failing low-voltage dimmer

[Jungle Jim]

hi all,
i have some 600VA low-voltage dimmers being used with a 120VAC/24VAC
magnetic transformer. this transformer is rated for 450 Watts. a
unique feature of the transformer is a boost tap which adds in 0.5V
increments to the output AC; i.e. if the output was 23VAC - which
could cause problems for the 24VAC lights - then the transformer
could be setup for two boosts.

the loads are 24V cove lights which have drawn as much as 350 Watts
from the transformer.

back on the primary side, it is the dimmers that have been failing.
the measured amps from the dimmers is only around 3 Watts.

1) could the 350 Watts on the secondary side of the transformer equate
into more than 600VA for the dimmer on the primary?

2) could in-rush current be a problem with a setup like this?

3) could the boost-tap be causing extra impedence on the primary?

thanks for any help you can provide!

brother jb

 

[PhattyMo]

Jungle Jim wrote:

hi all,
i have some 600VA low-voltage dimmers being used with a 120VAC/24VAC
magnetic transformer. this transformer is rated for 450 Watts. a
unique feature of the transformer is a boost tap which adds in 0.5V
increments to the output AC; i.e. if the output was 23VAC - which
could cause problems for the 24VAC lights - then the transformer
could be setup for two boosts.

the loads are 24V cove lights which have drawn as much as 350 Watts
from the transformer.

back on the primary side, it is the dimmers that have been failing.
the measured amps from the dimmers is only around 3 Watts.

1) could the 350 Watts on the secondary side of the transformer equate
into more than 600VA for the dimmer on the primary?

2) could in-rush current be a problem with a setup like this?

3) could the boost-tap be causing extra impedence on the primary?

thanks for any help you can provide!

brother jb

Is this a "normal" 120Vac dimmer?
"Normal" dimmers Don't like inductive loads(such as a transformer),so it
would be no surprise if the dimmers were failing -they're not made for
that usage.

If these are "special" dimmers,made for inductive loads.. I've no idea.
350W could be as high as 700Va,depending on PF,etc,etc.
Perhaps your dimmers are a tad under-rated for the job.