PT ratings

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syn

Well-known member
Joined
Oct 11, 2005
Messages
653
Hi
  I have a couple of questions regarding PT secondary ratings. Is there any reason not to use a 40V transformer for a +48V power? After the bridge it is going to be ~56VDC so plenty of a margin left for  regulator to regulate. Same question for heater  PT ratings, 7VAC should be enough (~10VDC after the bridge)
and again ~3V margin left for the regulator to do its job?
Thank you
 
syn said:
7VAC should be enough (~10VDC after the bridge)

Only if your rectifier has zero Volt forward drop.

But if you have a 7VAC winding, why not power the heaters directly from it? If you're concerned about the 10% overvoltage just insert a resistor.

JD 'KISS' B.

EDIT: Typo
 
Thank you jdbakker. It is a PCB job so I want DC to power the heaters.
 
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