say a dynamo is 100v and 9.2 amps VA= 920 how much is it in watts, not knowing the power factor
2007-03-29 12:10:09 · 8 answers · asked by Erizu 2 in Science & Mathematics ➔ Engineering
If you don't know the power factor (which represents the ratio between watts and voltamps) you have to assume they are both the same.
For any thing on DC systems that is always true. For a resistive load like a lightbulb on AC that is true. For a motor on AC it is never true since the volts at any instant are not lined up with the amps at that instant so what you multiply turns out to be less power than the VA.
Power companies who have dynamos that make power to sell as VA charge an extra fee for customers with large motors that take a lot of power with low power factor. Those customers need more than their share of those VA to meet their power needs. That forces the customers to attempt to bring their power factor up close to one to avoid that fee.
2007-03-29 12:57:47 · answer #1 · answered by Rich Z 7 · 0⤊ 0⤋
Volt amperes is the unit of measurement of apparent power. Watts is the unit of measurement of usable power or true power. Your dynamo is 920 va. Most generators and dynamos typically operate at 90-95% efficiency. So, on the presumption of 95%, your dynamo has an output of 874 watts.
However, if these figures are actually real measurements, then this is output is true power or 920 watts not volt amperes. The measured 100 volts and 9.2 amps are measurements of true power, so the dynamo probably is 1kva with a power factor of 92% for an output of true power of 920 watts.
2007-03-29 13:33:02 · answer #2 · answered by Anonymous · 2⤊ 0⤋
Power factor will always be .778
Where did this power factor come from?
Answer. On a 60 cycle sine wave, the peak voltage is never used because there is no locomotive force long enough to cause a function on a PC board. 20% less of the sign wave, you have a wider area to work with to offer some sort of extended electron locomotive force. Somehow, it was discovered with a oscilloscope, and a phase shifter, that the maximum use of power was not a peak voltage but at .788 of the sign way.
Mathematically: 920 VA X .778 = 715.76 Watts.
2007-03-29 16:15:59 · answer #3 · answered by John P 2 · 2⤊ 0⤋
Volts times Amps = Watts
2007-03-29 12:13:59 · answer #4 · answered by Anonymous · 0⤊ 0⤋
Va Vs Watts
2017-03-01 05:52:46 · answer #5 · answered by pollmann 4 · 0⤊ 0⤋
Power is voltage times current assuming no phase shift (power factor).
2007-03-29 12:31:17 · answer #6 · answered by Gene 7 · 0⤊ 0⤋
there is ohms regulation and watts regulation. watts regulation is watts = voltagexamperage voltage=watts divided via amperage amperage=watts divided via voltage. you already recognize ohms regulation. the guidelines in no way lie!!!
2016-12-15 11:28:49 · answer #7 · answered by ? 4 · 0⤊ 0⤋
you have to know if it's AC or DC power before you can convert to watts
2007-03-29 12:16:00 · answer #8 · answered by shorty 2 · 0⤊ 0⤋