Powering Soft-Start with a VFD
Powering Soft-Start with a VFD
(OP)
I am wondering if anyone knows of any issues that could arise by powering a soft-start with a VFD.
Basically, we need to use the VFD as a phase converter to supply a 3 phase actuator that has SCRs.
Has anyone run into anything like this before?
Basically, we need to use the VFD as a phase converter to supply a 3 phase actuator that has SCRs.
Has anyone run into anything like this before?





RE: Powering Soft-Start with a VFD
RE: Powering Soft-Start with a VFD
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RE: Powering Soft-Start with a VFD
RE: Powering Soft-Start with a VFD
The three tricky parts however, are;
1)You need a good sine wave filter on the output side of the VFD, because the Soft Starters have a line sensing circuit that determines the zero-cross points of the 3 phases in order to set up the gate firing sequence. Non-sinusoidal outputs can confuse them.
2) You need to have a contactor on the output of the VFD that only closes when the VFD is at full frequency, otherwise the Soft starter is getting low frequency to the gate firing control board and that can mess you up as well (but it depends on the soft starter).
3) You need to power up the soft starter control circuitry from the LINE SIDE of the AC supply, before the VFD. But on some soft starters, this may interfere with proper operation because they may have a system that detects line loss if there is control power but no line power. If that's the case, then the control circuit power needs to be interlocked through an aux of the same contactor mentioned above.
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RE: Powering Soft-Start with a VFD
Keith Cress
kcress - http://www.flaminsystems.com
RE: Powering Soft-Start with a VFD
"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: Powering Soft-Start with a VFD
Keith Cress
kcress - http://www.flaminsystems.com
RE: Powering Soft-Start with a VFD
RE: Powering Soft-Start with a VFD
Keith Cress
kcress - http://www.flaminsystems.com
RE: Powering Soft-Start with a VFD
"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