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 Post subject: VFD modeling ETAP
PostPosted: Sat Mar 20, 2021 8:19 am 

Joined: Sat Nov 07, 2020 10:01 am
Posts: 3
I’m modeling a 200HP output VFD feeding a 200HP pump motor. The ratings from the cut sheet for the VFD are (output max FLA 250A, 160kw, 200HP and input 211A, 175kva) when I input the ratings the load flow calculator fails the VFD but the manufacturer says that the vfd is properly rated for a 200HP motor. I must be doing something incorrect in my model. Does anyone know what I might be doing wrong or any suggestions? Any help would be greatly appreciated.


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 Post subject: Re: VFD modeling ETAP
PostPosted: Mon Mar 22, 2021 11:14 am 
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Joined: Mon Jan 18, 2010 11:35 am
Posts: 526
Location: Wisconsin
PJ wrote:
I’m modeling a 200HP output VFD feeding a 200HP pump motor. The ratings from the cut sheet for the VFD are (output max FLA 250A, 160kw, 200HP and input 211A, 175kva) when I input the ratings the load flow calculator fails the VFD but the manufacturer says that the vfd is properly rated for a 200HP motor. I must be doing something incorrect in my model. Does anyone know what I might be doing wrong or any suggestions? Any help would be greatly appreciated.


How can your output current be greater than your maximum input current?


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 Post subject: Re: VFD modeling ETAP
PostPosted: Tue Mar 23, 2021 7:08 am 
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Joined: Mon Jun 11, 2018 12:02 pm
Posts: 14
Location: Slave Lake, Alberta
JBD wrote:
How can your output current be greater than your maximum input current?


VFD's typically rectify AC to DC, charge large capacitor banks to peak voltage and the use PWM or some version of such to convert back to variable frequency, variable voltage AC thus the output current can be substantially larger if the output voltage to the motor is lower until the charge on the capacitors is drawn down.


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