HT vs LT Motors

The losses in the feeder cables are lower, the lower the current that flows in them, which may be significant for larger loads.

That is why power is transmitted long distances at high voltage and reduced to more manageable voltages at the points of use.

Dear Guest, calculate load current for two motors for two terminal voltage (415V and 6.6KV) you will get answer yourself.

1. 10 KW

2. 1000 KW

Eeerr…. A 1000KW motor is a 1000KW motor, whatever the voltage

415V = 1391A

6.6KV = 87.4A

OK there's the losses to take in to account and additional insulation.

Half efforts gives quarter result,....:)

Do the calculation for 10 KW for two voltage.

This remaining half effort would give 3/4 of result.

You've confused me.

10KW @ 6.6KV = .87A

10KW @ 415V = 14A

Same amount of effort going in ? ? ? ? ?

In addition, you also have at least one less transformer to go through for HT motors. Each one of these has it's own I^2 R losses.

THIS IS THE ENERGY SAVED IN

.REDUCED I(SQUARE)t loss for the motor and the cables as well,and better efficiency as noload losses are less than 1%in HT motors and in LT motor this is around 4%.

Power is power anywhere. The energy loss reduction is % small, but installation and maintanace cost will be significantly different. It is possible that for certain particular instalation the cost will be the same for both sollutions.

For HT equipment and cables are of low corrent capacity but need special cares on insulation and safety.

For LT instalation is simplified, but you will need equipment and cables for high current levels, wich afects safety to.

You have to consider the overall facility needs. Consider energy availability, room space for transformers, cables, safety, manuover possibilitys, and so on.

While higher voltage permits you to use smaller conductors for the same output power, there are other losses that come into play. Higher voltages in AC circuits in crease losses though induction and capacitance.

So you may actually (will?)pay for more kW!

Dear Guest,

For the given Power if the Voltage is high means the Current will be low, as it is inversely proportional. Therefore the I^2xR Lossess will come down, hence the heating effect on the winding will come down.

For Example for 1000 kVA set, for 420 Volts, the Current will be 1099 Amps, and if the Voltage is 11000, the current will be 41.96 Amps. You can calculate the I^2xR Loss.

Further, the Cross Section of the winding of Alternator will come down, hence the size of the Alternator will come down. But the Insulation has to be taken care for 11000 Volts.

DHAYANANDHAN.S., INDIA.

Yes , I agree with KalbBR, there will be more initial investment is required for High Voltage installation. Let me know still there will be saving by using higher voltage Motor/ DG set( 11kV) compare to 415V.