How to find Horse Power?

Status
Not open for further replies.
Pizza

Pizza

Senior Member
Location
Minnesota
I need to size a motor starter for a motor with name plate ratings of
Voltage : 380V three phase
Watts: 11K
FLA: 22
No hp rating

I believe it's a German motor. It's for a pump that pumps hydronic fluid for hydronic rollers.
I plan on feeding this motor with 480 V.
There is another one of these exact same motors already running on 480v and it runs fine.
Will the voltage increase change the HP?

This other motor is fed directly from a machine control unit and I'm not even sure if it has OL protection. I can't turn the machine off during business hours to look into control unit.

I need to size this motor starter and throw in a disconnect to the motor.
I plan on feeding it with 30 amp circuit.
Now I need a NEMA size ???? Starter.
Thanks


Sent from my iPhone using Tapatalk
 
Pizza said:
I need to size a motor starter for a motor with name plate ratings of
Voltage : 380V three phase
Watts: 11K
FLA: 22
No hp rating

I believe it's a German motor. It's for a pump that pumps hydronic fluid for hydronic rollers.
I plan on feeding this motor with 480 V.
There is another one of these exact same motors already running on 480v and it runs fine.
Will the voltage increase change the HP?

This other motor is fed directly from a machine control unit and I'm not even sure if it has OL protection. I can't turn the machine off during business hours to look into control unit.

I need to size this motor starter and throw in a disconnect to the motor.
I plan on feeding it with 30 amp circuit.
Now I need a NEMA size ???? Starter.
Thanks


Sent from my iPhone using Tapatalk
Click to expand...

If it is not marked with NEMA ratings I don't see how you are going to come up with an appropriately sized NEMA starter.

11 kw is about 15 HP for what that is worth.

I'd suggest an electronic adjustable overload.
 
don_resqcapt19 said:
Is it not going supply more horsepower when run at 60 hertz?
Click to expand...

I'm going to say no. But let's get jraef or golddigger in here to explain in understandable terms why (or to say I'm wrong but I'll put my nickel on the answer).

It's only going to change if the 11kw is going to change by changing the frequency of the input.
 
mgookin said:
I'm going to say no. But let's get jraef or golddigger in here to explain in understandable terms why (or to say I'm wrong but I'll put my nickel on the answer).

It's only going to change if the 11kw is going to change by changing the frequency of the input.
Click to expand...

if it is a centrifugal pump, there is at least some potential that the HP used could increase at a higher frequency.

his other option is some kind of VFD that he sets to limit the output frequency to 50 Hz to match the motor.
 
04a90af6414ef5ec08003a91347dd309.jpg


619e17da9e4f5a2dab69b5fba738210b.jpg



Sent from my iPhone using Tapatalk
 
Just get a NEMA or IEC starter rated for 15HP, @ 480VAC
the amp draw will be less than the name plate FLA Amps so get an electronic overload module, and set it at about 17A on 460VAC
 
Pizza,

Presuming you get the chance to inspect the other running pump, it would be a good idea to check the impeller for size differences, or if a throttling or restricting valve was installed. The motor originally ran on 50 Hz and running it at 60 Hz will be a nominal 17% speed increase. On centrifugal pumps or fans under certain conditions this will mean an approximate 40% more torque to keep the impeller above the new full load speed. One way to solve this problem is to "trim" the impeller, another way is to restrict the output flow (sounds counter intuitive I know). Trimming the impeller is a permanent solution. The restricting or throttling valve can be mis-adjusted by uninformed personnel.
 
How to find Horse Power?

petersonra said:
who knows. the best thing to do might be to see how the other motor is set up but he says he can't.
Click to expand...

This motor assembly was running at a different facility and a non electrician had disconnected it.
Now they moved to a different facility and want to wired now.
From what I got out of the manager is that there used to be a knife style disconnect with fuses in it to control the motor, no overload protection.

The other motor running at the facility I'm guessing has OL protection coming from the control cabinet that feeds the motor




Sent from my iPhone using Tapatalk
 
There are 746 watts per HP. So 11,000W / 746 = 14.74HP

But yes, the HP does in fact increase when the frequency increases, for what that's worth. HP is a shorthand expression of torque at a specific speed. Motor torque is directly related to the ratio of voltage and frequency given to it. A motor designed for 380V 50Hz is the same basic V/Hz ratio as 460V 60Hz, so your motor torque will be the same. But the speed will be 20% faster (60/50). So the HP will increase by 20% to roughly 18HP. Buy a 20HP starter.

By the way, current and torque change together, so since the torque remains the same, the nameplate current will remain the same.

Also, understand that unlike NEMA design motors, IEC motors have no Service Factor, or looked at another way, they are all 1.0 SF.
 
well, my mind is not in this groove, but
11kW @ 480v = ~23A

@ 90% efficiency, 85%PF, 480v, 11kW
single phase ~11.3HP
three phase ~19.6HP
 
151231-0017 EST

Pizza:

Power input to a motor is equal to motor losses plus power required by the load attached to the motor.

Motor loss is noload loss plus I^2*R of the motor windings. Full load will produce maximum resistive loss.

Your load will determine the maximum power input. A 50 Hz motor run on 60 Hz will have an output RPM approximately 6/5 times the 50 Hz RPM. You need to know how your load power requirements vary with load RPM. Other posts have indicated how you could modify this load power.

.
 
FionaZuppa said:
well, my mind is not in this groove, but
11kW @ 480v = ~23A

@ 90% efficiency, 85%PF, 480v, 11kW
single phase ~11.3HP
three phase ~19.6HP
Click to expand...

But the 11kW rating is at 380 volts not 480 volts. The 22 amps mentioned in OP is as you attempted to point out a result of efficiency and power factor.
 
kwired said:
But the 11kW rating is at 380 volts not 480 volts. The 22 amps mentioned in OP is as you attempted to point out a result of efficiency and power factor.
Click to expand...

seems that it is only Watts that matters when looking closer at the electric motor HP equations. 480v@22.9A is the same as 380v@28.9A, =11kW, thus the HP #'s are still the same.

i thought that more amps gives more torque, but in electric its about opposite of engines. with any given input Watts the torque goes up as rpm's go down.

i would still say ~20HP if its 3ph.b

but to note, since the FLA accounts for PF & efficiency, then at 85%PF the efficiency of this motor is near 79%, not 90%, with that adjustment the HP in 3ph is ~16.6HP. i guess the plate might call that a 15hp motor, but i would perhaps use 20hp parts.
 
Last edited:
FionaZuppa said:
seems that it is only Watts that matters when looking closer at the electric motor HP equations. 480v@22.9A is the same as 380v@28.9A, =11kW, thus the HP #'s are still the same.

i thought that more amps gives more torque, but in electric its about opposite of engines. with any given input Watts the torque goes up as rpm's go down.

i would still say ~20HP if its 3ph.b

but to note, since the FLA accounts for PF & efficiency, then at 85%PF the efficiency of this motor is near 79%, not 90%, with that adjustment the HP in 3ph is ~16.6HP. i guess the plate might call that a 15hp motor, but i would perhaps use 20hp parts.
Click to expand...

yeah, with that FLA @380v 3ph the amps are just under the std charts (which extrapolate to 380V@~24A, 460V@21A & 230V@42A).

380V@22A = ~17.2Z(ohm) = 8.3kW
480v/17.2Z(ohm) = 27.9A = 13.3kW <-- i would have to say that the HP output will be greater. i cannot say 480V will damage the motor because the plate could have been stamped for a specific type of application but the actual motor construction might be able to handle the diff.

thats +60% in Watts(FLA).

50 --> 60Hz, you get +20% more rpm's. but i think the major factor is changing from 380V to 460V.
 
Last edited:
...thats +60% in Watts(FLA), which is closer to 20HP than 15HP. in the end i would expect the swap to new V and new Hz to have outcome of ~20HP w/ ~+20% rpm's.
... and i take back my note about HPxTq as rpm's go down, thats for something else.

are there any rpm #'s form the 380V days? compare that to the other motor running @480V ??

... so, some data shows that we look at V/Hz to determine if the motor after can handle the change from 50 --> 60Hz
in this case, its close, the motor will be stressed more

380/50 = 7.6
480/60 = 8

i dunno if that diff has significant impact on the motor.
 
Last edited:
460v would be right on the money. is 460v available? @460v you would get +20% in speed and the HP gets closer to 20, but the V/Hz would be same as 380V@50Hz. the diff with 480V is +5% in V/Hz, probably not enough to damage it as the 2nd one has been ok. question is, long term will it survive? for some reason this motor was designed for V/Hz=7.6

hmmm, ok, it seems that this 7.6 # has a relationship to VFD's.

thats the extent of my contribution here.
 
Last edited:
FionaZuppa said:
460v would be right on the money. is 460v available? @460v you would get +20% in speed and the HP gets closer to 20, but the V/Hz would be same as 380V@50Hz. the diff with 480V is +5% in V/Hz, probably not enough to damage it as the 2nd one has been ok. question is, long term will it survive? for some reason this motor was designed for V/Hz=7.6

hmmm, ok, it seems that this 7.6 # has a relationship to VFD's.

thats the extent of my contribution here.
Click to expand...
460 volts would be the typical nameplate voltage rating of a motor designed to operate on a nominal 480 volt system.

voltage/frequency ratio is important, but you still deliver more power at the higher speed you get because of the higher frequency - if you are driving the same load.

If you are driving the motor's rated load at 380 volts 50 Hz, then by changing to 460 volts 60 Hz and change nothing else about the driven load - you will be overloading the motor.
 
Status
Not open for further replies.
Top