Model K starts, runs for 3 seconds, then motor stops - updated!

[tx656]

I have a Monarch Model K 16 x 54 (5HP). Bought it over a year ago. Seller started it up, ran it through the gears, etc. So all good there.

Based on tags on the machine it looks like it was originally installed at Corpus Christi - U.S. Army Transportation Aeronautical Depot Maintenance Center "ARADMAC". An Army aircraft maintenance center. Overall the machine is in good condition!

Today I finally got it wired up. I used a 4 wire 10 gauge cord and plugged it into the 30 amp outlet I use for my Wells Index 745 vertical mill (albeit much smaller motor).

Power supply is a 10 HP American Rotary converter feeding a 3 phase panel. 30 amp breakers, minimum 10 gauge wiring all the way to the machine.

My RPC works great on the Wells Index 745. Am using the same outlet. X wire is the black, Y wire is the red, Z wire is the 'orange' manufactured 3rd leg.

When I power up the lathe the motor comes on, runs for 3 seconds, and then the motor stops. To get the motor to start again I have to reset the Furnas dual voltage coil on the left side of the Monarch's electrical box.

The power is entering the Furnas box form the left side of the box. The wires feeding up from the left most vertical conduit do not look like they have been connected to any power supply for a very long time.

Diagnosing electrical...not a gift of mine...so turning to the board for thoughts/advice.

Video link

The hum at the beginning of the video is the RPC. The hum is not the Monarch trying to start or anything like that.


I won't be leaving the wire entry into the switch like you see in the pic. Tonight was all about checking if the lathe would 'run'.

 

[johnoder]

"heaters" (thermal overloads) are probably rated for 440. I'll assume you are trying to run it on 240 which uses twice the amps as 440
heaters are often in lower section of magnetic motor starter.

 

[dalmatiangirl61]

Did you change wire connections, or check to make sure motor was wired for 220v, assuming that is what you are running? And thermal overloads as mentioned /\

 

[tx656]

Did you change wire connections, or check to make sure motor was wired for 220v, assuming that is what you are running? And thermal overloads as mentioned /\

Yes on running 220v. No I didn't check how motor is wired. I'll look at that.

 

[tx656]

"heaters" (thermal overloads) are probably rated for 440. I'll assume you are trying to run it on 240 which uses twice the amps as 440
heaters are often in lower section of magnetic motor starter.

I'll go check that now. I guess I'll learn quickly if heaters are labeled 220 vs 440?

 

[johnoder]

I'll go check that now. I guess I'll learn quickly if heaters are labeled 220 vs 440?

May not be that obvious. Some heaters just have a makers number which to that maker means a certain number of rated amps

 

[dalmatiangirl61]

I'll go check that now. I guess I'll learn quickly if heaters are labeled 220 vs 440?

Google "Furnas heater chart", from there you can figure amp rating of what you have, and what you will need if it was previously being run on 440v. Heaters are sold quite inexpensively on ebay.

U.S. Army Transportation Aeronautical Depot Maintenance Center is part of the old CCNAS, I'd bet money its wired for 440v

 

[cyanidekid]

obviously confirming the voltage the motor is rated for is step one.

did you re-connect the motor windings to switch from 440 to 220? if you didn't , it will actually draw less idle current on the lower voltage. also "idle" amps is going to be much less than "full load amps'. the motor starter heaters are rated in amps, NOT volts (and to some extant they are different depending on service factor and starting current)

you didn't mention voltage at all, so thinking you aren't familiar with industrial type power? "3 phase" isn't one thing, as you must be figuring out, its just one aspect of an AC supply. the largest motor ive seen a plate on was 6000 HP and 6600 volts, and it was a 3 phase motor, of course. air handler in a power plant in Queens NY. that baby moved a LOT of air!

 

[tx656]

I'm supplying 3 phase 220v w/manufactured 3rd leg. I did not initially check if motor was wired for low or high voltage. I'll look at that.

 

[tx656]

I pulled off the motor cover and removed tape from one of the connections. "4, 5, 6" are connected. Motor is wired for 'lower' voltage. (Was kind of hoping to find it was wired for 'higher' voltage.

 

[tx656]

Here are the volt readings in the panel that feeds the 30 amp outlet I connected to. (I figure someone will ask)

L1 L2 = 251
L1 L3 = 244
L2 L3 = 254

L1 Ground = 122
L2 Ground = 221
L3 Ground = 122

 

[tx656]

I read elsewhere tonight that an exposed lead wire in the motor could cause this. When I pulled the motor wiring junction box cover off to check how lead wires were paired I saw one lead wire with some missing insulation. The wires are almost 60 years old so....there could be others. Maybe pulling the motor and replacing the numbered wires is in order? Is that a 'home shop' kind of job or best left to a motor rebuilder?

 

[Mr_CNC_guy]

To my ear, your motor never came up to full speed. It should have no trouble reaching
full speed in 3 seconds unless the motor has a heavy load attached.

This is the classic case of a shorted turn in one of the windings. The short acts like
a brake on the motor, and it can't spin up to full speed. If you can see the stator
windings, ensure that they are all the same color. One might look "toasty".
If you have a clamp-on amp meter, all the windings should have the same current
during that 3 seconds. I assume that the motor spins freely by hand?

Sometimes you can identify the bad winding by measuring its resistance. The 3
windings should be the same. A better test is to measure their inductance.
Does your meter have an inductance setting?

 

[nt1953]

Looking at the picture of the Furnas coils, I see that they say dual voltage and show wiring diagrams. So, how is it wired?

Do not assume anything about the wiring on the motor. If it has been rewound, it may or may not still be wired according to the name plate.

If the motor wiring (low or high voltage) matches the Furnas coils, then everything is probably per diagrams.

Make sure it all is wired for low voltage.

I took my motor to a shop and had them recoat the windings and put new leads on.

 

[GrantGunderson]

I read elsewhere tonight that an exposed lead wire in the motor could cause this. When I pulled the motor wiring junction box cover off to check how lead wires were paired I saw one lead wire with some missing insulation. The wires are almost 60 years old so....there could be others. Maybe pulling the motor and replacing the numbered wires is in order? Is that a 'home shop' kind of job or best left to a motor rebuilder?

The first thing I would do in this case would be to check all of the leads with a Megger. You can rent them, or Klien sells a unit on Amazon for around $100. If the motor fails the megger test than it needs to be rebuilt end of story. If it passes than move on to verifying it is leads are properly wired for the low-voltage configuration. You can use a multi meter to do this. Then move on to look at the starter system and it’s wiring.

 

[tx656]

Looking at the picture of the Furnas coils, I see that they say dual voltage and show wiring diagrams. So, how is it wired?

Do not assume anything about the wiring on the motor. If it has been rewound, it may or may not still be wired according to the name plate.

If the motor wiring (low or high voltage) matches the Furnas coils, then everything is probably per diagrams.

Make sure it all is wired for low voltage.

I took my motor to a shop and had them recoat the windings and put new leads on.

The terminal jumpers are right below the black and red Furnas logo in my pic. Their placement indicates to me the unit is set up for 'low' voltage.

 

[GrantGunderson]

The terminal jumpers are right below the black and red Furnas logo in my pic. Their placement indicates to me the unit is set up for 'low' voltage.

Are those jumpers for the motor or the coils? I can’t tell from the rats nest wiring in the pic. Also when running on a RPC motor / generators at least like what is used on the 10EE need a jumper moved to account for the wild leg on the main contactor. So you might need to look at that.

 

[dalmatiangirl61]

Time to look at the heaters, are there 3 per contactor, or just 2 per contactor? Working on first cup of coffee and I can't tell with pics. If only 2 per contactor, make sure the generated leg (looks like L2 by what you posted above) is not going thru heater, or thru the contactor coil.

 

[tx656]

Are those jumpers for the motor or the coils? I can’t tell from the rats nest wiring in the pic. Also when running on a RPC motor / generators at least like what is used on the 10EE need a jumper moved to account for the wild leg on the main contactor. So you might need to look at that.

I don't know enough to answer your question re 'jumpers for motor or the coils'. I'd say coils.

 

[tx656]

Time to look at the heaters, are there 3 per contactor, or just 2 per contactor? Working on first cup of coffee and I can't tell with pics. If only 2 per contactor, make sure the generated leg (looks like L2 by what you posted above) is not going thru heater, or thru the contactor coil.

I don't know how to check if there are 2 or 3 heaters per contactor. (there isn't that much in the box...but I couldn't tell you what a the 'heater's look like. I presume they are behind or a part of the coils?) I have been looking info online re contacter vs coil vs heater and its more than a littel gray to me. I cleaned up the wiring 'some' by getting rid of the excess and removing wiring that had been cut at it's exit point from the lathe base. I suspect the 'non-connected' wiring was originally for a coolant pump. I also removed two wires that were feeding an hour meter. A cleaner picture is attached.



I did 'test' it by running it again this afternoon. It ran for maybe 6-8 seconds before cutting out. This time when the motor stopped...it was because it blew the 40 amp breaker that feeds the rotary phase converter.

At this point I think the 'healthy' thing to do for the machine (and for me) is to remove the motor, the Furnas control box, and the forward/reverse/stop assembly and take the whole works to a motor repair shop.

If anyone has a shop in the Dallas/Fort Worth area they like please let me know.