VFD as a power supply frequency converter
VFD as a power supply frequency converter
(OP)
Dear all,
we have a machine 70 kW designed for 400 V 50 Hz which has to be
installed on a 380 V 60 Hz system. Voltage is ok, it is within the design range, but the mechanics does not allow a change in frequency and we cannot modify the electric panel. So I' ve searched on Internet for frequency converters and I've found two types: one done with motors and one static. I've asked a price for a static one but it looked expensive to me, so I asked an offer for an inverter same power (90 kW to have a safety margin for async motors starting)and the price is less than the half.
I can understand why:
a) the inverter is manufactured on a large scale
b) the static converter has an isolation transformer at the output plus filters to give out a good sine wave, not a PWM
Am I missing something important? thank you in advance for your advice.
we have a machine 70 kW designed for 400 V 50 Hz which has to be
installed on a 380 V 60 Hz system. Voltage is ok, it is within the design range, but the mechanics does not allow a change in frequency and we cannot modify the electric panel. So I' ve searched on Internet for frequency converters and I've found two types: one done with motors and one static. I've asked a price for a static one but it looked expensive to me, so I asked an offer for an inverter same power (90 kW to have a safety margin for async motors starting)and the price is less than the half.
I can understand why:
a) the inverter is manufactured on a large scale
b) the static converter has an isolation transformer at the output plus filters to give out a good sine wave, not a PWM
Am I missing something important? thank you in advance for your advice.





RE: VFD as a power supply frequency converter
David Castor
www.cvoes.com
RE: VFD as a power supply frequency converter
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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RE: VFD as a power supply frequency converter
RE: VFD as a power supply frequency converter
You probably need to look harder. I can probably think of a manufacturer or two who still make a system, in that power range, that doesn't use PWM, but it would be a struggle. The same goes for the output transformer.
Most of the UPS systems, in this power range, have the facility to take 60 HZ in and output 50 Hz. They will all (OK, nearly all) be transformer less and utilise PWM as their switching mode. They are going to be way more expensive than a standard drive but as others have stated it depends upon what your load is whether a drive is suitable or a decent sine wave output is required.
RE: VFD as a power supply frequency converter
RE: VFD as a power supply frequency converter
Bill
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"Why not the best?"
Jimmy Carter
RE: VFD as a power supply frequency converter
Thank you again
RE: VFD as a power supply frequency converter
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: VFD as a power supply frequency converter
RE: VFD as a power supply frequency converter
RE: VFD as a power supply frequency converter
RE: VFD as a power supply frequency converter
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