Brake Generator

Hi Pinku,

Starting a 320kW motor DOL is not a very good idea!

You need some form of soft starting and I would recommend for your application to use star delta starting, if you set the star delta starter up correctly you will limit the star startup current to about 2 x full load current, but the secret is the transition from star to delta should be at a time when the motor has reached the maximum speed and the current has started to level of, as this will reduce the time that when switched to delta (6 x full load current) that the motor has to run at over current to get up to full speed.

The way you were starting the motor DOL would have created about 3300 amps per phase that is more than enough to trip a 1600 amp circuit breaker.

I am not sure on what you mean by an air brake generator, I will look for other comments to this thread.

Best Regards

Joe

look we have our air seperation plant (capacity 420tpd) here we use turbine coupled with brake generator for reaching the cryogenic temp for our products

so what i wanted to clear earlier that

this brake generator is of 320 KW and run by an ACB of 1600A but that meant for producing power and feed to our system bus(415V) so when will this start producing power and feed our system bus and how to monitor that

You need to explain you're self better.

I appreciate English is probably not your first language but I can't grasp what you're trying to do.

If it's a generator it will be rated either as star or delta and will need synchronising before the breaker closes. If it's a motor starting as star / delta then you need to look at the starting arrangements.

It's unclear if you're referring either a motor or generator.

Where this set up fits in to your process isn't of concern to us, we need basic facts.

Was the ACB and starter recommended or selected by motor manufacturer?. What are the type/settings of OC/SC protection on ACB

1) Whats the basic concept around using brake generator in air separation plants?

You have answered it yourself at #3. It is basically to make-up cold losses at cryogenic temp.

2) Whats the sequence of operation of starting this brake generator?

In fact starting the brake generator is considered as ASU is stared. Make sure that Main Air Compressor is started, system is slowly pressurised, refrigeration unit (if you have) is started. Now, go to turbine and see that its oil system is on (check oil pressure and oil temp), open inlet and outlet valves and slowly open its inlet nozzles (or capacity control mechanism). Keep eye on speed, you can observe that speed is increasing. Control in such a way that rate of increase in speed is neither too slow nor too fast. Allow to reach to brake-in speed (around 1480 or 2960 rpm depending on no. of poles in generator). Brake-in point can be easily recognised by a big sound. Once it is brake-in, it starts as a motor, but once it crosses 1500/3000 rpm it will switch over automatically as generator.

3) What I want to confirm when will the motoring will stop and generating will start?

Please see above.