DC Bus modeling in SKM
DC Bus modeling in SKM
(OP)
Hello
Could somebody tell me how to model a DC bus in SKM.
The system i have right now is AC rectified to DC and inverted to AC back again running 10-12 motors.
The inverters are fed from the DC bus, I am trying to find out the short circuit current available at the DC bus also taking the capacitors in the inverters into effect.
I am aware of the industry standard which says that capacitors can be neglected, but in my case i have 42 drives each with 6 caps of 5600 micro farad. I believe this would make difference to the short circuit at the DC bus. I cannot find a way to model this stuff. I have also attached a picture of the setup
Any help would be appreciated.
Thanks!!
Could somebody tell me how to model a DC bus in SKM.
The system i have right now is AC rectified to DC and inverted to AC back again running 10-12 motors.
The inverters are fed from the DC bus, I am trying to find out the short circuit current available at the DC bus also taking the capacitors in the inverters into effect.
I am aware of the industry standard which says that capacitors can be neglected, but in my case i have 42 drives each with 6 caps of 5600 micro farad. I believe this would make difference to the short circuit at the DC bus. I cannot find a way to model this stuff. I have also attached a picture of the setup
Any help would be appreciated.
Thanks!!





RE: DC Bus modeling in SKM
RE: DC Bus modeling in SKM
RE: DC Bus modeling in SKM
RE: DC Bus modeling in SKM
Good value for the money, around USD 1k for the entry level system, which is what I use.
http://www.gke.org/pub/files/AC%20sixpulse%20recti...
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: DC Bus modeling in SKM
I'm not familiar with SKM, but FWIW I agree that the capacitors will have an effect.
If you're modelling your short circuit as a fixed (low) resistance, then I think you'll get fairly accurate results using superposition. Use SKM to model the fault current due to the AC sources, then add in the discharge current of the capacitors: I = (Vbus / R) * e ^ (-t/RC)
For R, add the short circuit resistance, the average series resistance of the DC bus between the caps and the fault location, and the series/parallel combination of the ESR of the bus caps.
RE: DC Bus modeling in SKM
I will try to calculate it by hand and see how the results are going to look.
@Skogsgurra-Looked at PSIM simulator online, looks interesting. but i don't think this has the ability to run different kinds of studies like the short ckt, harmonic, load flow, etc etc..
but i think this is a good software for simualtions
RE: DC Bus modeling in SKM
RE: DC Bus modeling in SKM
IF so, simple: E=.5*c*v^2
so why not just add up all ur c (in farads), stick in formula with v (volts) of your dc bus, and calculate the energy stored there?
RE: DC Bus modeling in SKM
RE: DC Bus modeling in SKM
SKM Power Tools is not an electrical transient analysis modeling program. It basically models steady-state conditions for short-circuits and power flows. It has a transient motor starting analysis, but that is not the same thing at all.
Determine capacitor contributions for faults is problematic due to the high-frequency ringing of the capacitor current that typically occurs.
RE: DC Bus modeling in SKM
Bill
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"Why not the best?"
Jimmy Carter
RE: DC Bus modeling in SKM
@Waross--attached find the rough sketch