Bridgeport motor ID

joe_m said:
Are you running it off of the static phase controller and trying to determine what the horsepower of the motor is? If so, I don't think that is something you can measure correctly that way.
If you absolutely can't live without knowing the horsepower then maybe put an ad on CL asking for someone with a rotary phase controller (which theoretically provides 100% 3-phase power) or a shop with real 3-phase power and see what they'd charge for 10 minutes of their time for you to take the motor to them to power it up at 100% and then measure the amps drawn the way explained above.

If you're going to keep fiddling around with it in your shop though, are you measuring like this:

power panel wired somehow (directly or through plug) to the static phase controller.
static phase controller has three wires coming out to those three paired wires on the motor.
two of the wires go directly to the motor.
one of the wires gets connected to one of the wires on your multimeter and the other wire on the multimeter goes to the motor.

And of course to make sure you don't burn out, blow up or destroy your meter/self/shop: there should be a setting on your multimeter to measure amps instead of voltage. You gotta set it to the amps, and you have to choose a max amperage higher than you can expect to hit with that motor.

Good luck.
Be Safe.

Joe
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Joe,
you have some excellent points, thanks for the input.
i have one disagreement, you can accurately determine the working hp of the motor provided you are able to get an amp reading and a voltage reading. if it runs, you can measure volts multiply them by amps and divide by 746, you get hp.
make sense?
mike:))
 
i would like to make an important point of clarification....
we are trying to determine the WORKING HP of a motor to rate for a VFD.
we are not trying to find the RATED HP of the motor, that calculation is irrelevant in this case.
mike:))
 
Ulma Doctor said:
Joe,
i have one disagreement, you can accurately determine the working hp of the motor provided you are able to get an amp reading and a voltage reading. if it runs, you can measure volts multiply them by amps and divide by 746, you get hp.
make sense?
mike:))
Click to expand...

I freely admit I'm not an electrician - so of course there's a 99.999999999999999999999% chance I'm wrong.:)) But the motor in question is currently being powered by a static phase controller that is only providing 2/3 the power it normally pulls. If/when he buys a VFD it will be running on all three legs. Right now the motor isn't working at full capacity. It spins, it provides some power to the mill, but deep down inside it's saying to itself "sheesh, why won't this guy put out a few bucks for a rpc or vfd so I can stretch this 3rd leg and really show him what I'm capable of doing." So sure we can measure what amps it's pulling off the static phase controller, but don't we have to do some fuzzy math to account for the future when the motor is getting all the juice it wants? :dunno:

Joe
 
WooHoo got it. Got ahold of a clamp meter. wire to 1,7 reads 2.38a. same for 3,9. I didn't read the 2,8 pair, but I can. What about the fact that it is not running on all three legs? I read everywhere that you lose 1/3 hp this way. Does that figure into your figures?
 
I went ahead and read that one just in case, it came up 0.0.
 
Ok, if I have this right. V x A = W. W/746 = HP. 240 x 2.4 = 576. 576/746 = .772. Would that be right? .772 hp. If so I'm just guessing it would run closer to 1hp on a vfd?
 
Yes, it looks like it is a 3/4hp motor so it would run fine on a 1hp vfd in which case you could get the one with the reverse button for about $200 and not have to worry about wiring in the drum switch. Or you could get the one without the reverse switch for less, you just have to decide if you're going to power it with 110 or 220 and if you want a dial or just pushbuttons.

Joe
 
LEEQ said:
Ok, if I have this right. V x A = W. W/746 = HP. 240 x 2.4 = 576. 576/746 = .772. Would that be right? .772 hp. If so I'm just guessing it would run closer to 1hp on a vfd?
Click to expand...
i would do the same thing on another leg just to check yourself if you checked A, then check leg B or vise versa.
then whichever working HP is higher, use that figue to rate your VFD.
does this make sense?
mike:))
 
joe_m said:
I freely admit I'm not an electrician - so of course there's a 99.999999999999999999999% chance I'm wrong.:)) But the motor in question is currently being powered by a static phase controller that is only providing 2/3 the power it normally pulls. If/when he buys a VFD it will be running on all three legs. Right now the motor isn't working at full capacity. It spins, it provides some power to the mill, but deep down inside it's saying to itself "sheesh, why won't this guy put out a few bucks for a rpc or vfd so I can stretch this 3rd leg and really show him what I'm capable of doing." So sure we can measure what amps it's pulling off the static phase controller, but don't we have to do some fuzzy math to account for the future when the motor is getting all the juice it wants? :dunno:

Joe
Click to expand...
Joe,
what you have incorrectly assumed that his static phase converter does anything other than start the 3 phase motor, some types will add dc current to the circuit, yes i said dc current, to raise the voltage in the generated leg should the voltage fall below a predetermined or sometimes adjustable value, to balance the phase in periods of high demand. but it is merely a motor starter...
once the three phase motor starts, his unit will have little to do with the operational circuit of the motor.

2/3 power is just another assumed value, an operating 3 phase motor will generate the third leg of power with or without a static converter being present, provided 2 legs of power are supplied without interruption.
granted, the third power leg is generated at a cost to the motor but not 1/3 of it's power output...
by your logic his motor that had measured a no load of .77 hp would be if your logic held true to be .66 hp.
as you see 1/3 is not lost, a little less than 1/4 on the leg that was tested no load.

there is no argument with installing a VFD, were just trying to rate his VFD.
mike:))
 
phase o matic advertises 2/3 of hp.
the 2/3 is due to a safety factor in their computations for start up.
the motor will perform better than rating after the motor is running.
mike:))
 
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