# Man-lift elevator motor questions



## subelect (Nov 25, 2007)

I am working on an ancient 3 phase, 240 volt man-lift. The renter tells me that the lift went to the top by itself during the night and was not working, 3/4 of the way up.
I opened up the Cutler-Hammer controller and found: 
1. Overload contacts were jumpered out. 
2. Safety interlocks on the gate of the man-lift were removed.
3. I unhooked the control wires (both sides of the ckt) and manually operated the contactors. Motor sounded like it was single-phasing, but it blows phase A fuse immediately when it is energized. Disconnecting L-1,2 & 3, I get 240 volts phase to phase when energized; 44 volts across one set of wires when not energized (with a Fluke 116); 2 ohms across the windings and 100 Megohms to ground (with a Biddle).
The 1 & 1/2 hp motor has a brake on the free-end (opposite the coupled end) but I can't remove the end-bell without pulling the motor down from its mounting. The brake has 2 "dog-ears" that I believe release the brake when pressed. 
The motor wiring diagram does not show any connections for the brake. 
-Are the connections for the brake inside the motor frame?
-Are the dog-ears supposed to mechanically release the brake?
-Is 44 volts across one phase enough to get a 3 phase motor moving on its own? 

I will have to address the jumpered safeties and overload after I get the motor working again. 
Thanks
Rick


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## jhall.sparky (Jun 14, 2011)

subelect said:


> I am working on an ancient 3 phase, 240 volt man-lift. The renter tells me that the lift went to the top by itself during the night and was not working, 3/4 of the way up.
> I opened up the Cutler-Hammer controller and found:
> 1. Overload contacts were jumpered out.
> 2. Safety interlocks on the gate of the man-lift were removed.
> ...


WOW! What a booger. 2 ohms that doesn't sound healthy. Can you post pics of the coupled set-up and brake?


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## MDShunk (Jan 7, 2007)

Lucky you! 

Sorry, brother, but I fear you're in over your head. We need pictures!

(I once worked on a wooden elevator made by "The Conestoga Elevator Company". Controls on a slate backboard ).


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## micromind (Aug 11, 2007)

Most brakemotors are dual voltage wye wound. The brake coil is usually 120 volt, and it uses one of the motors windings as a sort of autotransformer to get 120 from 240 or 480. The brake coil is connected to T1 & T4, or T2 & T5, or T3 & T6. Regardless of the incoming voltage. 

2Ω would be on the high side of reasonable, but it's likely ok. 

I suspect the brake is connected to T1 & T4, and it is shorted. This would explain the øA fuse blowing. 

Here's how I'd go about this; First, you'll need to open the motor terminal box and disconnect the brake leads. they're usually red, but not always. Measure resistance across these leads. It should be between 2 and 20Ω. If it's open, then the brake coil is bad. If it's shorted, the coil is bad and it's the reason for the fuse blowing.

If the brake coil checks out good, I'd measure phase to phase voltage under load, at the starter, with the brake coil still disconnected, but the motor leads properly spliced. A to B, B to C, and C to A. If you're using the stalled motor as the load, don't leave it energized for more than a few seconds, and let it rest for a minute or so between tests. Also, measure current. The locked-rotor current of a 1-1/2HP 3ø motor at 240 volts will be 20-30 amps. A bit less at 208 volts. 

If all this checks out ok, then the motor is ok, and you have a mechanical problem.

The dog ears on the brake are indeed a mechanical release. Some of them push in, some push out, and others rotate. You'll just have to play with it a bit. If you can, energize the brake coil with a separate 120 volt source. You should hear it click in and out. If it doesn't click, either the coil is bad or it's jammed. 

Can you hold the brake open manually and turn the shaft at the same time? There's a slight possibility that the elevator mechanism is jammed, and the motor and brake are ok, but the fuse blowing would indicate an electrical problem. 

Are the fuses time-delay? A fast-acting fuse will blow right away in a motor circuit. 

Once you get this solved, the controls will likely be somewhat of a nightmare..........


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## subelect (Nov 25, 2007)

I had disconnected the L-1,2 & 3 inside the motor terminal box when I took the voltage readings. I did not see any leads for the brake; just the T-1 thru 9 for the motor per the diagram. 
When I rotated the dog-ears, I am laying on top of the motor; there is no room for anyone to reach up and try to see if the shaft is free to rotate.
Thanks for the advice; I am going to have to uncouple the motor, rotate it so that I can get to the brake's cover removed and see what is going on in there. 

On a side note, the original electrician ran IMC all the way into the motor terminal box. Whoever it was, they were a lot more motivated than I am; I usually terminate the last foot in LTFMC. I can't imagine how much work this must have been using plug-in drills and hand-threading all of their IMC. 

Probably won't be bored today,
Rick


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## McClary’s Electrical (Feb 21, 2009)

micromind said:


> Most brakemotors are dual voltage wye wound. The brake coil is usually 120 volt, and it uses one of the motors windings as a sort of autotransformer to get 120 from 240 or 480. The brake coil is connected to T1 & T4, or T2 & T5, or T3 & T6. Regardless of the incoming voltage.
> 
> 2Ω would be on the high side of reasonable, but it's likely ok.
> 
> ...


Sorry, but alot of the brake motors I've seen have the same voltage coil as the motor for obvious reasons.


Also, 2 ohms sounds about right for a motor that size.


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## subelect (Nov 25, 2007)

I saw the retired manager of the facility this morning over coffee. He brought up a good point about uncoupling the motor. 
Since the lift is not on the bottom, the only thing holding it in place is the brake and gear box tension. 
Before I can pull the motor out of there and check the condition of the brake solenoid, I need to support the weight of the lift.
If I had not stopped to talk to that old man, it could have been really bad. 
Rick


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