Voltage correspond to min. voltage

[etflava]

Hi all,


This is the situation. I have been asked to find the voltage correspond to the minimum speed permanent magnet generator. The generator is 75 kw, 3 ph, 0.8 PF and it is using variable speed engine as a prime mover. This generator is supposed run a motor (40 HP, 460/3Ph/60Hz) and my supervisor is interested to know the current drawn when the voltage out put is minimum which is correspond to the minim speed of the generator. I contacted the generator manufacturer but they need to know what s/n of the generator which I am waiting to get in couple of days.

So I was wondering if any of you guys can give me some guidelines in this situation.

Thanks and appreciate all your comment.

k.

 

[davidbeach]

Try it.

 

[itsmoked]

How can you run 40 HP, 460/3Ph/60Hz motor with a variable speed generator? Yes, yes I know there are ways, but I want to hear The Plan...

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[rbulsara]

I would think speed affects the frequency and not the voltage. Voltate is proportional to field excitation.

So is this generator a substitute for a VFD? A dedicated generator for one load?

Like Keith, I am interested in this novell idea too. What is the benefit?

 

[etflava]

First of all thanks for the replies I have so far. Well I am not very sure how the whole system works am just in the process of learning how everything fits together. This is just my first project I have involved since I finished school and for some reason I am a bit confused with the whole thing. But according to my supervisor, since the generator is driven by a variable engine he is interested to know the voltage correspond to the mini. Speed. The reason being, he just want to make sure that there will be no over heating due to the higher current that might result from this lower voltage. By the way, the motor will be used for cooler.

One more thing, I was also been asked to look for a start for this motor. So what do you guys suggest in the type of start I should go for. I am thinking about suggesting the Direct-on-line (DOL).

My last question will be, what will b the suitable formula to use to find the current that the motor will draw.

I don’t know if I give you guys enough information yet but I hope it u understood it and get more feed back soon.

Thanks again.

K.

 

[rbulsara]

Thats a loaded request to learn a lot.

Google search "motor starting" or "motor starters" etc and get try to learn from them.

Grab some basic books for electrical motor controls and synchronous generators etc.

Oh by the way, look for another job rather than work for this outfit, if you want to excel in engineering.

 

[waross]

At 75 KW I suspect that even though the engine is variable speed the governor will keep the actual speed during normal operation between 1850 RPM and 1800 RPM.
The permanent magnet generator probably refers to the excitation system rather than the generator itself.
Does the nameplate on the generator indicate any speed other than synchronous speed? (1800 or 1200)
Does the name plate indicate any frequency other than 60HZ.?
Please post the information when you get it.
I may be wrong. If so, I and several others are in for a learning experience. It has happened before.
BTW Keith. The purpose of UFRO is to unload a momentarily overloaded set and give the prime mover a chance to recover, and to avoid Automatic Voltage Regulator burnout at low speed/frequencies. It ramps the voltage down as the frequency drops (starting at about 57Hz. or 58Hz).
This has become a standard feature of AVRs on sets this size.
I wonder if the Under Frequency Roll Off circuit is capable of operating continuously rather than only for momentary overloads and prime mover starting.
respectfully