Electric winch polarity

[Csail]

I bought a new 12v electric winch at a boat jumble and fitted it in the apex of the garage roof , then hoisted the dinghy up (as was the plan) BUT it only winches in and to let the cable out is a manual wheel thing which is either locked or fully releases the load. If i reverse the polarity would it winch down or break something?

 

[Channel Ribs]

It will almost certainly be a DC motor and will cope with you reversing the polarity.

 

[VicS]

Reversing the polarity will reverse the current in both field and armature so it will still go the same way. Assuming it does not have a permanent magnet field. To make it run in reverse you would haveto reverse one or other of the two on its own.

I think

 

[Channel Ribs]

I reckon that is the three lugged versions, in either case reversing the wires will not do much harm (unless you are holding it and it spins out of your hand to fall on your foot).

 

[philip_stevens]

Vic,
I'm not going to argue, but I always thought that to reverse a DC motor, you only needed to reverse the connections. A single phase AC motor will always go in the same direction whichever way the connections are.

Going back to my Tri-ang train days with DC motors in the engine, if I reversed the polarity of the track, the train reversed.

I could be mistaken. If so, I will apologise in advance.

 

[William_H]

Phil Vic is right although itn depends on whether it has a permanent magnet field as many modern motors do or if it has a field generated by a seperate winding. The permanent magnetic field is fixed in polarity so reversing the power tot the armature will reverse the armature field so reverse the motro but if it has a field coil around the outside then reversing the supply will reverse both the armature and field coil magnetic field so the reaction is the same and motor goes only in one direction.
If it has a field coil you need to reverse the connections to that field for reverse operation by breaking the field coil connections and bringing out to a switch. The field coil in this case is usually in series with the armature (brushes) but in other types of motor the filed coil can be in paralell. A seires field coil gives very high starting torque and current while a paralell field coil gives higher power at speed. olewill.

PS occasionally the brushes are shaped and timed for one direction of turning but reversing doesn't usually cause a problem.

 

[misterg]

What holds the load when the motor is switched off?

If it is some sort of ratchet or spragg (sp?) clutch, then reversing the motor won't work unless you reverse the action of this, too.

Andy

 

[VicS]

[ QUOTE ]
Vic is right

[/ QUOTE ] Thanks Will I thought I was.

 

[pampas]

With field wound DC motors always reverse the armature circuit especially if inter poles are fitted,as the magnetic reluctance is greater in the iron carcass,ie treat the field coils as you would for permanent magnets.

 

[richardandtracy]

I'd be most concerned about there being a ratchet.

 

[philip_stevens]

That's OK Vic. I don't mind learning - still.