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wiring for a unisaw (3 phase motor, motor starter, phase converter)

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Forum topic by AnthonyHidalgo posted 03-22-2015 04:25 AM 1336 views 0 times favorited 9 replies Add to Favorites Watch
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AnthonyHidalgo

8 posts in 630 days


03-22-2015 04:25 AM

I finally received all the parts to get my recently purchased used unisaw up and running. My plan is to connect from the dryer outlet using SO wire to a phase converter, to the motor starter, to the motor. I’m not sure this is the correct way to wire it, any help would be appreciated.


9 replies so far

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MrUnix

4208 posts in 1660 days


#1 posted 03-22-2015 04:28 AM

What type phase converter? Static, Rotary, VFD?

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

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AnthonyHidalgo

8 posts in 630 days


#2 posted 03-22-2015 04:29 AM

Static

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MrUnix

4208 posts in 1660 days


#3 posted 03-22-2015 04:39 AM

I’ve got the same motor on mine (87-359 3HP 3PH), but using a VFD instead, so I just removed the starter completely as it’s not needed in that configuration. AFAIK, you just treat the SPC the same as you would a 230V 3PH connection. Wire the SPC to the wall outlet, and then wire the motor starter to the SPC just like you would any normal 3 phase connection.

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

View Oughtsix's profile

Oughtsix

42 posts in 635 days


#4 posted 03-22-2015 07:42 AM

If that center picture is a static phase converter you will want to wire like this:
Dryer outlet—> Starter wired for 1ph—? Static phase converter—> saw motor

If you have a rotary phase converter (With an idler motor) you will want to run it like this:
Dryer outlet—> rotary phase converter—> Starter wired for 3ph—> Saw motor

You will start the rotary phase converter first then start the saw motor.

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AnthonyHidalgo

8 posts in 630 days


#5 posted 03-22-2015 08:01 AM

Yes the center picture is the static phase converter. Can you explain why to wire the starter in single phase vs 3 phase from the phase converter? I have an idea but would like to know your reasoning. Thanks

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Oughtsix

42 posts in 635 days


#6 posted 03-22-2015 11:26 AM

A static phase converter energizes a capacitor to start the motor spinning during startup then disengages this capacitor after a set period of time or a set current is reached (depending on the type of static converter). You are really only running your 3ph motor on single phase and the third leg of the motor is only powered for a few seconds while it is starting to turn. The static converter needs to be between the starter and the motor so it can energize the capacitor and third leg of the motor as soon as the static converter is energized then disengage the capacitor and third leg shortly after.

If you had a rotary converter you would start the rotary converter which would generate the third leg of power for 3ph current. You would then use the starter to supply power to the motor in your machine. The motor starter can be a little quirky if you run the coil for the contactor (relay) off a hot leg and the generated leg. The quirkiness will go away of you run the contactor coil off the two hot legs (and not use the generated leg for the coil).

I run 1ph motors off of 3ph starters all the time. You just ignore (don’t use) the third leg. You just have to choose to ignore the leg that is not used to energize the contactor coil in the starter (usually the middle leg). Start by wiring the motor through the 2 outside legs of the starter. If the starter does not energize when you press the start button move one of the hot wires to the middle leg of the contactor. If that doesn’t work move the other hot wire to the middle leg. One of the three arrangements will work.

You will have to change the heaters if you want proper overload protection.

Are there 3 terminals or 5 terminals on the static converter? If three terminals then run the 2 single phase hot legs from the starter to the outside two lugs on static converter then continue running the hot legs to 2 legs of the motor. Run wire from the center terminal of the static converter to the third leg of the motor. There should be a wiring diagram on the static converter… make sure to follow it. All of the static converters I have used use the outside terminals for the hot wires but your static converter could be different.

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AnthonyHidalgo

8 posts in 630 days


#7 posted 03-22-2015 12:08 PM

I will have to try that after I get some sleep. I ended up wiring from the outlet, to the static converter, to the motor starter, to the motor. It seems to start up fine with no load, but I’m not sure if this is bad for any of the components. I only ran it for about 5 seconds to see if it would even turn over.

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MrUnix

4208 posts in 1660 days


#8 posted 03-22-2015 03:26 PM

I freely admit that I have no direct experience with using a SPC, but it sure seems like wiring the starter for single phase and putting the SPC between it and the motor seems rather strange! Anyway, if you wired it up and it ran, that is a good thing :)

Here is a diagram I found (through a search at the OWWM site) that is sort of what I was thinking about:

Again, I am not an expert and have no direct experience with anything other than a VFD, so I will gladly leave the details to the experts!! YMMV!

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

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AnthonyHidalgo

8 posts in 630 days


#9 posted 03-22-2015 07:49 PM

This is definitely how I wired mine up. I’ll check and see how the voltage is on the motor later today.

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