Any Internation or rule of thumb to decide the motor shall run with LV or MV. 1

[Michael2009]

Hi Sir,

Did we have any international guideline or rule of thumb to determine the motor shall power by LV or MV.
I am struggle to make decision. I have a project motor size is 200HP. And LV voltage is 380V 3phase 50Hz. I am thinking to go for MV system 6.6kV...
Any standard guide telling how many HP or Kw motor shall be operate in MV ?

Thanks.

 

[panter]

2009,
Power of MV motor should be same and similar torque characteristics like LV motor in your project .
We have couple motors on 6.3 kV sistem which are 200 kW output power .
If you have opportunity to purchase MV motor of 200 HP and estimates that additional equipment will not be too costly decision is yours .
Good luck

 

[itsmoked]

Consider the staff support available. Do they have 6.6kV skill?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LionelHutz]

No, there is not. The choice largely depends on local power availability and support capability factors.

 

[waross]

Generally a higher voltage is not considered until the HP exceeds the normally available voltage.
Then a number of factors are considered:
Is the higher voltage available on site or will new transformers and switchgear be needed?
How long will the feeders be? As conductor up sizing for voltage drop increases for longer feeders, a higher voltage becomes more attractive.
Do you have tradesment familiar with and certified to work on the higher voltage?
Compare the costs of an installation at the normal plant voltage and at the higher voltage.
A secondary concern is safety compliance and the added cost of compliance at the higher voltage, wich brings us back to the first concern.
The main concern is cost.
Even after consideration, many motors may still be connected at the lower voltage. As the HP/voltage ratio gets higher, more installations will become feasible at the higher voltage.
An option that I have seen used is to have a service contract with a firm that has the skills and certification to work with the higher voltage.
One application that I remember was a commercial site with 4160 Volts incoming and utilization at 208 Volts. A 600 HP compressor was supplied directly from the 4160 Volt system. Our firm was contracted to do all service work on the 600 HP motor.
200 HP at 380 Volts may not be economically feasible at 6.6 kV.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[edison123]

200 HP is a borderline case between LV and 3.3 KV. As others have said, it all depends on your system capability (handling large starting current in LV would be one, system voltage dip at such a start would be another) and system design. 6.6 KV seems overkill unless your present system is 6.6 KV.

Muthu

http://www.edison.co.in

 

[ScottyUK]

I agree with Edison, if you had 3.3kV available then the jump to the higher voltage would be around 150kW - 200kW, depending on how robust your LV system is. A 200kW motor starting will cause a noticeable dip even on a big LV transformer (2.5MVA - 3MVA), and the problem just gets worse as the transformer gets smaller. If your choice is limited to either LV or 6.6kV then I would say you'd make the jump to the higher voltage at a larger rating than 200HP, more likely around 300HP - 350HP or so.

 

[7anoter4]

First of all I agree with waross: there are a lot of parameters to take into
considerations and mainly the transformer rated power and the distance from
the transformer to motor location.
IEC 60034-1 ch. 5.7 Co-ordination of voltages and outputs states:
It is not practical to build machines of all ratings for all rated voltages. In general, for a.c. machines, based on design and manufacturing considerations, preferred voltage ratings above 1 kV in terms of rated output are as shown in Table 1.
Table 1 – Preferred voltage ratings
Rated voltage Minimum rated output
kV kW (or kVA)
1,0 < UN ≤ 3,0 100
3,0 < UN ≤ 6,0 150
6,0 < UN ≤ 11,0 800
11,0 < UN ≤ 15,0 2,500
However,400/415 V induction motor of up to 500 HP [4 poles] it is a standard rated output at many induction motor manufacturers

 

[unclebob]

Are you planning to use soft-starters or drives? These babies are important factors to consider too.

Got a customer who is using 350 HP motors for pumps at 600V with 18 pulses drives.