say it's reversible, or other wise specify rotation direction?  Got a pic of the nameplate?

Are the leads numbered, or are they identified by color?

If they're numbered, can you report what numbers are connected to what, both to each other, and/or to incoming mains power?
Tom

“This place smells like that odd combo of flop sweat, hopelessness, aaaand feet.”







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#15
  Re: RE: Electric motor advice needed by TDKPE (So that motor has 6 ...)
(04-12-2021, 11:10 AM)TDKPE Wrote: So that motor has 6 (or more) leads in the junction box, not counting incoming mains power?  Does the nameplate say it's reversible, or other wise specify rotation direction?  Got a pic of the nameplate?

Are the leads numbered, or are they identified by color?

If they're numbered, can you report what numbers are connected to what, both to each other, and/or to incoming mains power?
This should help Tom, assuming the motors are the same.   Roly
[Image: 2014-03-15_135036_image.jpg]
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#16
  Re: Electric motor advice needed by DCottrell (I want to put a Mara...)
If the nameplate in Roly's post reflects what yours looks like, then you have Blue-Red-Line 1 (call it black), Orange-Black-White not connected to anything other than each other, and Yellow-Line 2 (call it white), correct?

And you've only switched Red and Black motor leads, for Blue-Black-Line 1, Orange-Red-White, and Yellow-Line 2?  

The Red and Black motor leads, by the way, are the two ends of the start winding.  The motor will run in either direction equally well, but it needs a push to start in whatever direction you want it to run, so by reversing the polarity of that one (start) winding, the rotor will get a push in the desired direction when starting, then it's cut out by the centrifugal switch.

If it runs in the wrong direction well, and has for decades, then the two main windings are correctly connected for the voltage, and only the start winding gets reconnected to reverse rotation.

But I'm confused about the voltage you're actually supplying it with.  See below.
Tom

“This place smells like that odd combo of flop sweat, hopelessness, aaaand feet.”







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#17
  Re: RE: Electric motor advice needed by DCottrell (Thanks for replying ...)
(04-12-2021, 10:06 AM)DCottrell Wrote: Thanks for replying

It is dual voltage 115/230

The label has a diagram for both voltages.  I used it for years as it came wired, which is for high voltage.  (I used it as a bench buffer)

What is the functional difference between the two?  If I reverse it and wire it for low voltage, will this be sufficient for a 14" bandsaw?  The previous 1/2 hp motor is a simple 115v one.  I am trying to switch it out for two reasons -- because I want to use the 1/2 hp as a grinder (it has 2 arbors) and the 3/4 hp is just sitting doing nothing (only 1 arbor).  Plus it upgrades the hp of the bandsaw.

My shop has regular 120 wiring with 20 amp circuits.   The 3/4 motor worked fine wired hi voltage until I reversed the polarity.

Now I'm starting to think you got this motor already connected for 240V service, but you're running it on 120V power.  If it ran a buffer or some other light or non-load, it would start fine at half voltage and probably run fine under load, since the load is very light.

But it's now on a BS and it trips the breaker or power strip when you try to start it?  If so, it's got nothing to do with being configured to run in reverse, and everything to do with running on the wrong voltage with something larger than nothing connected to it.

What is it plugged in to, and what is it actually driving when you start it?
Tom

“This place smells like that odd combo of flop sweat, hopelessness, aaaand feet.”







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#18
  Re: Electric motor advice needed by DCottrell (I want to put a Mara...)
And if that's the case, it should be connected for 120V power.  Blue-Black-Orange-L1 (call it black), Red-White-Yellow-L2 (call it white).  That should both reverse it, and connect for the available voltage.

The motor doesn't care which voltage you use, as long as it's properly configured and the supply wiring is not going to cause low voltage problems, particularly at 120V, since the line current is double that at 240V.  Both main windings will run at 120V in either configuration (with the proper voltage), but it's crucial the leads are connected for the voltage it's running on.  

3/4 hp is not a problem at 120V.  Even 1-1/2 hp is not a problem if the wiring is adequate.
Tom

“This place smells like that odd combo of flop sweat, hopelessness, aaaand feet.”







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#19
  Re: Electric motor advice needed by DCottrell (I want to put a Mara...)
In a few posts you mention that "it trips the power strip". Have you tried plugging directly into an outlet with no power strip? Doesn't seem like that should make a difference--but if the power strip has a surge protector could that create an issue?
earl
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#20
  Re: RE: Electric motor advice needed by TDKPE ([quote='DCottrell' p...)
Yes I am running 120V in the shop.  But I have never changed the voltage choice, just the polarity.

It is not under load when testing.  There is no resistance in the arbor either direction

That diagram isn't quite like mine.

There are 4 screws numbered 1 2 3 4.
   

Low Voltage is   pin 1  Red, orange, line 1  Pin#2,3 not used  Pin #4  Black White, Line 2

Hi Voltage is  Pin 1 Line 1    Pn#2 not used  Pin#3 red, orange, white   Pin #4 black, line2

I have reversed the red and black leads between 3 and 4

I could try setting it up  to run 115 and see if that helps, but I don't know why reversing the polarity would make a certain voltage unsuable, 230 in this case.

The electrical setup of my shop is not ideal. I have one 20 amp circuit which runs all the wall sockets (4) (GFI)   While I never use more than one machine at a time, I regret not making it beefier when I built the shop.


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