I need to test inverters that are normally driven by three phase PMA (permanent magnet alternator). Laboratory 3 phase output supplies are mighty spendy for what I really want to use them for in a factroy floor test.
Anybody out there tried filtering the PWM output on a VFD motor drive to see if it can be sine wave like or at least "unspiky"?
Thanks much, Ed V.
You don't have 3-phase power available? Maybe you just need a transformer.
Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
What a coincidence! I just ran acoss a Microchip app note last night dealing with that very topic!
Good luck, Ed, and have fun!
Tom
I have 3 phase power but I need it to be around 160 to 200 VAC. 3 phase variacs are kind of pricey also particularly if you want to talk to it(rs232).
Thanks, Ed V.
There's one on eBay now with a current bit of $25 and $20 domestic US shipping. I wonder if the bidder noticed it's a 400Hz type.
Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
I have been involved in the use of both custom and commercial sine filters for VFDs. Good ones usually cost about as much as the drive. Here is an example of a commercial brand.
There are 3-phase sine wave inverters, but they are probably more expensive again.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
That is one pricey filter. It actually costs a little bit less to have a 3 phase drive run a custom built motor generator of the same power than use the same drive with the filter. Now of course I have to wonder if I need the filter to protect the motor. : ) We currently use what our vendor is supplying ofr filtering.
Thanks much, Ed V.
EdV ed snipped-for-privacy@my-deja.com posted to sci.electronics.design:
Maybe not, if you buy the motor and a VFD from the same source they are on the hook for it working. Filtering above and beyond what they use may be irrelevant. The filter that is going to matter is the harmonic filter between the source and the VFD.
Have you told us how much power is involved?
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