Parallel combination of VSD
Parallel combination of VSD
(OP)
Hi,
We need to install one 1500 amps @ 400 V variable speed drive for a variable torque application.
We have two options in hand-one with two 700 amps VSD in a parallel combination that is two single VSD units in parallel sharing a common DC bus.
The other option is a standard one with a main rectifying unit,one DC bus and a main inverter module.
I have no basic experience of parallel drives and, as technical support is miles away, I would be pleased to have inputs from forum members.
Bob
We need to install one 1500 amps @ 400 V variable speed drive for a variable torque application.
We have two options in hand-one with two 700 amps VSD in a parallel combination that is two single VSD units in parallel sharing a common DC bus.
The other option is a standard one with a main rectifying unit,one DC bus and a main inverter module.
I have no basic experience of parallel drives and, as technical support is miles away, I would be pleased to have inputs from forum members.
Bob





RE: Parallel combination of VSD
Output reactors will be good for you so that static and dynamic load sharing is OK. Paralleling has some advantages - and disadvantages. Advantages are that you have two smaller units and that you (if load permits) sometimes can run with reduced load if one of the inverter sections fails. Keeping spares for two smaller units sometimes is cheaper than for one big unit. It depends on what IGBT are used. Disadvantages are that most people are less familiar with such inverters and that the might be a psychologic "wall" to break.
Gunnar Englund
www.gke.org
RE: Parallel combination of VSD
A project I worked on a year or three ago deliberately sequenced four parallel switching modules so they switched in quadrature, thus raising the ripple frequency of the combined bank four-fold and allowing a much smaller switching filter to be used. Obviously they had to be synchronised, but there was no requirement for coindicident switching: indeed this would have defeated our intent completely. The bank was part of a fairly large (MW-level) active harmonic filter built for a water company who were upsetting their DNO with massive harmonic pollution. A number of banks were ganged to provide the required power rating.
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RE: Parallel combination of VSD
Gunnar Englund
www.gke.org
RE: Parallel combination of VSD
Even if one use double-winding motors, one can experience problems if there is no phase-angle between the two windings or if there is not enough inductance before the common coupling. Been there :)
My advice; ask your vendor for good references.
torslum