Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: catnine on July 05, 2011, 05:02:37 pm

Title: When a PT is rated at 100Ma @330-0-330 VDC and has 300-0-300 HT taps
Post by: catnine on July 05, 2011, 05:02:37 pm

 I would then imagine the 300-0-300 VDC HT is less windings and would relate to a less than 100mA rating, is that correct?

 

Title: Re: When a PT is rated at 100Ma @330-0-330 VDC and has 300-0-300 HT taps
Post by: tubeswell on July 05, 2011, 07:50:09 pm

the 100mA rating also applies at the 300V taps

Title: Re: When a PT is rated at 100Ma @330-0-330 VDC and has 300-0-300 HT taps
Post by: kagliostro on July 06, 2011, 12:37:03 am

Voltage is related to the lenght of the winding (more lenght more voltage)

Current ability is related to the thickness of the wire used (more thick more current)

Kagliostro

Title: Re: When a PT is rated at 100Ma @330-0-330 VDC and has 300-0-300 HT taps
Post by: PRR on July 06, 2011, 09:18:56 pm

> less than 100mA

More.

The primary is sized for 330V 100mA; it could stand 300V 110mA.

The 330V 100mA secondary is sized for the losses from 330V worth of winding. Same wire, only 300V in use, about 10% less loss and waste heat. However in 10% less space. But the adjacent space (the unused 30V) is cold.

300V 100mA is conservative and safe.

I'd call it 300V 105mA. But this is really over-thinking. You can always run 20% over rating, with more sag, more heat, less life; or vice-versa 20% under rating. And the difference is small. And you rarely know your current demand that exactly. So 5% one way or the other is "nothing".