Robicon Power Cell pre-charge circuit?
Robicon Power Cell pre-charge circuit?
(OP)
I was told that the Robicon Gen 3 power cells do not use a pre-charge circuit for the DC Bus and they actually use the high impedance of their special pahse shifting, multi tap tansformer. Can anyone confirm or deny this? if so it will be the first VSD that I have seen to not use a pre-charge circit (resistor/swicth) to prevent high inrush currents upon powering up the dc bus capacitors.





RE: Robicon Power Cell pre-charge circuit?
Maybe someone else could confirm/deny this.
RE: Robicon Power Cell pre-charge circuit?
As to Robicon's design, that has been around for quite a while now. As was explained to me, the drawback (if you want to call it that) is that the drive and transformer must be matched, thus sold together and be in the same cabinet. Other drive mfrs can have the transformer mounted separately, i.e. outside of the building to reduce the heat load inside. Robicon's take on that is that you need ventilation for the drive anyway, so having the transformer inside is not that big of a difference in exchange for the payoff of not having a precharge circuit.
RE: Robicon Power Cell pre-charge circuit?
I had told them to check the precharge resistor. They couldn't find it, so I had to go there and show them. Took me eight hours of driving to get there and same time to come home again.
No wonder they couldn't find the resistor. This drive had a thyristor controlled mains rectifier (not a true AFE) and the precharge was done same way as Robicon, using commutating reactor impedance and thyristor delay angle taken up gradually to charge the capacitors smoothly.
It is not uncommon. The actual drive was from 1989. So the technology has been used for a long time.
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Robicon Power Cell pre-charge circuit?
This drive I am talking about is 6600V / 2000HP but as we know Robicon uses low voltage (690Volts)cells in series and phase shifted to make up the medium volatge.
Thanks again for all of your input.
RE: Robicon Power Cell pre-charge circuit?
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Robicon Power Cell pre-charge circuit?
RE: Robicon Power Cell pre-charge circuit?
My statement about the SCR front end was not directly related to your question about the Robicon design, but rather a confirmation of DickDV's response as it related to LV (Low Voltage) drive, which is what the AB 1336 drive is. It was meant to point out that there are a lot of different topologies out there.
Robicon's system does indeed use the high impedance of their matched transformer in their design, that's one of the reasons the transformer is integral to the drive.
With CSI drives, the motor and the drive must be matched for similar reasons. That is why people have tended to shift away from using CSI technology. It does make the drive somewhat bullet proof however; I always liked that aspect. I once worked on a 2300V drive in a pump station that had flooded. We cleaned out the muck, put all the PC boards through a dishwasher, dried everything out and it fired back up. I seriously doubt a PWM drive would stand up to that kind of abuse.
RE: Robicon Power Cell pre-charge circuit?
RE: Robicon Power Cell pre-charge circuit?
RE: Robicon Power Cell pre-charge circuit?
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Robicon Power Cell pre-charge circuit?
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com