48.8 Hp 480 Motor

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Fordean

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Electrical Contractor
The motor load 48 amps 3 phase 440-480
What size breaker and wire should be installed Double checking
Ty
 
Fordean said:
The motor load 48 amps 3 phase 440-480
What size breaker and wire should be installed Double checking
Ty
Click to expand...


Motor OCPD is sized based off of nameplate HP than FLC out of NEC, if your using standard inverse time breaker you can size your breaker up to 250% of the listed FLC I do believe, don’t have a book handy on me.
 
Dsg319 said:
Motor OCPD is sized based off of nameplate HP than FLC out of NEC, if your using standard inverse time breaker you can size your breaker up to 250% of the listed FLC I do believe, don’t have a book handy on me.
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That is how it works with most motors with normal torque characteristics.

If you have one that is not listed in the tables you about have to go with nameplate amps or any manufacturer instructions if there is any that address this.

Fordean, remember you need 125% for conductor so at least a 60 amp conductor.

thermal-magnetic breaker can be up to 250% though often times it can be somewhat less. My square D motor slide calculator says a 100 amp breaker for a 50 HP motor is what they suggest, NEC would allow up to 175 for the 50 HP motor. 250% on 48 amps (with next size higher allowance) should let you go to 125 amps with this 48 amp motor.
 
petersonra said:
wire size and OCPD rating are not based on FLC for normal motors, but on the FLC in the appropriate NEC chart that corresponds to that motor HP.

So what is the motor HP?
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Motor 48.8 hp 440- 480 v 3ph
Feed from 400 amp to 150 amp main (1/0 awg)
3 ph 120/208 to 75 kva trans to
70 amp 480 volt circuit breaker (#4 thhn)
Then 150 feet to exterior 600 volt disc supplying 60 amp pin and sleeve
 
Fordean said:
Motor 48.8 hp 440- 480 v 3ph
Feed from 400 amp to 150 amp main (1/0 awg)
3 ph 120/208 to 75 kva trans to
70 amp 480 volt circuit breaker (#4 thhn)
Then 150 feet to exterior 600 volt disc supplying 60 amp pin and sleeve
Click to expand...
the closest size in the chart would be 50 HP.

the chart says to use 65 A for this size motor.

So the wire would need to have an ampacity of 81.25 A.

The OCPD rating if a CB could not exceed 250% of 81.25 A.

I would question the use of a 150 A CB on the primary of a 208 V primary 75kVA xfmr.
 
petersonra said:
the closest size in the chart would be 50 HP.

the chart says to use 65 A for this size motor.

So the wire would need to have an ampacity of 81.25 A.

The OCPD rating if a CB could not exceed 250% of 81.25 A.

I would question the use of a 150 A CB on the primary of a 208 V primary 75kVA xfmr.
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I have 150 on the 208 side Concerned i undersized breaker with 70 amp
conductors #4 i think are sufficient trying to make sure i do it right before wire cuts
 
75 kVA at 208 V 3 phase is almost 210 Amps. I think a 150 A CB may well hold while the motor is running but it might not hold on startup of the motor or on power up of the transformer.

A 70 A CB feeding the motor is code legal but may trip when the motor starts.
 
Your 460V motor cannot be 48.8HP and have a FLC or 48A.

48.8 is not a standard HP value, it is going to be either 40HP or 50HP. FLC from the NEC on a 40HP motor is 52A, but it's fairly common for the actual nameplate FLA to be lower, so I suspect that you have a 40HP motor with a nameplate that says 48.8 FLA.

Regardless of that, sizing of conductors and OCPDs is done based on the FLC tables in Section 430 in the NEC, usually table 430-150, which is where the 52A comes from. So if it is actually a 40HP motor, your conductors must be rated no LESS than 125% of 52A, = 65A, and the circuit breaker must be no MORE than 250% of 52A = 130A (but next size up can apply).

The only thing you would use the motor nameplate FLA for is in selecting / setting the OL protection in the motor starter.
 
Jraef said:
Your 460V motor cannot be 48.8HP and have a FLC or 48A.

48.8 is not a standard HP value, it is going to be either 40HP or 50HP. FLC from the NEC on a 40HP motor is 52A, but it's fairly common for the actual nameplate FLA to be lower, so I suspect that you have a 40HP motor with a nameplate that says 48.8 FLA.

Regardless of that, sizing of conductors and OCPDs is done based on the FLC tables in Section 430 in the NEC, usually table 430-150, which is where the 52A comes from. So if it is actually a 40HP motor, your conductors must be rated no LESS than 125% of 52A, = 65A, and the circuit breaker must be no MORE than 250% of 52A = 130A (but next size up can apply).

The only thing you would use the motor nameplate FLA for is in selecting / setting the OL protection in the motor starter.
Click to expand...
He posted nameplate of this motor in another thread. Makes no sense to me either but that is what nameplate said. IIRC was also rated 400-480 volts, so probably not built to NEMA standards? Could be errors involved I suppose.
 
Jraef said:
Your 460V motor cannot be 48.8HP and have a FLC or 48A.

48.8 is not a standard HP value, it is going to be either 40HP or 50HP. FLC from the NEC on a 40HP motor is 52A, but it's fairly common for the actual nameplate FLA to be lower, so I suspect that you have a 40HP motor with a nameplate that says 48.8 FLA.

Regardless of that, sizing of conductors and OCPDs is done based on the FLC tables in Section 430 in the NEC, usually table 430-150, which is where the 52A comes from. So if it is actually a 40HP motor, your conductors must be rated no LESS than 125% of 52A, = 65A, and the circuit breaker must be no MORE than 250% of 52A = 130A (but next size up can apply).

The only thing you would use the motor nameplate FLA for is in selecting / setting the OL protection in the motor starter.
Click to expand...
 
This is a cord and plug 8800 psi power washer Used to remove concrete from shoring steel From germany (Karcher )
Its remote exterior I have no motor starter in design Dont believe one is on unit
Unit operates when trigger is pulled on nozzle Little puzzled on this motor operation manual is useless
 
Fordean said:
This is a cord and plug 8800 psi power washer Used to remove concrete from shoring steel From germany (Karcher )
Its remote exterior I have no motor starter in design Dont believe one is on unit
Unit operates when trigger is pulled on nozzle Little puzzled on this motor operation manual is useless
Click to expand...
There is obviously some kind of controller, otherwise it would run anytime there is voltage in supply lines.

Very likely is some sort of OEM motor and is somewhat a one of a kind thing. IDK if they do this with some foreign equipment like they do here but may be no different than some power tools that give a seemingly high horsepower rating. The rating is a peak rating and only for short time. It can not withstand continuous loading at that rating. Other thing though maybe not so likely here is a motor with an increased rating because it is located in an airstream to keep it running cooler. Now if this pressure washer motor happened to be water cooled or something it possibly could have more of a non standard rating I guess.
 
kwired said:
He posted nameplate of this motor in another thread. Makes no sense to me either but that is what nameplate said. IIRC was also rated 400-480 volts, so probably not built to NEMA standards? Could be errors involved I suppose.
Click to expand...
I see that now. it says 440-480V though, not 400-480V.

Still, you can't change physics, they are laws, not suggestions.
When you know HP and want current, it is 1.732 x E x I x EFF x PF / 746. Assuming 480V and .8PF and working backward using the 48A value, the motor would need to be 112.6% efficient... That of course is impossible.

My guess would be that the "48.2HP" number is the typical consumer "marketing BS" HP number, like what people put on compressors and table saws sold at the hardware store. It is the "developed HP" meaning they are calculating the mechanical HP based on when speed drops under a step change in load and the motor goes into Break Down Torque for a second or two. BDT is typically 200%+ of FLT on a Design B motor, so taking that backward on a napkin note, it's more likely a standard 22kW 380V 50Hz motor, which when run at 60Hz becomes 26.4kW, then converted to HP becomes 35.4HP in which case the 48A seems more reasonable.

Bottom line, ignore the HP value on that nameplate, it is "marketing" HP. The 48A is the real value you need to use and from the NEC standpoint, I would use 40HP for sizing the conductors and OCPD.
 
kwired said:
There is obviously some kind of controller, otherwise it would run anytime there is voltage in supply lines.

Very likely is some sort of OEM motor and is somewhat a one of a kind thing. IDK if they do this with some foreign equipment like they do here but may be no different than some power tools that give a seemingly high horsepower rating. The rating is a peak rating and only for short time. It can not withstand continuous loading at that rating. Other thing though maybe not so likely here is a motor with an increased rating because it is located in an airstream to keep it running cooler. Now if this pressure washer motor happened to be water cooled or something it possibly could have more of a non standard rating I guess.
Click to expand...
There is a complete assembly starter and all controllers on unit Just need feeder from new trans One thing i took the label amp and hp off chassis of unit And used that After discussion here I went back to find motor label i had to dismantle machine to get at This label alot different from chassis label
 

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Wow, that's hard to read, but it looks like it is 69.5A FLA? That's a far cry from 48A!

That makes me wonder if they have some sort of VFD integrated into the unit and they are using that to limit the output to 48A, then using that value on their chassis label... very strange way of doing things.
 
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