Factors Effecting Motor rating for LV/MV system
Factors Effecting Motor rating for LV/MV system
(OP)
Hi,
Normally at each plant we had both medium voltage & low voltage motors. The low voltage or medium voltage distinction is based upon kW rating of motors. I am interested to know the factors which identifies the maximum size of motor (kW) is suitable for a particular system voltage.
Thanks in advance
Normally at each plant we had both medium voltage & low voltage motors. The low voltage or medium voltage distinction is based upon kW rating of motors. I am interested to know the factors which identifies the maximum size of motor (kW) is suitable for a particular system voltage.
Thanks in advance





RE: Factors Effecting Motor rating for LV/MV system
As an example I once studied the economic impact of 830 V distribution for a grass roots refinery! The savings was formidable. But it was rejected... the real problem being the ego's of those who object to "change"!
RE: Factors Effecting Motor rating for LV/MV system
Robert W. Smeaton "Switchgear and Control Handbook," 2nd Edition, McGraw-Hill Book Co., 1987, page 9-9, Table 3b
provides the HPs versus motor rated voltages.
RE: Factors Effecting Motor rating for LV/MV system
Reference IEEE Std 141-1993 Recommended Practice for Electric Power Distribution for Industrial Plants [Red Book] Table 3-11 Standard Voltages and Preferred Horsepower Limits for Polyphase Induction Motors
RE: Factors Effecting Motor rating for LV/MV system
I want to confirm, for making the LV/MV distiction based upon kW rating, is power distribution system of the plant play any role?
RE: Factors Effecting Motor rating for LV/MV system
- The total connected load
- Availability of power supply, LT/HT
- The cost of LT/HT switchgear
- Permissible voltage drop
- Cost of HT/LT motor
- Efficiency of motors
- Repair facility available in & around
- Cost of Energy
Considering all the factors , for a very large system of app. 250 MW & 22000 motors, it was found that the optimum rating is 415 V ac for <200 kW,6.6kV for > 200 kW & 3MW for 11 kV.
However specific calculation is to be made considering the factors.
RE: Factors Effecting Motor rating for LV/MV system