P&H crane motor - extra leads

[fsmyth]

Just got a replacement bridge motor - HEWH286, 15 H.P.,
1140 RPM, 460v, mfg. no. 286M1076 (3-phase/wound rotor)
for a P&H 35 ton crane. This motor has 4 extra, unmarked
leads, approx. AWG18. Can anyone identify them?
Wouldn't be a problem, but the motor started heating
immediately upon start after installation, so we would
like to know what the leads are - to eliminate them as
a problem, at least.
<als>

 

[waross]

Does the motor have an internal 230/460 volt brake? The original motor may have had the brake leads connected internally during a rewind. A draging brake will heat things up quickly. Failing that they may be temperature sensors.
If there is no brake I would suggest checking the contactors for open or welded contacts. When a motor fails, it occasionally damages the contactor. Also when a contactor fails it occasionally damages the motor.
yours

 

[fsmyth]

Nope. External brakes. Working.

Crane bridge has two motors (one on each end) controlled
by a single contactor. Other motor works fine.
(This is a 5-speed arrangement, using stepped rotor
resistance).
<als>

 

[waross]

Have you checked the resistor banks for a bad resistor, or a bad contact in a secondary contactor? Another possibility is shorted leads somewhere in the secondary circuit.
If there is a broken connection in the primary wiring the motor can be single phasing. With a two motor drive it can start with mechanical help from the other motor but will overheat. Is the motor pulling its share of load, or overdriving?
yours

 

[stardelta]

Any markings on the leads? do they circuit out and if so what is the resistance? I am thinking ETDs, thermal trips or heater-tapes.

 

[MikeHalloran]

You did check that rotation matches the other motor, right?




Mike Halloran
Pembroke Pines, FL, USA

 

[jraef]

LOL, Mike, I should have thought of that too.
Been there, done that on a large bridge crane drive control retrofit! Installing contractor tested the motors on the ground using the same VFD, but when installed on the bridge, the two different VFDs had apparently been programmed for opposite rotation in the previous installation because someone was too lazy to swap leads. We couldn't figure out what the heck was wrong for hours!

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[MikeHalloran]

It happens that I am now learning how to build bridge cranes.

... okay, I'm really learning more about now _not_ to...



Mike Halloran
Pembroke Pines, FL, USA