isolation tranformer questions

[matt thomas]

Hi guys

I hope everyone had a great Xmas.

I have a couple of q's

1> How much power does an isolation transformer itself use? I'm guessing not much..

2> Does this vary with the size of the transformer?

3> Are there any safety issues with using one that I should be aware of?

I did do first year electronic engineering at university but have forgotten it all, so answers in layman's terms wold be appreciated

thanks
matt

[S2udio]

Take it were talking mains isolation ? If so
1
No.... As you said not alot,unloaded only iron losses,a few mA ( depending on KVA rating)[size] of iron....1ph/3phase

2
Yes the bigger the KVA the bigger the losses ,More so when fully loaded
Ind/Cap(cos phi).single phase,3 phase losses

3
No as long as mechanically protected (metal enclosure)earthed with secondary centre tap grounded to mains [earth] / the metal box....
Hopefully ....tied to neutral leg of mains at the distribution board.
PME here in the UK.

[matt thomas]

thank s2udio

also, i read that for studio use an isolating transformer should be in a faraday cage. Does the metal box act as one or are they talking something specific which is not included in all isolation transformers?

Btw. I note the one I have has a thermal overload protector, hence I was wondering about the power usage (and also reading in Rod Gervais's book that you need to take this into account when calculating total power usage)

Also, do they always hum?

thanks
matt

[S2udio]

Originally Posted by matt thomas

also, i read that for studio use an isolating transformer should be in a faraday cage. Does the metal box act as one or are they talking something specific which is not included in all isolation transformers

Thats the metal box...a Faraday cage connected to [ground]

Originally Posted by matt thomas

Btw. I note the one I have has a thermal overload protector, hence I was wondering about the power usage (and also reading in Rod Gervais's book that you need to take this into account when calculating total power usage)

Thermal OL is incorperated For safety .....you dont want it overheating ! ,
Ventilation and ambient temperature is important if you drawing a few kw.
Take 10/20% over what your total load is and your safe.

Originally Posted by matt thomas

Also, do they always hum?

Depends on how BIG....all 50/60hz transformers hum,depends on loading , inaudible to most people ears ..
But you dont want it sitting next to or under the desk or an outboard rack !
Thats another story !


Happy new year.

[idylldon]

I have a couple of 30A isolation transformers feeding two 20A circuits in my control room. They are LARGE and they do hum, but I installed them in an adjoining building so they're inaudible in the studio/control room. I wouldn't put them in a control room if that's what you're thinking.

Cheers,
--
Don

[matt thomas]

thanks guys

happy new year

matt

[newdigitaluser]

Originally Posted by matt thomas

Hi guys

I hope everyone had a great Xmas.

I have a couple of q's

1> How much power does an isolation transformer itself use? I'm guessing not much..

2> Does this vary with the size of the transformer?

3> Are there any safety issues with using one that I should be aware of?

I did do first year electronic engineering at university but have forgotten it all, so answers in layman's terms wold be appreciated

thanks
matt

some

yes

dont touch the terminals
dont try to push more power through than the rating

[radeng]

Originally Posted by matt thomas

thanks guys

happy new year

matt

Happy new year.

The hum can be mitigated sometimes with isolation mounts for the transformer (usually rubber). Power quality plays a role too. Harmonics can cause some types of audible noise sometimes.

[KdPyke]

Quick question- Is it ok to plug a power conditioner into an isolator?