Fractional HP Motor, LRA

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nvcape

Senior Member
Does anyone know where I can find the starting amps for a 1/6HP, 120V motor. Have about 200 that need to be on a generator. Have found general rules, but not actual data.
 

Ed MacLaren

Senior Member
Re: Fractional HP Motor, LRA

The running current for a general purpose 1/6 HP, 115 volt motor is about 4.5 amps. Starting current could be anywhere from 3 to 6 times running current.
That would depend, among other things, on whether the shaft load is an inertia (flywheel type) load or the type where full load is not applied until the motor is at speed.

I think I would allow 18-20 amps per motor, for those that must start at once.

Ed

[ October 15, 2003, 02:04 PM: Message edited by: Ed MacLaren ]
 

nvcape

Senior Member
Re: Fractional HP Motor, LRA

Thanks Grant and Ed, it sounds safe to say that this is not something I overlooked in a handbook. I called one manufacturer and was told that the torque requirements vary too much for a set value.
 
Re: Fractional HP Motor, LRA

I'm curious how you would size the generator for this application. Are a sizeable number of the motors starting at once?

I don't know what type of generator you're using, but it is detrimental to run diesel gensets for long periods at low loadings (anything less than 70% of rating).

If you are sizing the generator using starting current for 200 motors, seems like your generator would be oversized for the application.
 

nvcape

Senior Member
Re: Fractional HP Motor, LRA

The fans, along with some other items are mandated by the Fire Department. The generator needs to handle the running load and starting loads. I can not step load because of code compliance. If there is a maintenance issue, will need to bring in a load bank for periodic service.
 
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