# 1/2 HP single phase



## greghaa (May 18, 2012)

I have a lathe I have rebuilt.  Well almost but its time to start thinking wiring.

It has a 1/2 HP single phase motor with a capacitor on it and 4 leads.  2 green and 2 red.

The docs about the wiring aren't exactly clear and I was wondering if anyone knows of any
basic documentation about wiring a motor like this.

The only thing it powers is the lathe spindle but it is meant to have forward and reverse.
Do I just reverse the direction of the AC through the windings?  Like wire the second 2
wire backwards from the first?

I feel like I am missing something...

Also, I want to use new wire and the leads from the motor only have a few inches left coming out of the housing.
Can I just run new 18 gauge solid core?  Do I solder it?  What type of connection is good to splice to the motor
leads?

Should I get the motor fixed with proper leads coming out of it?  Am I gonna burn my house down?

I have done a lot with electronics, but not much with motors or HV AC.  Mostly low voltage DC stuff.

Thanks!!

-greg


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## Hawkeye (May 18, 2012)

Okay, Greg, I'm going to wing it. I'll assume you have a DMM, since you have experience in electronics. Start by shorting the wire pairs to make sure the capacitor is drained. If you connect the meter, set to ohms, across each pair of wires, you should find one pair that reads a steady low resistance and one that acts like a capacitor charging (low ohms to begin and steadily increasing resistance). An analog meter will display this better. Mark the capacitor pair "Start" and the steady pair "Run".

The Run winding is connected to power through a switch (ideally part of the Fwd/Off/Rev switch). The Start winding is connected through the reversing portion of the switch. You could use a 3PDT, centre-off switch (rated for the stated _inductive_ current) and add the appropriate jumpers.

As you surmised, the motor is reversed by swapping the connections to _one_ of the windings. That should be the Start winding that is swapped to reverse.

I wouldn't use #18 solid in a motor - too easy for it to break from the vibration. I'd use stranded and probably #16 for a small motor. My preferred method to extend that type of wiring is to solder the wires as "J-hooks" and heat-shrink them.

Hope this helps. Others will undoubtedly add to this.


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## greghaa (May 19, 2012)

hey

So I do see the low ohms to begin and then it increases on one pair, but the other pair has infinite resistance (green).

I looked inside and the green pair goes to the cap.  My DMM can test capacitance and the cap in there is
120V 300uF.  When I test the green pair for R, I get infinity. Seems right.  When I test for capacitance I get nothing really
and certainly not the 300uF I would expect.  I tested a 1uF 370V AC cap I have and got the correct reading with my meter.
So is my cap bad?  Or my meter cannot test to 300uF. I need to check what limits exist in the manual.

I will try to hook it up with green as cap (start) and red as run and see what I get.  I will just do it on the bench first 
with a switch before I wire everything up.  If the cap is bad then there is a good electric motor shop up the road from me.
I am sure they have something.  Either a new cap or a used motor.  The place is giant.

Thanks for your help.

-greg


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## Hawkeye (May 19, 2012)

If you're getting infinite resistance, the coil is either separated from the wires or broken somewhere (burned out). Did you try reading between reds and greens? Most likely they are connected in colour pairs, but you never know.

It seems odd that the reds read like a capacitor. If the greens are connected to the cap, the reds should read steady low resistance. The capacitor pair may not read as increasing resistance because a digital meter with FET inputs may not put out enough current to charge a large cap very fast. Again, an analog meter will show the process better.

If you're game, try connecting one red, one green to black; other red and other green to white. Run it through a switch so you can shut it off quickly. Worst case, it pops a breaker. Best case, it runs. Take note of the direction, then swap the two green wires and try again. See if it reverses. Tag all wires and you're good to go.


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## Tony Wells (May 19, 2012)

A motor with two leads for power cannot be reversed as simply as swapping the AC power. That works for DC only. AC motors are reversed by changing the arrangement of the coils in the field by swapping the separate winding connections. Reversible motors will have more than 2 leads to the field. 

Is there a nameplate with a model number on the motor? Or perhaps a picture?


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## greghaa (May 19, 2012)

Attached are photos of the plate and the leads.  Motor still needs a bit of cleaning...

It is from this

http://www.northerntool.com/shop/tools/NTEUnpublishedItem?storeId=6970&langId=-1&rfno=7171

but seems many of these combos are the same with the same motors.

Also, I did at one point put the greens and reds together, ran them to black and white thru a switch and the motor ran fine.
Never reversed them though...  Will try that.


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## greghaa (May 20, 2012)

Hi 

So that is working fine.  Green/red to black and green-red to white.  First time it had the motor spin clockwise or if attached to lathe 
the chuck would spin towards me.  Would that be considered forward or reverse?  I am thinking that's reverse but I am not sure.

Thanks

-greg


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## Tony Wells (May 20, 2012)

That is forward. Top of the chuck towards you, or CCW as viewed from the tailstock.


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## greghaa (May 20, 2012)

Ok.  Thanks!  That makes sense now that I think about it more.

My only other questions is about a switch.  I will need a 3 position 2 deck switch?

To switch the greens and keep the reds the same I sould need 4 poles on the switch?
Does that sound right?  Trying to envision it and the seems right to me but I guess 
it might take more than 4?  I tried with a 3 position 3 pole switch with the reds together
and I got nothing.  

Any ideas?

Thanks

--


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## Hawkeye (May 20, 2012)

If you use a 3PDT, centre-off switch, you only need one switch. You connect the black supply wire to both outside terminals and the red from the black connection to the centre terminal of the first set of terminals. That way, power is applied to the red wires when the switch is moved either way from the centre-off position. Use your ohmmeter to get the three rows of terminals straight in your mind.

The rest of the switch is connected the same as if you were connecting a DC motor for reverse operation.



Instead of + and -, write in black and white for the left wires and green-from-black and green-from-white for the right wires in the drawing, relating to the way you got it connected in your test setup. The black wire on the left should come from the same terminal that you used for the first red wire, so that it is off when the switch is off. The crossed lines at the centre of the switch drawing are insulated jumper wires you will need to add.

The white wire from the power cord connects to the other red wire from the motor and to the appropriate (-) centre terminal of the reversing part of the switch.

If you prefer, you can use two switches - a DPDT switch, used as outlined above, and a SPST switch to turn the power on and off as in the first description. The difference is that you run the risk of turning the lathe on, realizing that you wanted it to reverse, and reversing it while it is running. You really don't want to do that. :yikes:

When shopping for a switch, make sure you get one that is rated for over 125VAC and more than the inductive current shown on your motor label.


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## greghaa (May 20, 2012)

I figured I needed a switch that can run red no matter what.  Like it can connect multiple connections at once.

I found this one (hope I am not breaking the rules posting this, sorry...)

http://littlemachineshop.com/products/product_view.php?ProductID=3378&category=

I am gonna check the local Fry's, they have stuff like that a lot of the time.  Maybe save 
a few bucks in the process...

Thanks everyone for the help.  I do appreciate it.

--


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## greghaa (May 21, 2012)

All

I am running a 10 Amp fuse inline on the black (hot) connection from the wall.

It keeps burning the fuse on spin up of the motor.  Should I be using a slow blow fuse or something like that?

What do others use?

Thanks

-greg


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## Hawkeye (May 21, 2012)

Generally, the 15 amp breaker that feeds the wall outlet should be sufficient protection. You only need to add smaller fuses if the device you're powering would be damaged by more than 15 amps AC.


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## greghaa (May 21, 2012)

Then I am reading the manual wrong.  It states 

"A 10A fuse should be fixed in front of the supply socket to maintain short circuit protection."

The supply socket must be something else. I am not understanding what they are referring to.
I figured this was the supply socket from the wall?  

Unless it has something to do with the other motor that turns the drill/mill head.  I don't have that
done yet and am only dealing with the lathe.  

ok.

Thanks

-greg


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## Hawkeye (May 21, 2012)

Bear in mind that the motor was made in China for a wide market. Not all countries have the same regulations for house wiring that we take for granted. They just want to make sure there is some protection. The translated term "in front of" would normally be "before" here - on the supply side of the duplex receptacle (yes, that's what it's really called).


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## swatson144 (May 22, 2012)

If the lathe has a threaded on chuck/spindle I'm not so sure I'd get overly concerned with reverse. I'm always a little concerned I'll unscrew the chuck running in reverse. That is a whole bunch of excitement I don't need. Only times I have used reverse is to back out a tap etc and that is just feathering the clutch. I could happily do without. When the drum switch goes out on mine unless I can find one cheap I'll probably just do it up 1 way with an emergency stop.

No more than I single point metric threads I can do without reverse even for that. Just switch out of back gear and turn the chuck. I usually end up hand turning to get to the end point anyway so I'll already be out of BG. It is a little handy to start reverse and slip the clutch but I could do without the couple times a year I need a thread I don't have a die for.

Make sure your switch has a mechanical interlock, so you can't go past the off position without meaning to. You don't want something to go wrong and you slap the machine  from FWD to REV while it is running with the clutch engaged. Ungood! and with a threaded chuck a good way to drop it. There are also machine switches with separate interlocked buttons for FWD, stop, REV.  

Steve


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## greghaa (May 22, 2012)

It does have a threaded chuck, but it also has 2 bolts that tighten down to hold it in place.  Probably for the reasons you specify.

You are probably right as this is my first machine and one I am learning on.  So I doubt I will be using reverse much if at all...

I guess going thru the rebuilding process I am just trying to get it back to stock and where it was originally.

Threading isn't something I have thought much about and that will probably be difficult on this machine.  I don't think it has
any type of auto-feed or anything like that.  Although I have thought about turning it into a CNC machine that would 
likely be a wasted effort and not something I am prepared to do for a long time.  I need to understand how to run the machine
manually before I go trying to automate anything.  

Thanks for the help you guys!

-greg


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## Hawkeye (May 23, 2012)

Actually, with a single-phase motor running at speed, the only thing that will happen if you skip through 'Off' and put the switch into reverse is that it will continue to run in the same direction. The direction is initially set by the start winding, but only until the motor is going fast enough to open the centrifugal switch. The 'Run' windings are always connected to the same 'polarity'.


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## swatson144 (May 23, 2012)

That is correct but it still doesn't stop. 

I hadn't really thought of it, though I've wired several motors and should know it wouldn't go into reverse without restarting.

Thanks for pointing that out.

Steve


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