208v question

[mivey]

Based on the last post does all of this mean the "Oregon Fudge Factor" only applies to a Delta not a Wye 208/120 configuration?

Also someone stated Sin 30 deg, I believe it is COS 30deg to calculate the phase angle..

I have heard this phrase before but have never been interested enough to look up what they were talking about. It appears to be some play on the difference between phase current and line current, maybe based on a test someone took or something. I'll leave that investigation up to you as Roger's diagram covers the delta nicely and doesn't get into some play on words that may lead to confusion.

In the delta system, the current flowing in the line is the sqrt(3) times larger than the current flowing in the transformer coils. The line to neutral point voltage is sqrt(3) less than the coil voltage. The line-line voltage is the same as the coil voltage.

In the wye, the line and coil current is the same. The line-neutral point current is the same as the coil current. The line-line voltage is sqrt(3) times larger than the coil voltage.

sqrt(3) / 2 = cos(30) so:
120 * sqrt(3) = 207.8
240 * sqrt(3) / 2 = 207.8
240 * cos(30) = 207.8

2 / sqrt(3) = 1.1547 and 2 / sqrt(3) = 1 / cos(30) so:
207.8 / sqrt(3) = 120
207.8 * 2 / sqrt(3) = 240
207.8 * 1.1547 = 240
207.8 / cos(30) = 240
240 / 1.1547 = 207.8
240 * cos(30) = 207.8

No need to play games with the numbers, it is just math.

 

[rattus]

Based on the last post does all of this mean the "Oregon Fudge Factor" only applies to a Delta not a Wye 208/120 configuration?

Also someone stated Sin 30 deg, I believe it is COS 30deg to calculate the phase angle..

Consider a single phase, 208V service.(2 legs of a wye) with a 10A line to line load. What is the apparent power?

Is it 2 x 120V x 10A = 2400VA?

or is it, 208V x 10A = 2080VA?

The ratio is 1.154 = 1/cos(30)

This is the gist of a question on the Oregon Supervisor's Test.