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Clicking, Running in Reverse, and Not Running

Frank R

Stainless
Joined
Dec 18, 2009
Location
Dearborn, Michigan
Just a note: total amateur here; please be patient.

I recently picked up an old Walker-Turner/Rockwell metal cutting bandsaw. The previous owner plugged it in and ran it before I loaded it on my trailer.

I am currently storing it at my brother's pole barn which is 90 minutes away.

The first thing I needed to do was change the 20 amp 3 phase plug to a 30 amp plug which is what my brother has standardized on. He has a 15 HP phase converter built by a local electrician.

I simply pulled out all four wires from the 20 amp plug and inserted them in the same order (in relation to the Ground) in the 30 amp plug. When I started the band saw the motor was turning fine but the magnetic starter was clicking a bit. Not really loud but it was steady. Then I noticed the wheel was running in reverse!

So, I took a moment and downloaded the wiring diagram for the plug (L14-30P 30 Amp 125-250). I figured all I would have to do is reverse two of the legs to get it to turn in the correct direction.

When I wired it according to the diagram, the wheel did not turn at all. I did hear a slight hum coming from the motor though.

Should I remove the magnetic starter and just use the switch?
 
Appears that your bandsaw is depending on two lines that are line generated. But the new wiring makes one of them the generated line from the phase converter.
Just follow the wiring.
 
Appears that your bandsaw is depending on two lines that are line generated. But the new wiring makes one of them the generated line from the phase converter.
Just follow the wiring.

I followed the wiring and it does not run.

I think my next step is to reverse the red and black wires. Not many other options.

Do I need the magnetic starter?
 
One of the wires from the (assumed to be) RPC at the barn is the "manufactured" 3rd wire. That may drop in voltage when the motor is started, and might then have not enough voltage to close the relays. They may click or buzz.

For that, identify the wires from the RPC that are just "passed through", and identify the wires in the saw that are running the relays. Make sure to connect those wires when wiring, so that the "generated" wire is not used to power relays.

If it runs the wrong way then, just reverse the two wires that run the relays, do NOT interchange with the 3rd one.

For a location that has "real" 3 phase, this precaution is not needed.

Are you certain that the motor is set up for the same voltage as the RPC is putting out? (Probably it is, but check)

It could be for either 230 or 460V, and the guy you bought it from might have had it on 460V (might have 460, or use a transformer). Then it would not run on 230V, most likely.

You would need to rewire the motor for 230V, and change the connections on the transformer that provides the control voltage.
 
One of the wires from the (assumed to be) RPC at the barn is the "manufactured" 3rd wire. That may drop in voltage when the motor is started, and might then have not enough voltage to close the relays. They may click or buzz.

For that, identify the wires from the RPC that are just "passed through", and identify the wires in the saw that are running the relays. Make sure to connect those wires when wiring, so that the "generated" wire is not used to power relays.

If it runs the wrong way then, just reverse the two wires that run the relays, do NOT interchange with the 3rd one.

For a location that has "real" 3 phase, this precaution is not needed.

Are you certain that the motor is set up for the same voltage as the RPC is putting out? (Probably it is, but check)

It could be for either 230 or 460V, and the guy you bought it from might have had it on 460V (might have 460, or use a transformer). Then it would not run on 230V, most likely.

You would need to rewire the motor for 230V, and change the connections on the transformer that provides the control voltage.

Thank you for the very clear explanation. I'll check it out this weekend.
 
Webster would rate it as a rhetorical question.
You could also have said "It's one of the services I offer" :)

I will be out there this weekend to take another look. I may have to open up the converter to trace the wires. Can this be checked with a meter instead; just from the plug ends?
 
You could also have said "It's one of the services I offer" :)

I will be out there this weekend to take another look. I may have to open up the converter to trace the wires. Can this be checked with a meter instead; just from the plug ends?

Sort-of. Many of the wires are connected together through the RPC's idler motor, so you would have to find the lowest resistance to identify the ends of one wire. That can be sufficiently unclear, depending on the meter, that disconnecting the wire can be a good deal better approach.
 
Sort-of. Many of the wires are connected together through the RPC's idler motor, so you would have to find the lowest resistance to identify the ends of one wire. That can be sufficiently unclear, depending on the meter, that disconnecting the wire can be a good deal better approach.

It may be different on this RPC.

The guy who built them used a design that I have never seen before. He would remove the armature and, using a lathe, remove most of the mass of windings. Then he would re-install it. He would then use run capacitors to even out the third leg. This allowed him to not use a pony motor or starting capacitors.
 
My experience is that the "generated" leg will have the same voltage or maybe slightly higher voltage than the 2 real legs. The difference is that the generated leg has almost no amperage on it.

On mine I measured the voltage on each leg to ground and ass-u-me the leg with different voltage was the generated leg. It worked well enough to make the contactors pull in on the lathe I had just bought.
 
It may be different on this RPC.

The guy who built them used a design that I have never seen before. He would remove the armature and, using a lathe, remove most of the mass of windings. Then he would re-install it. He would then use run capacitors to even out the third leg. This allowed him to not use a pony motor or starting capacitors.

Described like what Baldor does for Phase-a-Matic motors.
 
It may be different on this RPC.

The guy who built them used a design that I have never seen before. He would remove the armature and, using a lathe, remove most of the mass of windings. Then he would re-install it. He would then use run capacitors to even out the third leg. This allowed him to not use a pony motor or starting capacitors.


I feel VERY certain this refers to thinning the end metal on the "rotor". That increases the resistance, and can decrease start current quite a bit.

Unless more is done, it will generally not mean it starts with no capacitors.............. But, some machining of the rotor iron CAN produce a self-starting motor. There are compromises..... I am not sure that the compromises are good for operation as an idler (removing iron leads to changes in the magnetic field, potentially affecting voltage, and waveform), but I have not looked into it that deeply.

Thinning the rotor metal actually can reduce the efficiency of generation, and increase the "impedance" of the 3rd wire output, leading to a drop in voltage under load.

My RPC has a double set of rotor "windings". A surface layer of thin windings (thin bars), for easy start and low start current, and a deeper layer of heavy "rotor bars", which act once the slip is reduced from start. The latter produce a stronger output on the generated leg.
 
I had a convertor, (4 of them to be exact) built by karam mfg. the had the rotor end machined on a open Lincoln motor for the idler they started easy but would not last long and it would burn a open on the end that was machined. If the rotor stopped in the right place it wouldn’t start and if it did it was noisy. I would weld them back up, ( they were aluminum) and it would last for a while. Replaced 2 different ones, and the new one would fail the same way in time. Weird thing was on the last one that failed whatever you were powering would run backwards. They said it was impossible, couldn’t happen, my electrician verified it was happening and said he has never seen it. Lol. I blame it on taking out the spindle drive on my Mori cnc lathe. Twice!
Fixed the problem by replacing those with a Phoenix panel and 40 hp toshiba motor for a idler. Also built a american system with their panel and a baldor 25 hp idler. Both operate and start flawlessly and are very quiet.


When I find it I don’t need it
When I need it I can’t find it!
 
In a mag starter two of the 3 lines are connected to the coil. It often makes no difference which of the 3 lines L1, L2, L3 are connected to the coil. But for some phase converters the generated "wild" leg L3 won't work when connected to the coil. Trace back and see which two of your three phase lines come from the wall and which comes from the idler motor. It's good to know this anyway. Make sure the two lines that originate at your panel are the ones connected to your mag switch's coil.

And doublecheck to make sure the coil is the right voltage.

metalmagpie
 
It just occurred to me that he hard wired his RPC to several outlets throughout his barn. So I will have to use a meter (with some long leads!) to check which wires are which.

I hope he was consistent in his wiring, as each outlet may have a different wild leg.
 
I seem to remember that he did not remove all of the windings, he just removed the cooling fins on the end. He said this reduced the mass and allowed it to start without a starting capacitor. Also, the constantly charging and discharging running capacitors "evened out" the third leg. My family has three of them by the same guy but none of them get much use.

Going out Friday to check.
 
Are you certain that the motor is set up for the same voltage as the RPC is putting out? (Probably it is, but check)

It could be for either 230 or 460V, and the guy you bought it from might have had it on 460V (might have 460, or use a transformer). Then it would not run on 230V, most likely.

You would need to rewire the motor for 230V, and change the connections on the transformer that provides the control voltage.

JST, I think you guessed well.

Here is the starter:
20211126_155523_HDR.jpg

And here is a close up of the label:
20211126_155531_HDR.jpg

Can I still use this starter with a 220 RPC feed?

Here is the motor and the wiring. I want to do a neater job there. Is switching from 440 to 220 just a matter of using that first diagram on the motor?
20211126_1556041.jpg20211126_155550.jpg
 
If you can get a 230V coil for that one, maybe. It does not appear that you will need to mess with a transformer, since the coil is full voltage.

Re=wiring the motor to 230V, and changing the coil (or the whole contactor) ought to have you going.

BUT, any overload protectors may need to be adjusted, or changed, because the motor current will be higher. It will be listed on the motor tag. I cannot read it in the picture.

The overload is that block attached to the contactor on the left in the picture.

My bet is that you will not find parts for that one to adjust the current, and that you will need to get a new contactor and overload.
 








 
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