Voltage Drop Calculation 8

[PoliPoliCarps]

Hello.

I computed my system
From 3.3kV/400V IT System, 50Hz,
Length is 100 mts from Transformer to Main CB of LV Switchgear
Length is 50 mts from Protection Devices to Motor Loads
It calculates the voltage drop but is too high around 17%
Requirement Voltage drop should be atleast 10% only.
I used EPR type of Cable for Mining

Please help me reduce voltage drop

Thank you

 

[waross]

If you want to start multiple large motor together, then forget much of what has been said.
Start by working backwards from the motor loads during starting to the feeders and supply and use appropriately sized equipment all the way back to and including the transformer.
When the transformer is undersized all the calculations in the world will not help.
You must either change the transformer or change your expectations.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Padlock01]

Mr PoliPoliCarps
The excel spreadsheet is for calculating VD at the Transformer terminals (input in Yellow cells)for starting one drive (as well as inputting the other drives kVA as base load.
Waross is correct if you want to start multiple drives at once (which went out with the ARK)then you will have rethink the application. I welcome other members input if they find any anomalies with the spreadsheet.

 

[BlackJackJacques]

I like the spreadsheet and appreciate your sharing. I don't see why for multi starting purposes, the sum of the motors is used, while figures like starting pf, etc is averaged. The result should provide a reasonable reproducible number.

Thanks

JR

 

[Parchie]

Y'all.
Is it just me or I missed a lot here? My calcs do not reflect what is being claimed as "voltage drop" problem on the 400 bus! I see 395V (1%) when all equipment are running!

To say there is a problem when you get a 16% drop when starting is like asking why the sky is blue. It is always like that if you start large motors. It's better to focus on alternative starting methods though.