bus duct between transformer and frequency converter
bus duct between transformer and frequency converter
(OP)
Hello,
I would like to learn your opinion on the folllowing.
We have a frequency converter (VFD) for a machine drive application (VFD rated power is approximately 20 MW).
The frequency converter is fed by a transformer converter outdoor located. Teansformer primary voltage is 33 kV.
The transformer is a multi-winding phase shifting transformers for 36 pulse VFD/transformer topology at input. Transformer turn ratio is 1 to 18 (quite high).
The current design is based on bus duct connection between frequency converter and its transformer. The bus duct shall cover distance of less than 30 feet.
The question is what is your experience on this type of connection (bus duct) given the high turn ratio transformer and resulting high number of connections between transformer secondary and VFD ? are there any technical limitations or issues you could identify?
Any orientation is appreciated. I can try and provide complement of information as you would require.
I would like to learn your opinion on the folllowing.
We have a frequency converter (VFD) for a machine drive application (VFD rated power is approximately 20 MW).
The frequency converter is fed by a transformer converter outdoor located. Teansformer primary voltage is 33 kV.
The transformer is a multi-winding phase shifting transformers for 36 pulse VFD/transformer topology at input. Transformer turn ratio is 1 to 18 (quite high).
The current design is based on bus duct connection between frequency converter and its transformer. The bus duct shall cover distance of less than 30 feet.
The question is what is your experience on this type of connection (bus duct) given the high turn ratio transformer and resulting high number of connections between transformer secondary and VFD ? are there any technical limitations or issues you could identify?
Any orientation is appreciated. I can try and provide complement of information as you would require.






RE: bus duct between transformer and frequency converter
Thanks
RE: bus duct between transformer and frequency converter
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: bus duct between transformer and frequency converter
bus duct was specified primarily on reliability ground.
When you mention that you don't know of anyone who does this, what is the principal reason / technical limitation for them not doing this with a 18:1 and 36 pulse topology? Risk of failure of the connection (mechanical failure such as bending problem, overheating of bus bar, etc) ?
Are there any concern on safety later on being this a quite big power rating?
I will check anyway all the voltage and power I've given are correct;
RE: bus duct between transformer and frequency converter
The transformer primary side is 11 kV and the transformer is rated 15 MVA. The other info are unchanged.
Appreciate if someone can help me on the issue ?
"If you want to acquire a knowledge or skill, read a book and practice the skill".
RE: bus duct between transformer and frequency converter
I think if would be difficult (if not impossible) to have hard bus connections to all of those connection points in the VFD power modules, so you will likely end up with cable from the ends of the bus bars to the rectifier inputs anyway. All you are doing then is exchanging longer wires for shorter wires and adding another connection in each one, which increases the possible failure risk.
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: bus duct between transformer and frequency converter
The rating at the drive is 5.0 kV. Think the topology is not H drive in my case but old fashion topology (based on power cells). Possibly the number of connectors are about half of what you described but still this remains a lot.
Looking at your picture, the transformer and drive are at same location / nearby. In the case I am concern with, the transformer will be located externally.
Agree with you that most likely the problem is how to fit all the bus bar connections to the power module which normally is a quite compact thing with small dimensions like in your picture - so if at all feasible, it will be crowded and dense.
What I still can't figure out, is the failure mode which can be involved. I mean when you fit so many connections I guess you do need some special or custom made design. In this case and in your opinion, what would make the failure risk higher when compared to a cable type approach of connection ?
"If you want to acquire a knowledge or skill, read a book and practice the skill".
RE: bus duct between transformer and frequency converter
Are you attempting to locate the transformer outside so as to avoid the heat rejection? If so, the two times I have proposed this have resulted in the cost to make it work being so extreme that it was untenable.
Have you already purchased the drive in question" There are alternatives that could give you similar performance as far as harmonic mitigation, but without the multi-pulse transformer. That way you can use a standard transformer and standard bus duct.
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington