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Allen Bradley size 0 mag starter for lathe

diesel-xj

Aluminum
Joined
Sep 27, 2011
Location
South Texas
Good evening everyone. first time poster here. I have a new to me Standard Modern 1340 lathe. the lathe is 3hp 220volt 3 phase with a built in brake. The machine also had a pneumatic chuck that was missing some piesces, So I removed the pneumatic chuck. I guess that is where I messed up. I did not take pictures of the wiring first. Well long story short, All the smoke leaked out of the Allen Bradley 70A86 coil in the mag starter. So I did some research on this forum, and thought the problem was that the coil was on the manufactured leg from my phase converter, so I got 3 new coils, for cheap, and changed the wires around so the coil had house 220 coming to it. Well the same thing happened, That darned smoke leaked out again.
My phone a friend electrician, pointed out that I needed to check the voltage of the coil. Well that was a light bulb moment, sure enough, the 70A86, is a 120vac coil. So to make this even shorter. I would like a part # for a 220VAC Allen Bradley coil.. Would a 70A83 work? also I saw a 72A06?
As part of the Chuck removal, we removed a transformer. I guess the transformer was wired in to the chuck and then the starter coil as a safety or something. Well I don't know how to wire the transformer back up, my phone a friend electrician suggested I just get a 220 coil, and be done with it.
I am running a homebuilt rotary phase converter, I had to get a bigger motor from the unit running the mill. So this is a new rotary converter from a 5hp motor. I checked the voltage at the lathe mag starter, on the L1,2,3
L1-2=238volts.
L1-3=212 volts
L2-3 = 207 volts.

That part is interesting to me. I sure am having fun trying to figure this out. I have learned a lot so far, look forward to learning even more.

thanks for any advice.
 
Try another 120v coil

... so I got 3 new coils...

Funny coincidence - I just built an RPC, this month, using a 5 hp idler and and an Allen Bradley starter with a 120v coil, for my TurnPro 13-40 lathe with a 3 hp motor & foot brake.

I attached a schematic of my wiring.

Note that the on/off switch uses 120 volts L1 to neutral. I didn't include a symbol for the coil, but the on/off switch is controlling current through the coil.

I can't think of any reason you can't do the same with one of your remaining 120v coils - good luck!

Bill Pidgeon
 

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thanks for the replies. I went ahead and purchased a used 220vac coil. The machine works. But. The starter has a pretty loud buzz/hum, when energized, and now after the machine has run for a few minutes, it trips out one of the 3 reset overloads? Always the same leg trips. I beleive it is on part of the manufactured leg from the phase converter. Are there any ways to bring the manufacutered leg voltage up to 240v. is there a small transformer that can be used?

thanks
 
"Well that was a light bulb moment, sure enough, the 70A86, is a 120vac coil."

It is somewhat common to find 120 VAC coils on machine made for 230 or even 460 volts.

Such machines usually incorporate a small control transformer to "derive" 120 volts from the incoming line voltage, and such control transformers often have a 230/460 primary and a 120 secondary.

In this way, the machines need only L1 and L2 (or L1, L2 and L3, for three-phase), and the neutral is not needed at all.

Also ...

Certain machines have a low-voltage control option, where the coil and the controls are 24 VAC, yet the line voltage can be 230 or 460 volts or even 600 volts.

In this case, the control transformer has a 230/460 (or 600) primary and a 24 volt secondary.

In the old days, before OSHA, many machines used line voltage controls, whereby a machine sold for 230 would have a 230 volt coil and a machine sold for 460 would have a 460 volt coil.

This led to some interesting problems where the same internal pathway, often a length of 1/2" EMT, would have several classes of voltage running next to each other.

One machine in particular used the very same 1/2" EMT for 460 for the starter's coil, 120 for the work light accessory and extra-low voltage for the drive system's speed control potentiometer, and all of these were "fixture wires", none of which was rated for more than 125 volts. An accident waiting to happen, obviously.
 
An accident waiting to happen, obviously.

yup
thats why as often as possible i flush the old wiring and start from scratch
a bunch of old brittle mixed up crap in my machines ain't what I'm talkin' bout.
half the time it's been monkeyed with by a..a... well lets just say by monkeys
some nice fresh MTW front to back with some clean and tidy starters just gets things off on the right foot.


the voltages you describe arn't all that refined but it ain't much out of +/- 10 %
i would wish that that would not trip a good motor/heater

i suspect there is something a miss

for one thing, if that contactor is not holding in tight it may be creating a high resistance connection right there

another is if you changed the motor wiring from high to low voltage to accommodate you rpc the old heaters are not the right size anymore and will not hold
 
Nope I did not change the voltage on the motor. All I did was pull off the old pneumatic chuck, and all of its wiring and plumbing. I think you gave good advice though. I will try and clean the contactor some more. i cleaned it a bit already, but it is still pretty dirty from smoking the 2 coils recently. I was a bit concerned that there was a coating on the steel laminated magnet halves, but I don't think there is? One of the halves comes out easy. the other half I will have to take the whole upper part of the contact apart.
looking back at this, i probably would have been better off getting a VFD. But I am completely ignorant about them, so that was a bit scary, plus I thought they would be more expensive. I have now seen single to 3 phase 220 volt VFD for a 3 hp motor for $175 to $250. If I had known that, I probably would have gone that route. All in all I think I am into the new 5hp RPC for about $165, so that is not too bad, and I still have spare coils. With a VFD do you have the choice to keep the mag starter, or get rid of it???
I am kind of a run what you brung person. So it is too late now, this machine is pretty much how it is going to be. Shame, I passed on a nice Monarch 15" lathe about 3 weeks ago, it sold for $1050 at auction. The monarch was in way better shape than the Standard Modern I have now. The price on the SM lathe was too good to pass up, at free to start, and pay me something you think is ok if you get it running.
Thanks for the advice so far.
 
still tripping one heater

hi well I dissassmebled and cleaned the contacts, and the magnets. Re-assmebled. the machine will run for a bit, and then trip one of the heater overloads. I swapped a wire around, on the supply, and the same heater still trips.
Any suggestions? besides getting a new starter. I am thinking about a new starter, but would prefer not to have to go that route yet.

thanks
 
could be the motor
do you know anyone that could meg it for you
have you measured the draw on it while running?
have you tried disconnecting the motor to see if starter will hold without motor load?
 
Thanks for the reply. my phone a friend electrician gave the same advice to check the amp load per leg at the motor while it is running. Also I thought to swap the offending heater to another position to see if the problem follows the heater. Heaters are available for less than $5 on ebay. Also I never got a response is there any way to bring up the manufactured leg off the RPC to a more proper voltage? like a 200v to 240v transformer???

I would have liked to just swap the motor on this for a single phase motor, but the electric brake is built onto the back of the drive motor, and it is a bit intimidating. The brake is almost as big as the motor. Do some people just go brakeless when they repower? If I went with a VFD. would I still have the magnetic starter? It seems like a lot of trouble to do away with the mag starter and the drum switch? I would not be sad to see the mag starter go away, but doing away with the drum switch seems to be counter productive. Could a VFD be set to just output 230vac 3-phase, and I would hook it into the same place that the original wiring hooks up?

thanks again for the help I will try and update with some more voltages and amp loads this afternoon.
 
As a certified cheep bastard I have use obsolete/ antique motor starters many times rather than replace them.

Motor starters buzzing on phase converters is something I have encountered many times.

Now I ALWAYS drive the starter coil with the two legs that are not generated, and rarely have any trouble. More than once the wild leg has been the problem. I cant give you a good reason why this solves the problem, other than the wild leg is just a little weak.

If the motor direction is wrong, reversing the machine simple. Just swap the two good legs and you wont have a problem.




I usualy bench test the starter before reinstalling it in a machine.

Start by connecting directly to the coil, and pluggin the coil into proper voltage.
If it buzzs, clean the surfaces on the magnet and verify that all the little moveing parts are clean and move freely, then try again.
If it still buzzes, chances are their is rust between the plates that create the magnet. I have not solution for this issue.

Once you know the coil works, move on to the contacts in the relay. They usualy need a bit of filing to get good contact if the crosion mites have set up camp.

The biggest problem with recycling old motor starters is finding the proper heaters and coils. Sounds like you have those.
 
I moved the heater from the leg that was always tripping, to a new position. The amperages that I got while the machine was running are. L1-7.3-7.6A, L2 6.1-6.5A. The 3rd leg had about .3-.4 amps (oh oh that does not sound good) , until the direction was reversed, then it had the 6.4 amps. Also the unit did not trip out the heaters until I switched to the highest speed, then it tripped the same position that has always been tripping, i will call it L2, the center position on the starter. But today after the machine would not actually make it to full speed, it also tripped out another of the heaters. This was new, as up till now, only one heater had been tripping. The machine will not make full speed 2000rpm without tripping out. I tried 1400rpm, and the machine got up to speed, but tripped out both heaters pretty quick, Same on 1000 rpm. Once the machine starts to trip out, it becomes more and more frequent. I gues the heaters are more sensitive once they are already warmed up. But the heater I moved did not trip out.
I guess I am missing something, I thought all 3 legs would be at voltage when the motor is running? or do I have a serious problem? Maybe I was not checking at the right place. I did not check in junction box at the motor itself. I checked at the drum switch where the motor wires all go. I only checked 3 of the black wires, i did not check the green ground.
my phone a friend electrician says I have a burned out winding in the motor. I guess that makes sense, but why does the the bad winding NOT have amperage in one direction, and then switch directions, and it gets amperage, but one of the other legs goes out??

ok thanks
 
oh I forgot to mention. once I cleaned the contacts the starter is not buzzing anymore. but now I think I have bigger problems. possible a bad winding on the lathe motor? the motor guys tell me it costs about the same to re-wind the motor I have, or buy a new one. problem is no one has found a new motor yet.
Can I switch to a single phase motor and just ditch the brake????, or maybe set up a foot brake of some sort? it is just me in the shop no one else to worry about
 
Its your lathe, you can do what ever you want.

Things to consider.
Is the motor a standard NEMA frame. If so, finding a new motor wont be a big deal. If not, it might be cost effective to rewind.

Single phase Vs 3 phase.
Single phase machines are easier to resell for home shop use.
Many folks feal that 3 phase motors are a bit smoother running and that shows up in your surface finish.
3 phase motors are a lot less expensive and relitively easy to come by on the second hand market.
3 phase motor + VFD gives you a lot more speed control and some VFD's have breaking.

Breaks on a small lathe are not a deal breaker in my opinion.
They allow the machine to stop quickly so you can inspect your work and save you a lot of time. You can probably set up some kind of mechanical break to do the job if you feel you need one.


If it were me, I would do some simple checks on the motor before tossing it - you have nothing to lose, right.

0, unhook all belts and release the break, spin the motor by hand and verify it moves well, no bad bearings, or other hitches.

1, Check the leads and verify the wiring patern is correct. Its easy to mistake a 6 and 9 or not get everything hooked up correctly in the motor head.

2, Disconnect all the leads and measure the resistance accross them. If something is badly wrong it will jump out at you.

3, Confirm the break is working properly. It could be a big source excess current consumption. (if your dirving an electrical release break with the wild legs it might not pop competely free)

4, set it up on the bench with a known good motor starter and wire it up. Start it and record the current and voltage. Then swap the wires around and measure it again. Continue until you have exhausted every correct wiring patern. See if you can confirm that you have a bad field. Also pay attention to the temperature rise. If you have a big problem it will probably get hot.

If the motor is bad, one of those checks should show it. If the smoke stays in, the problem could be some where else.
 
If you have lost current in only one direction, you have a bad contactor. The contactor that swaps 2 of the 3 incoming lines to reverse the 3 phase motor.

There must be a bad contact there, and you are losing (most of a phase)
 
i am guessing that you are talking about contacts coming out of the drum switch. I did not think of that. That is something to check. as a replacement motor for this is going to cost a small fortune, and a rewind sounds like it is almost as much as new.
I will check the drum switch with a ohm meter

thanks
 
i agree whole heartedly that the brake is a nice option but in no way a deal breaker on a garage lathe.
hell
are you sure the brake is working right?
if that thing is dragging it could easily be whats overloading the system.
fillet it out
and don't look back
 
Hi all, I am reviving this old thread. I work overseas a lot, so getting this lathe to work has been way on the back burner. I am still trying to get this machine to work properly. I did take the motor to the shop, I was not able to see the testing, but the tech said there was nothing wrong with the motor; that it was in very good conditon, and the brake is super strong.
So I did not burn out a winding or anything like that. I have not tried to run the lathe since I got the motor back from the shop.
I have been seriously considering getting a VFD to run this machine, and getting rid of the AB starter.
The VFD salesman i have been talking too, Said I can not use the VFD in front of the drum switch. I have done some reading here, and I understand that I can convert the drum switch into a low voltage control for the VFD. That seems understandibly easy enough for me to figure out with some help.
BUT what am I going to do about the E-brake on the motor and the VFD?????
Any help there would be apppreciated.
again the Lathe is a Standard Modern 13-40 with a 3 HP 220 3 phase motor with built in E-brake on the motor.
Oh and the motor tech said that a replacement for this motor with brake would be well over $2000. Too me that is just crazy high.
So any advice on a VFD to work with the drum switch, and the electric brake would be appreciated.

thanks
 
I didn't see this thread back in 2011, otherwise I would have responded.

From your description, you have a standard non reversing starter (just 3 sets of contacts, one coil) and a drum switch right? In that configuration it is the drum switch that is swapping 2 of the leads to make the motor reverse. So since you know that the contacts of the starter are OK, but you lose power through one pole when running in one direction but not the other, that means your drum switch contacts are bad. Most of them are not made to be repaired, you just replace it.

A few general notes though:
1) NEVER file contacts on a motor starter, you are killing them with kindness. The pitting is SUPPOSED to be there, it increases the surface area that is making contact. The peaks on one side will match up to valleys on the other side. So when you file them, you are removing that contact area, which increases the resistance, heats them up more and makes them start all over again making peaks and valleys, which ACCELERATES their demise about 5 fold.

2) The A-B 709 starters were obsoleted back when I started in the business in 1978, so that one is pushing 40 years of service. Even though you can replace the contacts and coils, other mechanical components wear out. The buzzing may be something that you cannot fix now.

3) FWIW, the overload relays in the 709 starters only had 2 heater elements instead of 3, which is now illegal.

If you yank it and go for the VFD, no switches on the load side of the VFD, it can damage the transistors (and here come the arguments saying it's not true, but read the VFD manual, it will tell you no). But you don't need the drum switch to reverse the motor any more anyway, the VFD does that electronically. So if you like the drum switch as a switch, you just need to find two sets of working contacts, one that closes in the Fwd direction, one that closes in the Rev direction. then using those as DRY contacts, meaning NO power on them, you wire them up to the digital inputs of the VFD that you program to be "Run Fwd" and "Run Rev". Boom, done.
 








 
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