# NCEES Power 114



## Gnana (Aug 27, 2010)

Can anyone shed any more light why the motor voltage is thesame as that of the dc link other than the explanation offered in the book? I am still not getting it.

Thanks


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## cableguy (Aug 28, 2010)

OK, well I'll give it a go.

Don't think of them as "transistors"... since they're operating as an ideal switch, think of them as contacts for a relay. Ignore the BJT transistor look and draw in an open relay contact... -||-

Let's call the "transistors"

A B C

D E F

Then we have legs 1, 2, and 3 of the motor.

Close A and E. You now have 679 volts between legs 1 and 2.

Open A and E and close B and F. Now you have 679 volts between legs 2 and 3.

And round it goes...

Does that help?


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## Gnana (Aug 30, 2010)

Thanks Cableguy!! I think i got a better hang of it now.


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