Voltage at the load

[EEpowerOK]

A single phase transformer with a 120 volts secondary voltage connected to 500' 250 AWG bare copper in a PVC conduit feeder to a load that draws 40 amps and lags at .85. What is the voltage at the load?

 

[Ship Wreck PE]

Actually with bare copper there will be 0 volts at the load because of short circuit. I am assuming that the distance to the load is 500' and not 250'.

I am getting 119 volts with insulated wires.

 

[RBsai]

i am getting 117.3 volts.

 

[fetaker]

I got VD as 2.65V. And the voltage at load terminal117.35V

 

[EEpowerOK]

120 - 40<-31.8 * ((.052 + j .041)/1000) * 500' = 118.7 volts

 

[EEpowerOK]

Actually with bare copper there will be 0 volts at the load because of short circuit. I am assuming that the distance to the load is 500' and not 250'.

I am getting 119 volts with insulated wires.

Bare copper in PVC conduit so they won't SC, If you use insulated wire then you would have to use the effective Z

 

[RBsai]

Its a single phase, we have to consider return path also (IZ Drop multiplied by 2)

 

[EEpowerOK]

Drop is at the load, one way, does not return

 

[iahim]

For single phase, you do need to include the impedance of the return path, because it affects the voltage at the load. For balanced 3-phase loads, the return path is the neutral, but no current flows through it, so its impedance is ignored.

You probably wanted to say uncoated copper and not bare.

 

[EEpowerOK]

For single phase, you do need to include the impedance of the return path, because it affects the voltage at the load. For balanced 3-phase loads, the return path is the neutral, but no current flows through it, so its impedance is ignored.

You probably wanted to say uncoated copper and not bare.

Yes uncoated copper,

Got that from a CI problem. Don't remember which one.

What about the impedance if asked for the current draw from a single phase load? Is the impedance 2x even though it goes to the load and not back?

 

[iahim]

Are you asking about the impedance of the line or the load? If you are referring to line impedance, yes, for single phase (and dc) you need to double it.

 

[shsweet28]

For single phase, you do need to include the impedance of the return path, because it affects the voltage at the load. For balanced 3-phase loads, the return path is the neutral, but no current flows through it, so its impedance is ignored.

You probably wanted to say uncoated copper and not bare.

Yes uncoated copper,

Got that from a CI problem. Don't remember which one.

What about the impedance if asked for the current draw from a single phase load? Is the impedance 2x even though it goes to the load and not back?

For the single phase situation, the same current going through the phase conductor returns through the neutral conductor, hence 2X the Voltage drop. In the three phase scenario, if loads are balanced then we can assume there is no neutral current and so you only have the voltage drop along the phase.