Actions
Forum Thread Details
  • State Suggested Answer
  • Replies 37 replies
  • Answers 2 answers
  • Subscribers 364 subscribers
  • Views 5107 views
  • Users 0 members are here
Related

Are there any adverse effects from isolating the AC power supply on my electronics bench?

4ringfan

happened to show me an Ebay listing the other day and it was like feeding candy to a baby.  My dad, he can be such an enabler!  Hehe!  So, the long and short of it is that I have acquired this BEAST (a Powervar 12 Power conditioner) and I am planning to modify it so that I can isolate and supply power to my entire bench.  The Powervac 12 is capable of supplying 12Amps at 120VAC, so the only thing I was thinking that I needed to be concerned with was possibly exceeding the supply capabilities of the transformer -- however I find the possibility of drawing that much power quite remote. So...


Here are my primary questions:


  1. Is there any reason or side effect that would contradict hooking the entire bench on the isolated secondary side of a transformer?
  2. Are there other things that I should be concerned with safety wise or otherwise plan for?
  3. Modification suggestions?
  4. In general, is this a good or bad idea?


I haven't found too many articles that talk about this, but here are links to a few that I have looked at:


isolation transformer - Electronics Forums


RadiolaGuy.com : Sonny's Tech Tips


http://www.signaltransformer.com/sites/all/pdf/IsolationTransformers%20Increase%20Safety%20of%20Electronic%20Systems.pdf


isolation - Why are we not always isolating the mains supply? - Electrical Engineering Stack Exchange


I have read the following and I take it that I should not connect any of my test equipment to the isolation, only projects that I am working on. What about power supplies?  What is the take on this?:

 

"DO NOT plug your test equipment into the isolation transformer, just the radio. I've seen folks wire their isolation transformer to a plug strip with all their equipment plugged into it and wonder why their "scope's" ground lead went up in smoke when they connected it to the radio chassis. If all your equipment is plugged into the isolation transformer, then nothing is "isolated"! Only the radio (or television) under test should be plugged into the isolation transformer!"


image

image

image


image



Parents
  • 0

    As for the Isolation transformer itself. The following has been taken from a document called Safety in electrical testing at work: http://www.hse.gov.uk/pubns/indg354.pdf

     

    • Where an isolating transformer is used for the supply to the equipment under test, it should comply with BS 61558 and a separate transformer used at every test bench. If this is not reasonably practicable, the same isolating transformer may be used for supplies to alternate benches, provided the risk of referencing this supply to earth at any bench is properly controlled and the transformer does not then have an unacceptably high leakage current;
    • The supply from the isolating transformer should be provided from a single socket outlet and clearly marked ‘only for use for making live equipment under test’. No fixed wiring should be connected to the earth terminal of the outlet socket. The face plate of the socket should be made of insulating material. There must be no unnecessarily exposed live parts on equipment under test;
    • When the equipment under test is Class I, any pre-existing earth fault must be detected and corrected before making the equipment live. In the case of the supply from an isolating transformer, failure to do this will mean that there may be a hazardous shock risk, if there is a simultaneous contact between the enclosure of the equipment and one or both poles of the isolated test supply;
    • The integrity of the circuit protective conductor (earth) of all portable/ transportable Class I equipment must be re-tested after all test-bench work has been completed, to make sure there are no earth faults before the equipment is used again on a normal mains supply.

     

    It should be clearly understood, however, that an isolating transformer cannot prevent an electric shock if someone makes contact simultaneously with both conductors of the supply on the secondary side of the transformer, unless the output voltage is below 50 V ac (120 V dc) in dry conditions and 16 V ac (35 V dc) in wet conditions.

Reply Children