voltage drop

[gashman63]

Running a 40hp motor for a fire pump. Source is 800 feet away. Source is 240v delta. installed 240 to 208/120 transformer. When motor starts, voltage drops from 208 phase to phase to 150. Ran parallel 350 and still drops. Just for a second. Correction?

 

[GoldDigger]

Did you measure the voltage drop at the transformer for reference?
Is the motor designed for
208 volt operation?


Tapatalk!

 

[ActionDave]

How much drop? Is the motor coming up to speed ok? What is the voltage when the motor is running?

It would be expected for voltage to drop for a moment on startup.

 

[ptonsparky]

Why did you lower the voltage ? You should have raised it to 480.
Where did you put the transformer? At source? 800' away?
What size transformer did you use? The impedance of an added transformer will increase the voltage drop.
What is the VD at the source when the motor is started?

I use a quick voltage drop calculator for sizing wires that gives a rough calc for irrigation systems.
800' with a 40 HP load:

480v = #2AL
240v = 2/0 AL
208v = 3/0 AL

Your 350s should be more than adequate for the load.

 

[ptonsparky]

You could put a Power Factor Correction capacitor at the load but that isn't your problem.
Start at the POCO transformer and go from there. Does the POCO know what you have for load?

We are putting in a 75 HP 480v motor at 1000' and will use one set of 250 AL.