Motor Starting Study

[buckeyemurphy]

I am doing a motor starting study and with Full Voltage start I am getting around a 12% drop at the bus. I want to do a reduced voltage start with series reactance, could someone give me some assistance on how to go about sizing the reactor to reduce the voltage drop.

Thanks

 

[jraef]

Size the reator to fit your garbage can, and use a solid state starter. That way you can adjust the settings to whatever you need to work in your application.

"Venditori de oleum-vipera non vigere excordis populi"

 

[ScottyUK]

Hi jraef,

That would depend on the voltage and motor size which the OP really should have posted first time around if he wants any proper advice. I certainly agree with you that for an LV motor a solid-state soft starter is likely to be cheaper and give much more flexibility than a reactor. A big motor on an MV system might be a different story. It would certainly need a big garbage can for an MV reactor!



----------------------------------

If we learn from our mistakes,
I'm getting a great education!

 

[jraef]

LOL, OK I'll give you that!

But seriously, even Medium Voltage RVSS starters have come down in price enough to be condidered against electro-mech RV starters. They are still slightly more expensive, but provide significant other benefits that would be costly to duplicate in the alternatives, such as full adjustability, smaller footprint, built in motor protection functions and deceleration control for pumps. The last project I compared pricing on, a 700HP 4160V pump motor, had only a 5% installed cost price premium with all the features needed in both systems. The RV Reactor starters were cheaper in base price, but needed Multilin 369's to match the protection requirements, all of which were built-in to the RVSS starters. Add to that the ability to decel the motor for pump control and the 5% was worth it.

Once the size goes above 400A (2500HP 4160V), RVSS starters are usually LESS expensive than electro-mech., a commonly missed fact because the applications are fewer and farther between.

"Venditori de oleum-vipera non vigere excordis populi"

 

[MVRockwell]

buckeyemurphy,

I would still suggest you look at an autotransformer starter. I know this may seem like old technology, but with a 12% voltage drop solid-state soft-starters start hitting their effective limits. When it comes to getting the smallest system voltage drop and still start your motor, an autotransformer is still better. I'm not saying a solid state won't work, but if your main consider is system voltage impact, an autotransformer will still out perform, regardless who's soft-starter you purchase.

 

[buckeyemurphy]

Sorry, I should have shown the data for the motor and the voltage to be used at. 2500HP motor, 13.2KV. How do I go about getting an ohmic value reactor size to be used for reduced voltage start?

 

[Bung]

What sort of pull-out capability is required? Inserting series impedance is not going to work to well if the motor isn't going to be able to get away. And can the motor handle it (extended run-up = extra heating, etc)? Motors that size are usually quite finely designed, so you may have to be careful how you treat it.


Bung
Life is non-linear...