# Power system design problem

1. Nov 22, 2006

### khamoshie

Im currently working on a university assignment and am quite confused in the following design problem..........

Assume that a new in a facility 3 new plants are being setup. 2 of these plants have all motors rated at 50 hz while the third one has all motors operating at 60 hz. the first two plants require electrical power of around 40 MW and the 60 hz plant requires 6 MW. Which would be a better solution for the configuration of power generation...

(1) Setting up two suitably rated generators one that generates output at 50 Hz for the 50 hz plant and the other one generates output @ 60hz for the other plant...

(2) Or Setting up a single generator of 50 Hz and all motors of the 60 hz plant to be connected via VFD's...

note :Standard LV voltage @ 50hz is 400V p-p
All motors in the 60 Hz plant (180 total) operating at 480V p-p ,60hz

My Understanding of this problem is that exactly what would be the impact of using so many VFD's in the Plant.........

Any help would be highly Appreciated....

2. Nov 23, 2006

### NoTime

Looks like you need to work out the costs for each configuration.
Do you need VFD for each motor?
Can you use one for the entire plant?

3. Nov 23, 2006

### khamoshie

Yes Cost may be a factor but the initial concern is the reliability of the system design.....I mean using a single 50 hz generator will simplify the power generation system but at the same time it will also introduce more maintenance cost for the VFD's....

And if we do it the other way, this would simply mean that there would be a dedicated generator for the 60 hz system....no VFD's would be required but now the power generation will be at two different frequencies.....

Simpy if we initially disregard the cost overheads what would be a better Engineering design.......?

4. Nov 24, 2006

### NoTime

You have to chose your design constraints.
If not cost, then you get into MTBF for generators vs VFD
or conversin effiency.