Thread: Dead winch, motor reversal issue

Customer has a fairly new winch. Something like this:




which has been working OK for a month, but suddenly stopped working in one direction.
Can drop it down, but not lift up!!!


No problem, thinks I, broken switch?

Go there today, momentary DPDT switch seems OK. Look into circuit:
IMG_3743.jpg IMG_3744.jpg
there is a dual capacitor. 15uF and 40uF.
I've never actually played around with reversing single phase motors.
I'm guessing one cap value drives it forward, and one is sufficiently out of phase to drive it backward?

I test the cap(s?) with a little LCR:
IMG_3745.jpg IMG_3746.jpg
and they seem OK.


Then I try something. Swap the cap wires on the switch.
I thought this would cause the "up" position to go down.

It didn't. The up position gave a slight motor hum for a microsecond, then nothing.
And the down position still went down.


Very confused!!!!!

Hi Nigel,

A bad connection to the cap can still give you a good capacitor reading on those digital meters ! Whilst to get a capacitance reading and what seems like a good esr, there is not enough current in the circuit to be sure that the capacitor is good under operating conditions.

Anyway reversing a single phase motor is not difficult. Simply reversing the start coil connections will do that. Which is what the lower switch does. I would check that the switch actually works !

There may be a faulty limit switch or adjustment somewhere in the lifting mechanism.
If you have a in line current meter, check the current in both directions.
It is unlikely to be the capacitor given that it works ok in one direction.

Paul

Originally Posted by paul33

There may be a faulty limit switch or adjustment somewhere in the lifting mechanism.
If you have a in line current meter, check the current in both directions.
It is unlikely to be the capacitor given that it works ok in one direction.

Paul

Those cheap hoists have a ring arrangement and a disc clamped around the cable which activates a limit switch to stop the up operation.
Probable a issue with adjustment of the limit switch or faulty switch. For their price they are a handy hoist. We used a few where I previously
worked to move motors and Vac pumps from and to mezzanine platforms. Had a few instances of the up limits failing.

How many wires going to the motor itself?
If its 3 , it might be similar to a lathe I worked on once. It had a centre tapped winding. Centre tapping was neutral and one end was Active for Forward, the other end was Active for reverse.
It used the same configuration switch that a 3 phase motor would use.....effectively reversing 2 phases.

Originally Posted by Sterob

How many wires going to the motor itself?

Unknown. Four from the handset up, but I didn't have a 3m high ladder to investigate the other end.
Tomorrow morning's problem

Almost guarantee a molten switch. Possibly the change-over switch on the pendant. They are awfully wimpy for the starting current of those motors. Or the limit switch as mentioned already. Same crappy quality....

Took the tall ladder, and investigated.

Paul and Sparksy were correct. The limit switch was somehow jamming.

The cable goes to a pulley, and its support was somehow twisting:
IMG_3762.jpg



I twisted the pulley around a little, attached an extra brace:
IMG_3763.jpg
and instructed the owner to check the limit switch (cable guiding loop) is free, if the fault ever happens again.

Hope they dont use it for much load, way that pulley is setup guiding the cable to end of the drum it will bunch up on that end and put strain on the cable. Should have been 2 pulleys used, first one a bit lower to drum and central and the other in similar position to existing. Could do away with the limit switch as it wont work anyway.