is transformer with primary and secondary = isolation?

milen007 · 1st February 2011, 05:26 AM

hi guys

i am confuse about the term isolation transformer.

is transformer with primary winding and secondary winding is regarded as isolation transformer?

say normal audio transformer of 0v-15v on its secondary. is this consider as isolation transformer as well which is only output 15v instead of normal 110v or 220v?

or isolation transfomer is something else that not just primary and secondary winding

thanks
erwin

bob91343 · 1st February 2011, 05:30 AM

The usual meaning of an isolation transformer is a 1:1 ratio to supply the same voltage as the primary such that there is no galvanic connection between the source and load.

And yes, all transformers isolate but aren't called isolation transformers.

milen007 · 1st February 2011, 05:36 AM

thanks bob for the confirmation. i am clear now.

erwin

AndrewT · 1st February 2011, 09:58 AM

Hi,
for mains use, isolation transformers are tested to very high isolation voltages. I think 1500Vac for a few seconds.
I doubt an ordinary audio transformer would meet this safety standard. They normally only handle a few volts or at most a few tens of volts.

The output transformer of a valve/tube amplifier may be safety tested to a similar standard as a mains isolation transformer.

Mooly · 1st February 2011, 11:11 AM

Just to add that "auto transformers" and Variacs provide no isolation between input and output yet come in the category "transformers".

Richard Ellis · 1st February 2011, 11:30 AM

A further clarification....True isolation transformers have whats called a split bobbin. The bobbin is the plastic core onto which the primaries and secondaries are wound onto. The "standard" bobbin has both primaries AND secondaries wound on top of each other in an interleaving pattern. The isolating value being the 'tape' that separates each stack of windings. The split bobbin has a large ( 3 mm?) wall of plastic, a barrier that separates both windings. The split bobbin is less efficient but has superior isolating properties.

__________________________________________________ __Rick..........

1st February 2011, 05:26 AM	#1
milen007 diyAudio Member Join Date: Dec 2007	is transformer with primary and secondary = isolation? hi guys i am confuse about the term isolation transformer. is transformer with primary winding and secondary winding is regarded as isolation transformer? say normal audio transformer of 0v-15v on its secondary. is this consider as isolation transformer as well which is only output 15v instead of normal 110v or 220v? or isolation transfomer is something else that not just primary and secondary winding thanks erwin

1st February 2011, 11:11 AM	#5
Mooly diyAudio Moderator Join Date: Sep 2007	Just to add that "auto transformers" and Variacs provide no isolation between input and output yet come in the category "transformers". __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Using primary as the secondary winding in the power transformer.	mishak	Parts	10	30th May 2010 05:55 AM
safest way to identify primary/secondary?	gary h	Power Supplies	15	6th January 2010 03:56 PM
cap btween primary and secondary windings?	sam9	Power Supplies	8	19th May 2005 06:34 PM
Why a Zobel network across OPT primary or secondary?	ray_moth	Tubes / Valves	6	4th March 2005 10:26 PM
Using the secondary of a normal transformer as the primary to get a HT supply	baggystevo82	Parts	9	2nd April 2004 11:02 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

1st February 2011, 05:30 AM	#2
bob91343 diyAudio Member Join Date: Mar 2010	The usual meaning of an isolation transformer is a 1:1 ratio to supply the same voltage as the primary such that there is no galvanic connection between the source and load. And yes, all transformers isolate but aren't called isolation transformers.

1st February 2011, 05:36 AM	#3
milen007 diyAudio Member Join Date: Dec 2007	thanks bob for the confirmation. i am clear now. erwin

1st February 2011, 09:58 AM	#4
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, for mains use, isolation transformers are tested to very high isolation voltages. I think 1500Vac for a few seconds. I doubt an ordinary audio transformer would meet this safety standard. They normally only handle a few volts or at most a few tens of volts. The output transformer of a valve/tube amplifier may be safety tested to a similar standard as a mains isolation transformer.

1st February 2011, 11:30 AM	#6
Richard Ellis diyAudio Member Join Date: Sep 2006 Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence.	A further clarification....True isolation transformers have whats called a split bobbin. The bobbin is the plastic core onto which the primaries and secondaries are wound onto. The "standard" bobbin has both primaries AND secondaries wound on top of each other in an interleaving pattern. The isolating value being the 'tape' that separates each stack of windings. The split bobbin has a large ( 3 mm?) wall of plastic, a barrier that separates both windings. The split bobbin is less efficient but has superior isolating properties. __________________________________________________ __Rick..........