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Some doubts regarding VSDs


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#1 lalmehal

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Posted 04 December 2005 - 09:10 AM

Hello sir,
I am having the following questions regarding VSD pls.clear them.

(1)Can capacitors be installed at output of VFDs ?Why?
(2)Which part of the VSD is most temperature sensitive?
(3)calculations of energy saving with VSDs.

Thank you.

#2 marke

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Posted 22 January 2006 - 09:05 PM

hello lalmehal
1) Capacitors must not be installed on the output of a VSD because the output voltage is made up of a high frequency PWM switching waveform. Connecting a capacitor would result in very high currents into the capacitor which would damage both the capacitor and the VSD.
2) Depends on the design, but as the ambient temperature is increased above 40 degrees C, you need to derate the drive to prevent the power devices from being overheated.
3) Very dependant on the load curve etc.

Best reards,

#3 jraef

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Posted 23 January 2006 - 05:06 PM

Re: Question #1, the real question should be back to you. Why would you want to connect capacitors on the output of a VFD? A VFD will present a .95 power factor to the line, regardless of load on the motor. Why bother with any more capacitors?
"He's not dead, he's just pinin' for the fjords!"




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