VFD and grid in parallel
VFD and grid in parallel
(OP)
Sirs
The HTLC, a Converteam soft starter that uses VFD technology, permits the running in parallel with the grid before the soft starter be disconnected.
May I do the same using a standard VFD?
The HTLC, a Converteam soft starter that uses VFD technology, permits the running in parallel with the grid before the soft starter be disconnected.
May I do the same using a standard VFD?





RE: VFD and grid in parallel
RE: VFD and grid in parallel
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: VFD and grid in parallel
The HTLC uses basically a MV3000 (VFD) and a special auto-transformer to connect it to the grid?
No smoke escapes.
Where is the magic?
RE: VFD and grid in parallel
RE: VFD and grid in parallel
What is the rationale for this, if I may ask?
RE: VFD and grid in parallel
Bill
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"Why not the best?"
Jimmy Carter
RE: VFD and grid in parallel
By the way, it is also done by several other large reputable manufacturers, Robicon (Siemens) and Allen Bradley are the two I am aware of. It's not that it cannot be done, it's that the economics make it unattractive for off-the-shelf low voltage VFDs that rarely need it.
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RE: VFD and grid in parallel
The HTLC is a short-term equipment just for starting purpose.
My idea of design is to use MV VFDs (2) to start sequentially heavy pumps and keep the last one connected to the VFD to get speed control.Adequate arrangement of VFDs and busbars can provide high flexibility.
RE: VFD and grid in parallel
Also I hope the last started pump that you are controlling speed of is not a running in parallel with the others at full speed (assuming we are talking centrifugal-like pumps). If it is you generally don't get any pumping out of the pump running at lower speed, just a lot of recirculation, vibration, lost energy, possibly damage.
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RE: VFD and grid in parallel
Just make sure you factor in all of the necessary isolation components and consider the issue of servicing one piece of equipment while others continue to run if that's a requirement. The issue there is that vacuum contactors, what are typically used to switch power back and forth, cannot be relied upon as a safety disconnect for equipment servicing. You need isolation switches for that, even if they are not load-break rated.
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RE: VFD and grid in parallel
Still, you cannot parallel inverters if they were not built to be parallelled. It is a sure way to destroy them.
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: VFD and grid in parallel
I am not familiarized with american standards so, my questions are:1.Can a Vacuum circuit breaker at racked-out position and electrically/mechanically locked (for example VD4/ABB Unisafe switchgear) be considered as a safe "disconnect device"? 2.Is it mandatory a grounding switch after the circuit breaker?
RE: VFD and grid in parallel
The components should be considered live until isolated (via racking) and checked and grounded. The grounding can be via a grounding switch or via grounding clamps installed on the bussing.
Depending on the number of pumps in question it can also become an operating and service nightmare. These systems seem simple when just thinking about them but once considering the operation, motor protection and servicing it becomes obvious they are much more complex than a simple starter per motor.
RE: VFD and grid in parallel
I only brought it up because I have seen people do this with non-draw out gear and in that case it would be unsafe unless you have another isolation switch.
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