motor problem.

[darren adcock]

Simply I can't get it to work. When I continuity test across it's lugs it shorts. disconnect one wire and it shorts across the brushes. I'm unsure if this is normal. It's a Parvalux some of you helped me get a correct power supply for a couple of years back. Spec: dc 24v. amps 8. 120w. rpm 2800. 12/14 geared. I'm looking inside the back of the motor and it sure seems grubby in there. If I do get it working it might be worth a bit of tlc.

Thanks

Darren

 

[kellys_eye]

Such motors will show as good as a short circuit on a simple resistance check but this doesn't necessarily mean they are dud. 'Grubby' could well mean the commutator needs cleaning (the segmented copper bit). Have you checked the state of the brushes?

How are you powering it?

 

[darren adcock]

Hi mate.

The brushes both looked Ok to me, but I'll double check here with photos tomorrow. I'm powering it from a 12v 1.5a power supply.

I'll have a look inside tomorrow properly, there was all kinds of orange (didn't look like rust though) grub in there.

 

[darren adcock]

Oh I tried to run it off my bench power supply also but it triggered the current limit at around 1.5v. My bench supply runs up to 30v at 5 amps.

 

[kellys_eye]

Pfft - your power supply has no chance! 24V at 8A is the running voltage/current - it would probably take 20A+ to get that motor to start turning! This is known as switch-on surge. Unless your power supply can deliver a PEAK (instantaneous) current of 20A minimum you'll not get that motor to spin using it.

Slap a 12V lead acid battery across it and it might get going.

 

[Minder]

Try back driving the motor if you can, it may be hard if a high ratio gear reduction.
But you should get a generated voltage that is proportionate to 24vdc at 2800rpm .
Is it possible the G.B, has a problem?
You can use an automotive battery but care taken if there is a short circuit.
M.

 

[darren adcock]

Pfft - your power supply has no chance! 24V at 8A is the running voltage/current - it would probably take 20A+ to get that motor to start turning! This is known as switch-on surge. Unless your power supply can deliver a PEAK (instantaneous) current of 20A minimum you'll not get that motor to spin using it.

Slap a 12V lead acid battery across it and it might get going.

Oh ok. Actually I think I see what has happened. I had two 12v supplies, one rated 10amps the other the 1.5amp. I have this tendency to pick up any old power supply just in case. The 12v at 10a wasn't giving me an output so I assumed it was a dud from a car boot. Now I think what has happened is that this was the one I had used before but possible it has been burnt out by using it with this motor.

Initially when it worked a year or so go it would start but only after some short bursts of turning, it would take around 10 seconds to get fully turning.

I hadn't come accross Peak (instantaneous) current before, I guess this is why starter motors are used? I will read about this, thank you.

 

[darren adcock]

Try back driving the motor if you can, it may be hard if a high ratio gear reduction.
But you should get a generated voltage that is proportionate to 24vdc at 2800rpm .
Is it possible the G.B, has a problem?
You can use an automotive battery but care taken if there is a short circuit.
M.

I guess I've got to try it on a suitable power supply first.
I would try the car battery but It's for a kkinetic sculpture for an exhibitio and I know they won't be happy about a car battery being used (I've come accross this before)... it would be ideal to be able to use a power supply. Even if I have to get one made. I have various attachments for the motor for different purposes so it would be an investment.

I did try moving the motor manually (if this is what back driving is) but to no avail. I will try again tomorrow with some added torque

 

[darren adcock]

the intitial thread for this motor when I was asking for help is here. https://www.electronicspoint.com/threads/wiper-motor-wiring.280624/page-2#post-1708505

 

[darren adcock]

In terms of getting the motor initially running, does it need more power initially? the spec for the motor suggest 120w which is 12v x10a. So is it the initial start up for the motor that has potentially ruined the power supply?

 

[Minder]

I I know they won't be happy about a car battery being used (I've come accross this before)...

And why is that?
There are simple 555 based PWM controllers on ebay for just a few $$$'s that will give you a soft start.
Or build your own if you have the ability.
M.

 

[darren adcock]

They see it as a fire risk, something about not being able to safety test it or somert, I gave up trying to convince them otherwise. Actually when I've used battery arrays of 9v's they haven't moaned. Maybe I'll approach it again.

I've just found I have a PWM controller in my "to be used box" so I'll order a new power supply and see how I get on. I will also build my own so I have a better understanding

Thanks for your help

 

[Bluejets]

I did try moving the motor manually (if this is what back driving is) but to no avail. I will try again tomorrow with some added torque

You will not be able to turn the motor via the gearbox on the worm drive arrangement.
That's the nature of the worm drive. There are exceptions but I won't go into that.

 

[73's de Edd]

Sir darren adcock

If you use the adequate powering by a battery, initially with one wire connected, then take the other free one and make a short sweeeeeping on-off temporary contact, just as if you were striking match. If that gives a successful burst of rotation of the motor shaft, try progressively longer temporary power contacts. Up to the point where you can see if it can run continually, unless bad commutatter arcing or some other indication of a fault.

73's de Edd

 

[darren adcock]

You will not be able to turn the motor via the gearbox on the worm drive arrangement.
That's the nature of the worm drive. There are exceptions but I won't go into that.

thanks blue jet

 

[darren adcock]

Sir darren adcock

If you use the adequate powering by a battery, initially with one wire connected, then take the other free one and make a short sweeeeeping on-off temporary contact, just as if you were striking match. If that gives a successful burst of rotation of the motor shaft, try progressively longer temporary power contacts. Up to the point where you can see if it can run continually, unless bad commutatter arcing or some other indication of a fault.

73's de Edd

Will do Edd. Thankyou.

Do people here think 12v at 10a will suffice, or is more ampage needed?

 

[Minder]

Whether it will run on 12vdc OK all depends on the torque demanded by the application.
Load decides torque = current.
The max RPM will also be that much lower.
The automotive battery supply was suggested just for a test, not the permanent supply.
A supply could be as simple as a suitable transformer and a Bridge rectifier, no cap required unless including a PWM control, the ebay ones usually come with the Electrolytic fitted..
M.

 

[darren adcock]

For sure MInder, I thought as much. What I'm working on requires low torque but some other plans will require higher, but again I'll double check the maths with you guys when I need, just started learning algebra so should be able to understand more and not rely so much.

And to be fair, I can affor either a battery or a power supply, that's part of the reason I was resistant to battery solution. But yes, it might be worth having one around for test purposes, I will plan this in for the future.

 

[darren adcock]

Got given a Car battery via a facebook shout out. The motor works fine. Really good to have this battery as a back up and to help rule out a bad power supply or load.

Thanks all for your help

Darren

 

[kellys_eye]

Thanks for the closure....