Voltage Drop for 400 Hz System

[charlie b]

Anybody know how a VD calculation might change, when you are dealing with 400 Hz? I know that inductive reactance increases and capacitive reactance decreases, with an increase in frequency. But does that significantly alter the voltage drop along feeder or branch circuit wiring, or is it a second order effect?

We are adding a third hangar to a facility. The 400 Hz inverter has spare capacity, but we are concerned about the distance from the inverter to the new hangar. Can I use the same Excel spreadsheet that I use for 60 Hz VD calculations, and simply disregard the effect of the higher frequency? Or is there a separate equation that I need to bring to the party?

 

[GoldDigger]

Anybody know how a VD calculation might change, when you are dealing with 400 Hz? I know that inductive reactance increases and capacitive reactance decreases, with an increase in frequency. But does that significantly alter the voltage drop along feeder or branch circuit wiring, or is it a second order effect?

We are adding a third hangar to a facility. The 400 Hz inverter has spare capacity, but we are concerned about the distance from the inverter to the new hangar. Can I use the same Excel spreadsheet that I use for 60 Hz VD calculations, and simply disregard the effect of the higher frequency? Or is there a separate equation that I need to bring to the party?

The major difference, from what I have seen, is that for very large wire sizes the skin effect will be more important. This effect causes alternating current to flow more near the surface of a wire than in the core and so the resistance will be higher then the area of the conductor would predict. There are tables which show impedance (still mostly resistive) as a function of frequency.

In addition, the inductive effects of things like running individual phase wires through separate openings in ferrous metal sheet will be much more critical. Capacitive coupling effects will also be 7 times greater, so keeping wires close together and also interchanging positions of wires (twisting) becomes a bigger concern.

 

[Hv&Lv]

I had that question also when working on aircraft generators. I have found some formulas, one being Volt.drop= cable length x loadcurrent x(cable resistance R x cosphi + reactive resistance XL x sinphi) / sqrt3.
Here is a calculator we have been using, you just need to convert to mm.

 

[petersonra]

the larger the wire the worse it is.

 

[ghostbuster]

We had a situation where the moulded case breakers would trip at lower current levels when connected to 400 hz. power.(higher order 400 base harmonics were the problem)

 

[bob]

http://ecmweb.com/training/electrical_basics/conductor_resistance_basics_0301/

 

[charlie b]

Here is a calculator we have been using, you just need to convert to mm.

Was there supposed to be an imbedded link to a web site with a calculation process? If so, I don't see the link.

 

[Besoeker]

the larger the wire the worse it is.

I'd be interested to know where you got that page from.....it's astonishingly like this one:

 

[Besoeker]

There are tables which show impedance (still mostly resistive) as a function of frequency.

Actually, for the conductors I cited in the other thread the inductance goes from being less than resistance at normal mains frequency to being being four times it for the smaller conductor and seven times it for the larger.

In addition, the inductive effects of things like running individual phase wires through separate openings in ferrous metal sheet will be much more critical.

Does anybody do that at ANY frequency?

 

[GoldDigger]

Actually, for the conductors I cited in the other thread the inductance goes from being less than resistance at normal mains frequency to being being four times it for the smaller conductor and seven times it for the larger.

The inductance will not change with frequency, but the inductive reactance certainly will! The importance of the reactive component in the VD on the operation of loads will also depend on he power factor of the load. (There is a great long thread on that around here somewhere.)

Does anybody do that at ANY frequency?

They should not, but they may have been able to get away with it operationally at 60Hz if the inspector did not notice. They will have big problems at higher frequencies with the same bad installation.
Other induced current and magnetic field effects like running the cable through a closed steel mounting strap will also be worse.

 

[Besoeker]

The inductance will not change with frequency, but the inductive reactance certainly will! .

Yes, sloppy of me. But you knew what I meant.