There are a number of energy saving schemes for induction motors on the market today.
Some are based on Power factor correction and incorrectly state a savings in KWHrs. There will be a saving in KVA and KVArs, but the motor will draw the same KW for a given shaft load.
Another scheme is based on the NASA algorithm proposed by Frank Nola. This scheme reduces the voltage applied to the motor when the motor is running with reduced efficiency and can reduce the iron loss in the motor at very light loads. This is only of benefit with small motors with excessive iron loss that run for extended periods of time at no load.
The third scheme that is currently promoted, is the use of a variable speed drive. This is primarily useful in reducing the losses in the driven load rather than the motor itself, and in some cases, due to the harmonics drawn from the supply, and the losses in the inverter, can increase the running costs of the installation.
There are savings to be made, but be careful and fully engineer your application. You can only save energy that you are wasting, and only from where it is wasted.
I have a paper on the energy savers using the NASA system at
cbarn24050,sorry for the partial enquiry I asked.
I am now very interested in such energy saving product and want to get more information from here,especially those about power factor.have I made me understood clearly this time?
---------------------------
Marke,thanks for your kind assistance. you've helped me a lot.furthermore,would you like to tell me more about the principle about power factor correction?
Power factor is the ratio between KW and KVA and gives an indication of the "usefulness" of the current. A power factor of 1 shows all current is generating KW and doing work. A power factor of 0 indicates that no KW and therfore no work is done. A poor power factor means that a higher current is flowing in the supply than is doing useful work and this results in increased losses in the supply, and increased loading on supply transformers. A poor power factor can be because of inductive or capacitive current, and/or because of harmonic currents.
for more information see
Suggestion: If there are harmonics present, then there are two different power factors:
1. One is related to the fundamental waves of voltage and current. It is called the displacement power factor.
2. Other is related to the total power in watts over total volt-amperes. This means that the total volt-amperes have to include harmonics.
