# Primary current vs. BPS

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• Subject: Primary current vs. BPS
• From: "Tesla list" <tesla@xxxxxxxxxx>
• Date: Tue, 14 Jun 2005 22:20:18 -0600
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`Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>`

`Hi All,`

While playing with the ScanTesla program, I realized I might have been making a mistake over the years.

I think I always assumed that primary RMS current was directly proportional to the BPS rate. So if you double the BPS, the primary RMS current doubles...
So if you have 10Arms at 120 BPS you would have 20Arms at 240 BPS.

`But that is not true.`

`To double the RMS current you have to have four times the BPS rate or:`

`Ipri : sqrt(BPS)`

`Thus, at 240 BPS the current above would be 14.142 Arms.`

If you double the BPS you double the power. But power is proportional to I "squared", not I. Therefor, to double the power, you only need to increase the current buy sqrt(2)...

Doubling the BPS rate doubles the power which implies that the RMS current goes up by a factor of 1 / sqrt(2)....

`I may have been the only one making this error, but now I stand corrected *:-)`

The next version of ScanTesla will have a factor of 1 / (sqrt(BPS)) for a way to find Ipri(rms) independently of already knowing BPS or the calculation interval in the program's RMS calculation....

For the MMC calculations, I seem to have done it right. So I probably forgot it and had to relearn it 0:-p

`Cheers,`

`	Terry`