Electrolytic vs Oil Filled Capacitors

[drktmplr12]

I have some concerns regarding allowing electrolytic capacitors for DC link, as opposed to oil filled. Other than life expectancy, what are inherent advantages or disadvantages to a medium I voltage (4.16kV) drive? Are the maintenance tasks and/or costs of replacing either similar?

 

[Besoeker]

I have some concerns regarding allowing electrolytic capacitors for DC link, as opposed to oil filled. Other than life expectancy, what are inherent advantages or disadvantages to a medium I voltage (4.16kV) drive? Are the maintenance tasks and/or costs of replacing either similar?

Electrolytic caps give you far more uF for your Buck and have a much smaller footprint.
Typically we used 3,300uF 450V Icar units. Several hundred in some cases for the banks in larger drives.

 

[drktmplr12]

Electrolytic caps give you far more uF for your Buck and have a much smaller footprint.
Typically we used 3,300uF 450V Icar units. Several hundred in some cases for the banks in larger drives.

okay so they are cheaper and smaller. are they half as expensive as oil filled equivalents?

this particular drive is the Siemens GH180. Anyone have history with them?

 

[Besoeker]

okay so they are cheaper and smaller. are they half as expensive as oil filled equivalents?

A fraction of the cost per uF. But they are different beasts for different jobs.

 

[winnie]

We use Semikron SKiiP modules, which come with the capacitors. They have changed from using electrolytic caps as standard to using film caps.

This is for 700V DC link. I don't know how operating at the MV level changes the math of selecting capacitor type.

-Jon

 

[GoldDigger]

We use Semikron SKiiP modules, which come with the capacitors. They have changed from using electrolytic caps as standard to using film caps.

This is for 700V DC link. I don't know how operating at the MV level changes the math of selecting capacitor type.

-Jon

The electrolytic capacitor uses a chemical film on the surface of one plate as the insulator. At some point you reach the feasible breakdown voltage limit of that film and have to go to putting capacitors in series (maybe with an appropriate balancing network) to achieve your required voltage. Plastic film and paper insulated capacitors can simply increase the insulation thickness to increase rated voltage.

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