# A couple of questions about a lathe motor swap



## luxige (Apr 15, 2020)

I bought an older used German-made lathe, which I’ll post about in detail later. But first, a few quick questions about motor wiring.

The lathe came with a 440/550V motor driven by a 3ph VFD. I’ll be selling those and putting in a nice, nearly new 3hp 220V 1ph Hanning motor I happen to have sitting around. I’ve included a picture of the junction box which unfortunately doesn’t include a wiring diagram. I also can’t find one on the Hanning website. So I’m *guessing* I should connect the Yellow and Blue to one line with Black and Brown to the other line, for (say) Forward. And swap the Blue and Brown connections to get Reverse. So:

Forward = Line1 —> Yel + Blu / Line2 —> Blk + Brn
Reverse = Line1 —> Yel + Brn / Line2 —> Blk + Blu

Question 1: Would it be safe to bench test those configurations, or could I damage the motor if I guessed wrong about the pairs?

The second issue is about the motor control switch. The shop that had this lathe set up a push button panel and disconnected the original switch. For some reason they didn’t discard it, so I still have the control lever and big modular rotary switch. See pictures. The lever has a lock when at center position (all 12 switches open), so that’s “OFF.” Then there are two detents above and two detents below. So I can have Forward/Reverse with and without the coolant pump. (I have a 230V eighth hp motor to replace the 550V one in the pump).

Question 2: Obviously the gear was designed to handle this duty, but is it okay by today’s safety standards? I will add a contactor and E-Stop/Start buttons to shut down line power if needed.

Thanks in advance for your advice.


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## benmychree (Apr 15, 2020)

If you just momentarily "bump" the motor on a bench test, you will not hurt it, and the rotary switch is OK alone, as long as there is a fuse or breaker in line ahead of it, I have a two speed motor on my 19" lathe, and that is how it has been for 40 years without any problem, it uses a rotary two stage set of contacts for both forward and reverse.


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## Alexander McGilton (Apr 15, 2020)

I have some diagrams below that could help. The mechanical system is up to the task though the electrical unit is not necessarily up to the amperage as you are reducing the voltage. So use sufficiently heavy gauge wires that that are to the rated heat, amperage and voltage. 
The Grizzly T24101 is sufficiently large enough for the current and can be used as the safety disconnect and thermal overload. The long yellow line on the right of the grizzly diagram can be spliced then lead to an emergence stop box else where on the machine, continuity when puled out and discontinuity when pressed. Be sure to add a ground line to the Estop box even though is seams useless in adition to gronding the motor, as it will safely trip the breaker if the cable is spliced or filed with water.  The diagram of three circuits is for the drum switch. be sure to get a drum switch of 25 amps.


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## luxige (Apr 15, 2020)

benmychree said:


> If you just momentarily "bump" the motor on a bench test, you will not hurt it, and the rotary switch is OK alone, as long as there is a fuse or breaker in line ahead of it, I have a two speed motor on my 19" lathe, and that is how it has been for 40 years without any problem, it uses a rotary two stage set of contacts for both forward and reverse.



Thank you, Ben!


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## luxige (Apr 15, 2020)

Alexander McGilton said:


> I have some diagrams below that could help. The mechanical system is up to the task though the electrical unit is not necessarily up to the amperage as you are reducing the voltage. So use sufficiently heavy gauge wires that that are to the rated heat, amperage and voltage.
> The Grizzly T24101 is sufficiently large enough for the current and can be used as the safety disconnect and thermal overload. The long yellow line on the right of the grizzly diagram can be spliced then lead to an emergence stop box else where on the machine, continuity when puled out and discontinuity when pressed. Be sure to add a ground line to the Estop box even though is seams useless in adition to gronding the motor, as it will safely trip the breaker if the cable is spliced or filed with water.  The diagram of three circuits is for the drum switch. be sure to get a drum switch of 25 amps.
> View attachment 321125
> 
> ...



Thanks Alexander, that's all very helpful! I have mapped the drum switch contacts and came up with about the same thing, with switching for the pump as well. Good to see some confirmation though. 
That Grizzly unit looks perfect, so I think I'll just go with that. Thanks again.


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## Alexander McGilton (Apr 16, 2020)

Just noticed a mistake in the above circuit. I checked it for short circuit risk but nut for function. The leads to the starter winding weren't staggered enough, see below.


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## markba633csi (Apr 16, 2020)

I wonder if your Hanning motor has an internal capacitor or needs to have an external one provided?- I see 40uF on the nameplate. 
Secondly, the rotary switch should be "rung out" with a continuity tester to verify the internal contact arrangement if you plan to use it
-Mark


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## luxige (Apr 16, 2020)

Alexander McGilton said:


> Just noticed a mistake in the above circuit. I checked it for short circuit risk but nut for function. The leads to the starter winding weren't staggered enough, see below.
> View attachment 321181



Thanks again!


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## kb58 (Apr 16, 2020)

As a separate issue, giving the very high voltage and being 3-phase, it makes me think that the original motor was probably at least 5hp. If so, are you okay with the 80% reduction in potential torque?


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## luxige (Apr 16, 2020)

markba633csi said:


> I wonder if your Hanning motor has an internal capacitor or needs to have an external one provided?- I see 40uF on the nameplate.
> Secondly, the rotary switch should be "rung out" with a continuity tester to verify the internal contact arrangement if you plan to use it
> -Mark



Good points Mark. I'm hoping the cap/s are mounted inside with the centrifugal switch. This was pulled from a multifunction woodworking machine with three of these motors. Worst case: the motors share one set of caps and I'll have to source new ones and figure out how to wire them in.
"Rung out" - always good to learn new lingo! I have done that. I'll be using three of the six modules. I don't think I'll be adding any auxiliary equipment, but I'll leave the other three modules stacked on there just in case.


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## luxige (Apr 16, 2020)

kb58 said:


> As a separate issue, giving the very high voltage and being 3-phase, it makes me think that the original motor was probably at least 5hp. If so, are you okay with the 80% reduction in potential torque?



Yeah, I was surprised that the old motor is only 3 hp, but that's what is on the data plate.


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## luxige (Apr 16, 2020)

luxige said:


> Good points Mark. I'm hoping the cap/s are mounted inside with the centrifugal switch. This was pulled from a multifunction woodworking machine with three of these motors. Worst case: the motors share one set of caps and I'll have to source new ones and figure out how to wire them in.
> "Rung out" - always good to learn new lingo! I have done that. I'll be using three of the six modules. I don't think I'll be adding any auxiliary equipment, but I'll leave the other three modules stacked on there just in case.



Well, it looks like the worst case applies - I'll have to source new capacitors. There are two identical ones, see photo. A momentary start switch kicks in one for the start.
I haven't been able to find the exact part number. How close do the specs need to be?


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## luxige (Apr 16, 2020)

Would one of these work?

(Second photo is AV ARCOTRONICS 40uF +-5% 1.27.6NAH MKP 420V 470V Capacitor)


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## Alexander McGilton (Apr 16, 2020)

You have to be careful about using Start or Run capacitors. Start capacitors are designed for only short duty as they can burst if run too long. They are for a given capacitance; cheap, light and compact. Where as Run capacitors are more resilient capable of running continuously. You can use exclusively run capacitors knowing that they are bulky, expensive, and heavier. You may well use them for safety.


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## luxige (Apr 16, 2020)

Alexander McGilton said:


> You have to be careful about using Start or Run capacitors. Start capacitors are designed for only short duty as they can burst if run too long. They are for a given capacitance; cheap, light and compact. Where as Run capacitors are more resilient capable of running continuously. You can use exclusively run capacitors knowing that they are bulky, expensive, and heavier. You may well use them for safety.



Ok, once again very helpful! I vaguely remember reading about that, definitely needed the reminder...
How can I tell if it’s rated for Run duty?
The one in the picture on the left (post #13) is specified as a Run cap in the auction listing. I would guess that fits with the “-R” after the part number. The other two auction listings don’t specifically say Run or Start.

BTW, all of these are the same capacitance as the stock part, but the voltage specs are all a bit off of the specified 400V. Is that a spec I need to match?


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## Alexander McGilton (Apr 16, 2020)

It should be fine using a 440v in the place of a 400v.

 "They Come in a Variety of Sizes and you will need to know your Microfareds or uF also the voltage however you can use a 440Volt in place of a 370Volt but not a 370 in place of a 440Volt. The Microfareds must stay the same within 5% of it's original value. "




__





						Round Dual Run Capacitors  :: Run Capacitors  :: Air Conditioner Parts  :: Just The Right Air . com
					

Round Dual Run Capacitors,used in starting the compressor and condenser fan motor at the same time



					web.archive.org


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## luxige (Apr 16, 2020)

Alexander McGilton said:


> It should be fine using a 440v in the place of a 400v.
> 
> "They Come in a Variety of Sizes and you will need to know your Microfareds or uF also the voltage however you can use a 440Volt in place of a 370Volt but not a 370 in place of a 440Volt. The Microfareds must stay the same within 5% of it's original value. "
> 
> ...



Thanks. I ordered two of the CBB65-R. Turns out the R means “round.”
Now I’m thinking about adding a centrifugal switch to cut out the start cap. The other machine uses a momentary switch to start, and I’d rather just use the shift lever without also having to push a start button. Thoughts?


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## Alexander McGilton (Apr 17, 2020)

Did it not already come with a centrifugal switch? Since the starting coil only runs momentary some manufactures use this as a means to get away with smaller gauge wires than are capable of running continuously. How was the motor original configured?


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## luxige (Apr 17, 2020)

No centrifugal switch, it was set up like a typical woodworking machine. To start, you turn a spring-loaded switch which closes the contactor and also energizes the start cap. When the motor comes up, you release the switch and it springs back to n/o. So the operator is taking the place of a centrifugal switch to cut out the start cap, while the contactor keeps its own coil energized until you hit one of the several stop buttons.

I can't pull all this stuff from the machine and transplant it as-is because I need it to run the other two motors. It's in storage and I only had a few minutes yesterday to pop in and discover the pair of capacitors that are shared by the three motors. I'll make time today or tomorrow to dig in and trace all the wiring so I can just duplicate it. (If anyone's interested, it's a Robland X31 and I'm removing the shaper spindle, keeping the saw and jointer/planer).

It looks like there is no room inside the motor housing to squeeze in a centrifugal switch, so it would have to be mounted outboard. I'll have to wait until I get the gearbox installed to see if that could work.


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## markba633csi (Apr 17, 2020)

The cap you ordered should work fine
"ringing out" is a term from even before my time; it refers to testing a motor or generator armature on a fixture that buzzes when there is a shorted
segment on the commutator- I think


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## luxige (Apr 17, 2020)

markba633csi said:


> The cap you ordered should work fine
> "ringing out" is a term from even before my time; it refers to testing a motor or generator armature on a fixture that buzzes when there is a shorted
> segment on the commutator- I think



Thanks for the input!


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## luxige (Apr 17, 2020)

One more new wrinkle...
I found the user manual for the woodworking machine, which I didn't even know I had. It has wiring diagrams, unfortunately they are only a little bit like reality. But they do show 100k resistors in parallel with the capacitors. I removed the end cover from one of the capacitors and there's the resistor. See photo. Bands look like tan, brown, yellow. Which makes no sense. Then I realized maybe they faded from brown, black, yellow = 100k. They are about 9mm long and 3.2mm diameter, which would be .5W. Ordered some.

In related news, I have mapped the wiring of the contactor/overload, selector switch, start & stop switches, and capacitors as installed in the original machine. My head hurts now.


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## Alexander McGilton (Apr 18, 2020)

That is a bleed resistor, it takes a little bit of power away from the motor when running, though it makes the whole thing safe for when being serviced. It bleeds off the capacitor's energy hopefully before you get your hands in there. Just a quick calculation, if there is 400volts across that capacitor, then there is 1.6 watts needing to be dissipated for the first moment. That of course quickly drops off so over a the dissipation duration, the engineers probably said that a half watt was good enough not to over heat. Though that concerns me that they were sparing with cost that they couldn't put a 2w resistor in there.


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## luxige (Apr 18, 2020)

Thanks for the expanation. I'm learning as I go, and all this helps.
To clarify, the machine this motor is coming from is 220V. So 0.5W seems correct, yes?


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## markba633csi (Apr 18, 2020)

Yes but this is ac so there are peaks that are higher-220 is the RMS or average value of the voltage
100 k was chosen so the cap would bleed off fast- you could put a higher value in there like 500k and just wait a few seconds longer before servicing the caps
Most motors don't have a bleed resistor but it is a good idea
-m


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## luxige (Apr 18, 2020)

Thank you!


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## luxige (Apr 25, 2020)

Success! The motor runs and reverses. The big rotary switch controls the direction and also runs the coolant pump when moved to the high speed position. (The original 440V setup had two speeds in each direction). My new motor only runs at one speed so I'm using the extra switch positions to control the coolant pump. I replaced the 550V 3ph stock pump motor with a 230V 1ph 1/8 hp motor I happened to have laying around. I added an old Start/Stop switch and E-stop switch to control a contactor and overload cutout similar to the one recommended in post #3.
Everything is working, however.…



luxige said:


> Now I’m thinking about adding a centrifugal switch to cut out the start cap. The other machine uses a momentary switch to start, and I’d rather just use the shift lever without also having to push a start button.



An odd thing: it seems I won't need to worry about that centrifugal switch. (When the control lever is in neutral, all motor and capacitor leads are isolated. Moving it to a run position energizes the appropriate motor leads and the Run cap. The Start cap can only be connected by pressing the Start button, as this is the only way I could figure out how to keep it from always being on without a centrifugal switch to cut it out.)
So I was expecting to have to hit the Start button each time I moved the control lever to a new position. 
But! The motor starts anyway, as soon as the control lever is set. ??? My first thought was that I had wired the Start cap wrong and it was always getting power. I triple checked my plan and also tested for continuity between power leads and cap leads. No mistake, that motor is starting without the Start cap.

So.… any problem starting the motor that way? I don't want to do damage just because it's convenient.


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