ghostlymoron
Well-Known Member
I've had a 24v bilge pump kicking around in my shed for ages. I've just measured the resistance across it which is 1.17kohms. Is that ok or duff?
Electrical Resistance of bilge pump
- Thread starter ghostlymoron
- Start date
rogerthebodger
Well-Known Member
DC motors are inductive machines do will have a low dc resistance. This only shows that it is not duff through one of it windings.
It could be duff through any of its other windings.
I have a dc gear pump that has one of its windings open circuit but all the others are OK and it runs but it it stops with the open circuit next to the brushed it will not start until I give the motor a spin then it goes OK.
Put 24 vdc on a see if it runs.
ghostlymoron
Well-Known Member
I haven't got easy access to 24v so thought I'd try the easy thing first.
lw395
Well-Known Member
If it's a simple brushed motor, 1.17k ohms is duff. That would be a stall current of 20.5mA.
But not all bilge pumps are simple brushed motors....
But not all bilge pumps are simple brushed motors....
rogerthebodger
Well-Known Member
Sorry I missed the k, yes that is duff.
LadyInBed
Well-Known Member
If it's been neglected for some time high resistance contacts wouldn't surprise me.
Give the motor a good clean, check the connections then apply some voltage, you never know your luck!
Give the motor a good clean, check the connections then apply some voltage, you never know your luck!
William_H
Well-Known Member
A 24v bilge pump should run slowly on 12v for a test. Actually not that much slower because at lower speed less back EMF so more current so power will be less but not as much as say with a light bulb. ol'will
PS back emf is the internal voltage generated by a motor when running which tends to oppose the supply voltage so reduces current when rotating at speed. No rotation no back emf so high input current. Motor up to speed current falls. Current falls so motor slows so it comes to a happy settled RPM until load is applied when speed falls so current increases. Hence power of a 24v motor on 12v is much more than the 1/4 that ohms law might suggest.
PS back emf is the internal voltage generated by a motor when running which tends to oppose the supply voltage so reduces current when rotating at speed. No rotation no back emf so high input current. Motor up to speed current falls. Current falls so motor slows so it comes to a happy settled RPM until load is applied when speed falls so current increases. Hence power of a 24v motor on 12v is much more than the 1/4 that ohms law might suggest.
ghostlymoron
Well-Known Member
I binned it after post 5.
LadyInBed
Well-Known Member
In the recycle bin I hope
lw395
Well-Known Member
Let's hope it wasn't a perfectly good brushless motor...