Recent content by asekhar

"when there is a power demand is there the existence of some electromechanical reaction forces which make the stator (rotor) more difficult to turn.".... Answer is Yes. depending on the power demand, the energy required to turn the turbine at the same speed is more. The turbine / engine...

I have not seen any such factor put for generators to account for number of starts. Basically because in case of generators, the starting does not give it any serious thermal shock. I have experience with power generation from 12 MW upto 110 MW machines, & in none of them the vendors have...

Could be the lug is not fitted properly or the termination surface is uneven causing insufficient contact. Anand Sekhar

raynh tem1234 has already responded on your query.. the second stage ONAF switches on more fans to provide still higher cooling. Anand Sekhar

Must be ratings with different means of cooling... minimum with ONAN, middle with ONAF, & highest with OFAF. ONAN - Oil Natural Air Natural ONAF - Oil Natural Air Forced OFAF - Oil Forced Air Forced Anand Sekhar

FAQ237-1224: Motors: Changing between a 50 and 60Hz supply, gives detailed analysis of this. You would require to derate it for power & voltage to avoid cooling issues. Additionaly probably you will need to find out the critical speed of the motor, incase it falls near the new rpm (in this...

I am not sure what you are asking. If it is how a meggar testing is done, I have explained below. Meggar is basically measurement of insulation resistance of the machine. The meggar leads are to be connected between the terminal & earth and the readings noted. Obviously, it is done with the...

The maximum rated motor that the generator can start will depend on many factors. What is the base load? What is the generator AVR droop characteristic? Since you mention 650% starting current, I assume that you are only considering DOL start, if you use other means of starting, you will be...

The motor should not be operated at 575 Volts. If the motor is designed for 460 volts, that is the voltage at which it should be run. VFD is a variable frequency drive, which will vary the frequency of the supply so that the speed of the drive can be changed, as CJCPE explained above. Hope it si...

I firmly believe that a combination of both SW & HW interlock is the better option. All emergency / critical interlocks should have hardwired backup, while interlocks of lesser criticality can be just SW interlock. Anand Sekhar

Hi Slava, I know that system capacitive currents exist & will depend on the size of the system & lenght of its cable network. The capacitive contibution is calculated & used for setting of earth fault protection alarm / directional earth fault protection trip for unearthed systems. But I am...

Ungrounded system will not have earth fault current. Anand Sekhar

jraef, My understanding of glowz's requirement is that he needs a bypass to take the contigency of soft start failure. To take care of the contigency of soft start failure, I think it is essential to isolate the softstarter. The bypass which you have mentioned is basically the energy saving...

Rohra, I do not think that the VFD would be having a Auto changeover to bypass, it must be manual changeover. Anand Sekhar Power Systems Consultant

What I understand is that your customer wants a provision to do DOL start incase of softstarter failure. Is the motor rated for a DOL start & is the power system designed to support DOL start? That is the first issue which needs to be established. Incase both the above requirements are okay...