transformer specs such as DCR and etc: how does it affect voltage on the secondary?

[jarthel]

I found this transformer in RS.

Here's the datasheet: http://img392.imageshack.us/my.php?i...titled2oa6.png

I'm wondering how does that affect the voltage on the secondary.

Thanks for the help

[lndm]

Imagine this resistance as a resistor in series with the winding. Voltage will be dropped on this resistor, depending on the current drawn, and can be calculated in the usual way.

In cases where the current drawn is fairly constant, such as with single ended circuits, there is little to worry about apart from the small loss of voltage. Generally speaking, class AB stages tend to perform better when the source resistance is as low as practical.

[jarthel]

Originally posted by lndm
Imagine this resistance as a resistor in series with the winding. Voltage will be dropped on this resistor, depending on the current drawn, and can be calculated in the usual way.

In cases where the current drawn is fairly constant, such as with single ended circuits, there is little to worry about apart from the small loss of voltage. Generally speaking, class AB stages tend to perform better when the source resistance is as low as practical.

I understand the voltage loss due to DCR. but how about specs such as regulation/iron loss?

Thank you.

[poobah]

I do not see the the full VA rating. But, 84% efficiency and 10% (or so) regulation would not be considered impressive or even typical. It is true that smaller transformers are generally less efficient than their bigger brothers... this is really only because of manufacturing economies.

For example, a big mains trans for a building might have 98-99% efficiency.

You can do better. Efficiency is not the main issue, but regulation can be depending on the nature of your load.

[jarthel]

it's rated 50VA.

[lndm]

Here is some info you may find useful

http://www.siteswithstyle.com/VoltSe...PSU_NOTES.html

[poobah]

Jathel,

The efficiency sounds about right for a little guy... I guess.

The questions would be then:

1) are you using it at full rating, and will it deliver the required secondary voltage?

2) is your load constant? If so, then regulation becomes less important.

[jarthel]

Originally posted by poobah
Jathel,

The efficiency sounds about right for a little guy... I guess.

The questions would be then:

1) are you using it at full rating, and will it deliver the required secondary voltage?

2) is your load constant? If so, then regulation becomes less important.

1. no. I won't use full rating. I will parallel the 2 9V secondary to get 9@5.5A but will only be using 2.55A.

2. load is fairly constant. the load will be tube heaters so it'll be just like have resistors as load at the end.

[poobah]

You're fine then...

Also paralleling the secondaries will reduce the effective resistance by 1/2... it's a good thing.

[jarthel]

Originally posted by poobah
You're fine then...

Also paralleling the secondaries will reduce the effective resistance by 1/2... it's a good thing.

I would then use a low-voltage drop regulator (LT1084) between the 1st cap and the load. still enough?

simulation (using simetrix or switchercad)says it will be enough if I do get the 9V or more on the secondaries.