Wiring drum switch to reverse single phase motor

jeff260z · Oct 9, 2008

Hi all

I bought a Standard Modern 1340 lathe that was wired 3 ph. It was missing the drum switch and motor so I bought a rebuilt 3HP single phase reversible 240 volt motor. I also bought a square D drum switch of ebay of cheap.

Here is my info...

Thanks

Jeffrey

2Slow · Oct 9, 2008

The below should work. I am using the numbers from your attached images:

Connect Terminal 1 of your drum switch to wire #5 of your motor

Connect Terminal 2 of your drum switch to L2 and wire #4 of your motor

Connect Terminal 3 of your drum switch to wires # 2 and #3 of your motor

Connect Terminal 4 of your drum switch to wire #8 of your motor

Connect terminal 5 of your drum switch to wire #1 of your motor

Connect Terminal 6 of your drum switch to L1

That should work, but it always leaves L2 connected to wire #4 which is not the best idea, but I did not see a way around that.

This thread, and this thread, may be helpful.

-Joe

TheMutsNutz · Oct 9, 2008

I assume you're asking how to connect the motor. If so:
Motor ........ Switch Pin
4+L2 ........ 1
8 ........ 2
5 ........ 3
2+3 ........ 4
L1 ........ 5
1 ........ 6

I assume you have some isolator or power switch as othewise motor #4 is permanently connected. Ok-ish if it's neutral, but not too cleaver if it's really a line.

Cheers Richard

jeff260z · Oct 9, 2008

Hi guys, was working on this while you posted. Yes I do have an overload and contactor with start stop buttons. This drum switch doesn't have a normally closed interlock for the off or center position to interlock my motor starter. I shouldn't need it should I?

Would this work?

jeff260z · Oct 9, 2008

Here is the original lathe wiring diagram. Thanks for the help guys.

2Slow · Oct 9, 2008

The schematic I posted, the one TheMutsNutz posted, and the one Jeff posted will all work. All of them leave L2 hooked up to the motor, but since you have a contactor ahead of it that should be fine.

-Joe

ggg · Oct 29, 2008

I have the same issue

I have a Century Electric Motor (Wiring diagram C32536) with colored wires not numbers. I basically have to have the "Brown Wire" (the number 4 wire in the above diagram) always connected to one of the line wires.

There doesn't appear to be any way around it.

I have a Cutler Hammer drum switch That does not have a diagram available either. it is a 9441 H258C

I do not have anything between the switch and the power outlet. So #4 wire has power to it always.
Do I have to unplug the machine when not in use? What is the #4 wire? The wire diagram for the South bend 10" in another post also shows a lead always connected to power. so is it OK?

Thanks
Glen

diesel-xj · Jun 24, 2019

reviving the dead here a bit. I also have a standard modern 1340 lathe. It only went under salt water for a little while in Hurricane Harvey. The budget on the shop repair is very tight. I am replacing the 3hp 3phase motor and VFD with a 5hp 220 single phase motor. Now my drum switch is too small, and also not in very good shape after its gulf of mexico bath.
I am looking at some of these cheap 60 amp drum switches If I understand they are 6 terminal 4 straight 2 cross 3 positions switches. They are advertised to work for single or 3 phase power. If I understand this switch will work, but I will have to leave one leg of the motor hot all the time? is that correct? Below is a link to the drum switch and a pic of the circuit

Drum Switch Forward/Off/Reverse Motor Control RainProof 60A Reversing Guaranteed 662425078356 | eBay

My new to me 5hp motor has 4 wires. and the wiring is shown below. Is it even remotely ok to leave a hot leg on the motor??? that does not seem rite?

If anyone has a line or link to a single phase 5hp 30amp drum switch I am interested. the other option is to put the new to me 5hp motor back on the compressor that I bought it with; and sell the whole working compressor and see if those funds will cover a new used 3hp 3phase motor and a cheaper VFD. I lost a USA made Lenze VFD in the storm, and the Lenze's are a bit pricey now, I can get a china VFD for less than half the cost of the Lenze

thanks

9100 · Jun 24, 2019

This issue keeps coming up and I keep posting the same response. Drum switches are dangerous on normal single phase motors because the direction is determined when the motor is stopped and the starting winding is connected. After the motor reaches a reasonable speed, the starting winding is disconnected by a centrifugal switch. In a panic situation, if you slap the switch all the way over to reverse, the motor keeps going in the same direction, rolling your sleeve up or whatever bad it is doing. A three phase motor will reverse, unrolling or at least giving a moment to stop it. If you use a drum switch, it should be only used for presetting the speed and something like buttons should be used with a big red stop button.

I refuse to run a single phase lathe with a drum switch.

Bill

diesel-xj · Jun 25, 2019

ok enough said. I think it will be easier to just bite the bullet again and go back to 3phase with a little china VFD.
But I still have a few questions. Is there actually a dedicated single phase reversing drum switch? I have seen 2 different switch diagrams, one that indicates single phase and has ( for lack of a better word) a double dog leg set up. Then the 3phase set up which have 2 straight and one cross terminal.
And that you can use the 3phase style drum switch to get the job done in single phase, but it is not ideal because it requires that one leg on the motor stays hot all the time? and the as mentioned problem with the motor not actually reversing in a quick switch situation.

Next do some 3phase motors use a centrifugal switch? I thought not. The fellow that sold me the single phase motor has a 3ph motor that looks like it will work, but it has a what looks like a reset button on the back like I see on single phase compressor motors. The motor is 200 miles away, so all I have is pictures.

and lastly. Does anyone have a ball park figure for what is should cost to have a saltwater flooded motor repaired. most all my motors actually work, but they have lots of bearing noise. My local (40 miles away) motor shop will not give me even a ball park cost without a teardown and I have had one person tell me he thought it would be cheaper to replace than rebuild.

thanks

Bill Simmons · Jun 25, 2019

Diesel,

Why send those motors to a shop. The three phase motors are quite simple. Disassemble, flush with lots of fresh water, replace the bearings which are available everywhere (including Amazon), bake the motor to remove moisture and reassemble.
Megger the windings after baking and if there is no leakage to the case, you are good to go.

jim rozen · Jun 25, 2019

" you can use the 3phase style drum switch to get the job done in single phase, but it is not ideal because it requires that one leg on the motor stays hot all the time? "

There is an elegant way to accomplish reversing for a 240 volt motor (of the dual voltage type, that is a 120/240 motor
wired up for 240 service). It does involve going into the motor and bringing out wires that might not otherwise be
accessible.

But it provides reversing service, a bare minimum of conductors between the switch and the motor, and best yet does not leave any wires
hot in the motor, when in the off position. If there is interest I will post up the wiring diagram for that.

As far as single phase motors being (hardly ever) instant reverse, well yep. I make it a point not to do unsmart things with my machine tools,
to the point where I always placard them with a sign that says "DO NOT DO DUMB SHIT WITH THIS TOOL."

So far it's working out.....

diesel-xj · Jun 25, 2019

Thanks for the encouragement Bill, I will get a report from the motor shop tomorrow. I have no idea what they will say. I did think to try a do a bearing replacement myself. My shop is just barely coming back. My press is still not working I need a O-ring kit to rebuild both the pump and the ram. If the motor shop can rebuild it for less than the $125 I can get the replacement for I will think about it. The other little 110vac motor I took the shop I think I can get a used motor for about $50-75, I don't think I can mess with it for that. I think it will need bearings and a centrifugal switch. I doubt I can find the parts for less than I can replace it for.

Jim I am interested in the schematic just too see it. My 5hp single phase motor is single voltage type as far as I know. it only has 4 wires. But I am still interested to see what you are proposing.

thanks

9100 · Jun 25, 2019

Re washing motors, after the '93 flood I cleaned a couple of generators that had gone under. Not salt water, but fairly noxious. I put them in a vacuum chamber submerged in water and alternately pulled a vacuum and let it back to atmospheric pressure. The idea was to force water into every pore and then boil it out by lowering the pressure until the water boiled. Then I dried them out in an oven a little above 212 F. All I can say is that it worked. Whether it was needed, I can't say.

There was one unwanted effect. The moisture made the fiber vanes in my vacuum pump swell and bind and it was months before it dried out enough to run normally.

Bill

DDoug · Jun 26, 2019

9100 said:
Re washing motors, after the '93 flood I cleaned a couple of generators that had gone under. Not salt water, but fairly noxious. I put them in a vacuum chamber submerged in water and alternately pulled a vacuum and let it back to atmospheric pressure. The idea was to force water into every pore and then boil it out by lowering the pressure until the water boiled. Then I dried them out in an oven a little above 212 F. All I can say is that it worked. Whether it was needed, I can't say.

There was one unwanted effect. The moisture made the fiber vanes in my vacuum pump swell and bind and it was months before it dried out enough to run normally.

Bill

Very interesting take on cleaning there.

A "Water VPI".

Makes sense, in that you chased out the bad water (and in the OP's case, salt water)
with a known clean fluid. So you had a much better starting point for the drying out
process.
I wonder if using DI water would be better yet ?

9100 · Jun 26, 2019

digger doug said:
I wonder if using DI water would be better yet ?

Couldn't hurt.

Bill

jim rozen · Jun 26, 2019

As promised, a handy way to wire up a reversing drum switch for a 12/240 motor when wired
for 240. The two run windings are in series for the higher voltage. The start winding is 120 only
so one end of that goes to the centertap between the run windings.

In principle you only need three conductors plus a ground between the switch and the
motor. In the diamgram below, there are two more so a thermal overload can be
wired in there.

Depending on which hot leg it is tied to, the motor will go fwd or reverse:

diesel-xj · Jun 26, 2019

thanks for the schematic. I will have to keep that for later.
I did evacuate ( run from the storm ) with one good vacuum pump. But my vacuum oven went under water. I guess the vacuum chamber of the oven will still be good. But the oven has been sitting outside since one of the first muck outs. I think the gasket will be no good. I do remember that gasket is over $125.00 for a piece of silicone, if you can find them now. Again probably cheaper to get a used vac oven than repair the old one. I threw out maybe 5 good duo seal oil vacuum pumps after the storm. I used to sell them.
Well no point dwelling on the losses. I thought to put the 3hp 3phase motor in a bath, to de salt it. I really wanted to do a full submerge in the Evaoprust (chelation chemical rust remover ) first, and then do a water bath. But someone on one of my other threads on here really thought that would be a bad idea. I still might try it . I just got off the phone with the motor repair, They condemned the little motor, I will guess that they will condemn the 3hp as well. I just hope she doesn't destroy them in the check out process. I guess I should have known better than to send them out.

thanks for the schematic and info

Reginaldian · Apr 22, 2020

I have a S M 1340 with an Allen Bradley drum switch. Can someone help me with a wiring diagram to convert it to a 3hp single phase motor

Froneck · Apr 22, 2020

Is there more than one connection here? Jeff26Oz does not have to worry about double pole 240VAC disconnect with the drum switch. He has a 3 phase contactor to wire in so that he can disconnect both sides of the line. There is probably a better diagram for the connections so that if the drum switch is flipped to reverse the selected operation will drop out the contactor rather than try to reverse the motor as 9100 mentioned is dangerous because a single phase motor will not reverse until RPM falls below Centrifugal switch re-connection speed. It will then coast to a stop which is better than continuing at the same speed. Since Jeff26Oz did have a reversing 3 phase motor that came with the lathe it probably don't have a threaded spindle which is not intended to run in reverse! So anyone else having a threaded spindle should not reverse motor direction.
Anyone else than Jeff26Oz should open another topic so the thread can keep apples with apples and not add peaches pears or bananas not me mention oranges! When asking connection help Include motor and switch wiring diagram of what you have.
Also be careful with standard drum switch wiring diagrams. Not all motors are wired the same, Jeff26Oz's diagram shows an interchange with the "center connection for 240VAC and #4 L2 for the start winding wires 5 and 8 but other motors ate not so obvious so wiring investigation might be required or the motor can be damaged!

Wiring drum switch to reverse single phase motor

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