Current Source Invertor VDS

[dithomas]

Does anyone have experience with Current Source Invertor VDS?

 

Any comments on the pros and cons when compared to PWM VDS?

 

Dan

[marke]

Hello dithomas

 

Current source inverters used to be more common than they are now. They are commonly used with inverters employing GTOs ( now days higher voltage) and have the advantage of lower fault current which means that the GTOs or thyristors are retained within the controlable range.

I think that the advantages for PWM outweigh the current source when IGBT switching devices are used.

Are you looking at new equipement?

 

Best regards,

[dithomas]

Hi Marke,

 

Not being an AC drive expert, I am researching all of the options for my UPS+VFD+Positive displacement Pump+very long motor lead application.

 

I have read resent information on the benefits of CSI drive with regards to low current %TDD imposed on the UPS at 100% speed which could allow for a smaller UPS rating and the apparent elimination of dv/dt issues allowing for the use of regular motor leads and a standard motor.

 

Since this application has to do with the normal and emergency operation of a piece of critical equipment in a generating station the most economical solution is the not highest priority.

 

I have read many threads on this and many other forums leading me to believe that there are many risks associated with the combination of the PWM UPS, the PWM VDS and long motor leads. Due to the environment, the motor will be remote from the VFD in the magnitude of hundreds of feet.

 

I have been in contact with a manufacture here in the USA that has done a lot of work in CSI technology primarily for wind power applications. Some resent studies seem to back-up the benefits.

 

Just wondering about the down sides other than a cost disadvantage at the 480VAC level.

 

Dan

[marke]

Hi Dan

 

The lower harmonic input is a plus, and yes, I would expect a greater tolerence to long motor cables to be a plus also. The cost would be a definite negative and it may be cheaper to use a standard PWM with appropriate input and ouput filtering. You would need to research that one.

I suppose my major concern would be that CSI inverters are not common so you will be locked in to one supplier, and in 5 years time where are you?? At least with a PWM drive, you will always find a replacement, may be different, but it will be there. Not so sure about the CSI though.

 

Best regards,

[dithomas]

Hi Mark,

 

You are correct about the long term availablility and the lack of suppliers. The one supplier here is a 4 year old start-up company.

 

I have looked at output filters; one called a 2k - 8K sine wave filter and an other called a dv/dt filter. Do these filters have different applications?

 

I also read about an input passive matrix filter.

 

The output of the PWM UPS has a built in filter.

 

Dan