how to dimension a motor 15Hp 460V 3527rpm?

[charrid]

I am working in a industrial place,. Now i have a job to do and that is : replace a motor ( 2.2 Kw 460V 1770 rpm) for a motor of 15HP 460 V 3572 rpm. this means wiring and protection of the motor.Inclusive the choice of type of calbes?

 

[buzzp]

Seems like quite a change in motors. I can't relally help with cable sizing and feel right about the NEC code so I will leave that one alone. The protection I can help with: I would buy an electronic OL relay with extra protection like Overvoltage, undervoltage, voltage unbalance, under current, current unbalance, single phasing, and reverese phasing. There are several units to choose from. There is one that comes to mind is a model 777 manufactured by SymCom, Inc.

http://www.symcominc.com

I am not a salesman but this unit will give you plenty of protection and allow for expansion later like hooking up communications to talk with a PC or higher level control and also logging of data can be accomplished with this unit. Electronic protection is inexpensive as well. I think this unit sells for $525 and is an UL listed overload relay. Hope this helps.

 

[electricpete]

Changing speed by a factor of 2 is usually NOT an option.

What type of load are you driving (pump, fan, compressor?).
Is the new motor twice as fast or half as fast as the old?

 

[charrid]

first the loaod is to drive a water pump.
the nem one is twice faster as the old one

 

[Takoga]

Looks to me like you have a lot to do on this one.

First off, a 2.2kW motor is approximately 3HP, so when upsizing to a 15HP, your motor starting equipment will also have to be increased. If this is a standard motor starter, you will probably have to go from a NEMA size 0 to a NEMA size 3 (assuming, of course, that you need and want NEMA sized starters). If it is run from a VFD, the size will also need to be increased.

According to NEC Code, all individual motors must have adequate over-current and short-circuit protection. As buzzp pointed out, a properly sized OL relay is necessary. Along with that, you will need to resize your fusing or circuit breaker for the new motor. My guess is that you will need three (3) 40 Amp time-delay fuses or a 45 amp, 3 phase, inverse-time circuit breaker. As far as conductors go, you will need to consult the NEC Code book for the most accurate conductor ampacity ratings but I believe you will probably need to pull no smaller than three #8 AWG THW, THHN-THWN copper wires for this application. Keep in mind that distance, routing and environmental conditions all come in to play when sizing these devices (temperature can have a HUGE impact), so any advice you get here is only for reference. I am not qualified to size any of this on-line!

Before you begin with this, be sure you have the actual name plate data from your new pump motor. That is the data you will actually need properly size your devices.

Hope this helps.

 

[electricpete]

When you drive you pump twice as fast it will draw approximately 8 times the power (assuming no change to the fluid system). Your new motor looks undersized for that.

Also if your pump is designed for 1800rpm it might get very grumpy when you try to drive it at 3600rpm. If the orginal pump was operating near BEP the new pump will be operating way to the left of BEP (assuming same fluid system following typical dp~V-dot^2 type relation) and will vibrate pretty bad. There may be a lot of other hidden effects of suping up that pump speed (cavitation?)... do you have someone looking at that?

Also the pump might not be physically capable of withstanding the increased centrifugal force and bearing loads without destroying itself.

I'm sure you may have considered many of these items already... just wanted to throw in my two cents.