Calculating motor amperage by useing resistance
- Thread starter nathan1
- Start date
- Status
- Location
- Massachusetts
Re: Calculating motor amperage by useing resistance
I do not believe you can determine motor current from the winding resistance that easily.
A motor running with no load draws less current than a motor driving a full load.
The current changes even though the windings have not.
I believe it would be like trying to determine the current draw on a transformer by the resistance of the windings without knowing the load current.
I do not believe you can determine motor current from the winding resistance that easily.
A motor running with no load draws less current than a motor driving a full load.
The current changes even though the windings have not.
I believe it would be like trying to determine the current draw on a transformer by the resistance of the windings without knowing the load current.
- Location
- Massachusetts
Re: Calculating motor amperage by useing resistance
Just curious to why you would want to do this?
The Tables in the end of 430 will give you a close idea of the amperage if you know the voltage and HP.
Just curious to why you would want to do this?
The Tables in the end of 430 will give you a close idea of the amperage if you know the voltage and HP.
jimwalker
Senior Member
- Location
- TAMPA FLORIDA
Re: Calculating motor amperage by useing resistance
Other than trying to see if any windings have shorted,i see no value in ohms on a motor.Has nothing to do with amps
Other than trying to see if any windings have shorted,i see no value in ohms on a motor.Has nothing to do with amps
Re: Calculating motor amperage by useing resistance
No real reason...inmy career so far I havent gotten too far with motors unfortunatly, just saw one sitting there at the shop one day...it had all the information on it and I had my meter. I was just going to check my ohms law seemed e divided by r isnt always true so I thought I had better find out why. Thanks for all the feedback all the same.
No real reason...inmy career so far I havent gotten too far with motors unfortunatly, just saw one sitting there at the shop one day...it had all the information on it and I had my meter. I was just going to check my ohms law seemed e divided by r isnt always true so I thought I had better find out why. Thanks for all the feedback all the same.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: Calculating motor amperage by useing resistance
A motor is not a resistive load. At a dead stop the motor is a short circuit and as it comes up to speed it becomes a generator, developing back EMF. this emf opposes the current. As the motor slows down, the back emf increases, current goes up, work increases to meet the load (within limits)
A motor is not a resistive load. At a dead stop the motor is a short circuit and as it comes up to speed it becomes a generator, developing back EMF. this emf opposes the current. As the motor slows down, the back emf increases, current goes up, work increases to meet the load (within limits)
- Status