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Intermittent starting problem 1945 10EE MG

lectrician1

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Mar 6, 2012
Location
Las Vegas
I installed a 115v variable DC power supply to replace the failed exciter. the machine seemed to be working fine although i only ran it a few times. Now it has developed a problem starting. The machine will start flawlessly 10 times in a row at all different RPMs. Then for no apparent reason, I will try to start the spindle at around 800rpm and the generator slows down severerly and cannot start the spindle motor. The spindle won't start unless I turn the variable speed down to about 500 rpm.

Then the problem seems to go away for a while. then it returns again.

I thought it might be a problem with the variable speed rheostat, so I sprayed DE-OXIT on the coils but no change.

I just got this machine so the problem might have existed before I added the new power supply.

Is there a starting winding on the generator with a centrifugal switch that may be sticking or something like that?

Thanks
Rich
 
There are no starter winding on a 3 phase motor or dc motors. When you are having the problem break out the voltmeter and check the field voltage on the spindle motor at 800 rpm setting it should be about 115 Volts dc.
 
Usually F1 and F2 in the pecker head But remember this machine is 74 years old so the labels could be hard to read.
 
i went across f1 and f2

voltmeter across f1 and f2

under approx 650rpm the meter reads near input voltage coming from the power supply

i varied the voltage from the dc power supply from 90v to 122v dc. still intermittent problem

as i slowly turned up the rpm past 700 , the voltage across f1 and f2 dropped steadily with no major spots where it dropped to zero or anything like that.

anyway i used some compressed air to clean off the back of the DC panel. i thought i saw some swarf that might have been shorting out two terminals but i am not sure.

i also cleaned the contacts of the relays in the dc panel and the contactors.

Seems to be working right now. Spindle starts at any speed.

Tomorrow may be a different story.

thanks

I'll keep you posted
 
problem is still there intermittent

But I've found that when the generator bogs and will not start the spindle above 750rpm, if i manually press in the FA relay, the spindle will start.

So i think the problem has something to do with the FA relay.

What is the sequence of operation of the FA relay?

Mine does not pull in at any time

On my FA relay mounting board, there is a 4000 ohm resistor in series with one of the coils.
That resistor is bad.

I had a 3000 ohm resistor laying around so I inserted that in series with the coil but the FA relay still does not pull in.

There are two separate coils on the relay
one reads 900 ohms
one reads short circuit.

What do you think?
 
I do not have a manual for the MG lathes but the FA relay is used when the motor current is high it will apply full field voltage to the motor to get it up to base speed then when the current drops back to normal it drops out the full field voltage in order to get up to final speed. not knowing how the FA relay gets it voltage from I cannot help you I think it will get it from a current transformer. The dead short coil could be a current coil that senses the motor current and the other coil is bias for the FA relay see if you have voltage on the higher ohms coil.
 
I installed a 115v variable DC power supply to replace the failed exciter. the machine seemed to be working fine although i only ran it a few times. Now it has developed a problem starting. The machine will start flawlessly 10 times in a row at all different RPMs. Then for no apparent reason, I will try to start the spindle at around 800rpm and the generator slows down severerly and cannot start the spindle motor. The spindle won't start unless I turn the variable speed down to about 500 rpm.

Then the problem seems to go away for a while. then it returns again. ...
You say that "the generator slows down severely". That sounds like something is either overloading the output of the motor/generator (MG) or perhaps the way that the "115v variable DC power supply" is connected to the AC input is causing problems. Please tell me more about the DC supply and how it's connected to the machine. There really shouldn't be that much load on the spindle motor just starting the spindle at 800 RPM. Are you in open belt or back gear when you're doing this?

You don't have to go into the pecker head to get to the spindle motor's field leads. You can read from F2 to E2 on the terminals at the bottom of the DC panel. Check the output voltage of your DC supply (terminals E1 to E2) when the problem is going on and check the input voltages to the AC section of the MG: go to the terminal panel on the front of the MG, check the AC voltages T1 to T2, T1 to T3 and T2 to T3.

I assume that this is a square-dial 10EE. Is that correct?

Cal
 
round dial 10ee
intermittent problem
sometimes when i try to start the spindle above 750 rpm the generator bogs and starts making a sounds like it is overloading. Spindle won't start.
I only let this go on for a few seconds because i dont want to blow anything
if i turn downn the variable speed to around 650 the problem goes away. Spindle starts right up.
Today i tried manually pressing the FA relay while the generator was bogging and it worked. the spindle started
so i looked closely at the Really and checked the wiring and resistors.
everything seems ok but the FA relay never pulls in even though there is a constant 60v dc to the one coil.
 
You may have an issue with the FA relay, but there's more to it than that. I've NEVER heard of a bad FA relay causing the MG set to slow down. Something is very wrong if that's going on. Assuming that you have a decent source of 3-phase power and that your wires are adequately sized, the MG should purr along happily and never slow down. If the FA relay is bad, the spindle will be slow to accelerate, but the spindle motor should never overload the MG set to the extent that it slows down. That's why I'm asking for the voltages to the MG's AC section, so we can tell if your input power is sagging for some reason.

If this problem just developed after replacing the exciter with the mysterious variable DC supply, then it's a huge coincidence for the FA relay just happened to fail. It's more likely that it was bad all along. Again, what is the nature of the variable DC supply and how is it connected to AC power?

Where are you getting the 3-phase power for the machine? Rotary converter, static converter, power company, something else?

Cal
 
machine is being fed with a rotary phase converter 15hp
my house voltage runs a little high. sometimes the high leg is 250v
I got this machine a few weeks ago from a previous owner that got it from the government but he never ran it.
So there is no info on the previous condition of the machine. One of the previous owners had a dc supply mounted on the front of the machine.
It was a simple home made box with some capacitors and a transformer. It was supplying 85v DC. I didn't run the lathe that much with the home made dc power supply. So I can't say that this current problem existed or not.
I bought a Variable 115v DC 3amp power supply on ebay CHINESE. The power supply input is 220v AC.
I removed the non working exciter and installed the new power supply in that space.
I picked up the 220v AC input for the power supply from the generator pecker head. I chose two phases of the three phase AC terminals on the bottom left side of the box.
The DC output from the supply went to the two upper right terminals in the pecker head. Those upper right terminals are where the original home made supply was connected.
The new power supply has a digital voltmeter and ammeter on the front. I checked the voltage with my FLUKE meter and it is consistent with the power supply meter.
the DC output voltage from the power supply does not fluctuate even when the generator is bogging. So i don't think the problem is with the power supply. Tomorrow I will disconnect the power supply from the generator feed wires and pick up the supply voltage from somewhere else. I'll see if anything changes. Last night I fit a 7" three jaw chuck and a 7" 4 jaw chuck to two D1-3 back plates. The lathe was operating flawlessly at all different speeds mostly under 800 RPM. Heavy cuts with Dozens of stops and starts with no bogging. This morning i started the machine and it bogged twice at around 850 rpm. I turned the speed control down, the spindle started and then the problem went away. All the while i never see the FA relay pulling in.
 
i have a fluke 77IV and an amprobe.

I checked the voltage to the coil on both ac and dc with the fluke. 60-61v dc and about 1v AC
i dont have a scope

power supply is WANPTEK KPS1203D china. 0-120vDC 0-3A 120/220 ac input. IDK ripple
 
1945 was the very end of round-dial production; as far as I know, the last round-dial was built in July of 1945. Every 1945 round-dial that I've seen thus far has had the same motor/generator set and DC control panel that was used in square-dial 10EEs. Based on the photo of the MG terminal panel that you posted, you don't have a square-dial MG set. That's important because the DC panels are significantly different.

I need to see a good photos of the DC control panel and the terminal panel on the MG. The ones you posted are very low resolution and it's hard to see what's going on.

What is the serial number and build date of the machine?

Regardless of which MG set you have, the AC inputs to the MG are the bottom three terminals on the MG terminal panel. For the third time, what are the voltages between those terminals (T1, T2 and T3), under normal circumstances and when the machine is "bogging"?

Cal
 
serial 28386
date 7-1945
voltages T1-T2 263v
T2-T3 247v
T1-T3 275V
under normal conditions spindle idle
same when the spindle is turning

i couldn't get the voltages when bogging

i just went out there and started the machine
it bogged the first two times i tried to start it
i got a video of it. PM me your cell and i will send you the video and some better pics

the machine only bogged twice, then started normally
it may only bog when it cold
i couldn't get it to bog again to measure the voltages
 
serial 28386
date 7-1945
voltages T1-T2 263v
T2-T3 247v
T1-T3 275V
under normal conditions spindle idle
same when the spindle is turning

i couldn't get the voltages when bogging

i just went out there and started the machine
it bogged the first two times i tried to start it
i got a video of it. PM me your cell and i will send you the video and some better pics

the machine only bogged twice, then started normally
it may only bog when it cold
i couldn't get it to bog again to measure the voltages
You'll have to e-mail them to me. PM sent.

Do the voltages sag when the spindle is started?

It looks like the artificial (generated) phase is on L1. You can verify that by checking the voltages from ground: the real phases will be about 120 VAC, the artificial phase will be higher. Assuming that you have the original Cutler-Hammer AC contactor, only two of the three phases pass through the overload heaters, so you normally want the real phases on L1 and L2. (That involves moving a wire on the contactor so that the starting circuit is on the real phases, see this link: 10EE MG Starter Circuit with Cutler-Hammer Contactor - Revised)

We need to find out if the voltage is sagging when the MG slows down. If your meter has a hold feature and can be set to capture the minimum voltage, you might want to set it up after the MG is running, but before you start the spindle the first time. Reading the artificial phase to ground will tell you if it's sagging on startup. If you have a clamp-on ammeter, you should check the phase currents as well.

Your phases aren't very well balanced, so you may need to adjust the run capacitors, especially if odd things happen when the load changes. If the RPC is otherwise well balanced when used with other equipment, you can add additional capacitors to the 10EE, after the AC contactor.

Cal
 
Bogging is back

Bogging problem is back.

this time i measured the voltage drops between phases
in the motor/gen terminal box

T1-T3 275v dropped to 220V during bogging 55v Drop
T1-T2 258V dropped to 210V 48v drop when bogging

T2-T3 245V dropped to 240v this phase only dropped 5V during bogging

the wires from the motor starter in the headstock to the generator have been changed recently by a previous owner they are #10awg.

Any help or opinions are greatly appreciated
thanks
Rich

Are there brushes in the motor/generator that need replacing or maintenance?
 
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