As I start to set up my work bench, I've been looking at various isolation transformers, and I wondered if they have ones that use a variac as a secondary? I know variacs are autotransformers so it's just one winding, but couldnt that mechanism be implemented as a secondary winding in a regular transformer? In other words it would be a 1:1 transformer with an adjustable variable center-tap? Thanks!

  • \$\begingroup\$ So what great thing does that achieve? An idea without a purpose is just an idea. \$\endgroup\$
    – Andy aka
    Nov 12, 2016 at 0:16
  • \$\begingroup\$ The great thing is the combination of ISOLATION with VARIABLE OUTPUT. Else you must use a separate iso transformer and variac. \$\endgroup\$ Nov 12, 2016 at 0:55
  • \$\begingroup\$ Richard Crowley is correct, I can get isolation and a variable A/C source in one package as opposed to two separate, large, expensive unit. Just do a google search on how much isolation transformers cost and how much variable autotransformers cost and you'll get an answer on what the purpose is. \$\endgroup\$ Nov 12, 2016 at 15:14
  • \$\begingroup\$ The subject title is confusing - the question sounds as if it is asking for a center tap transformer with the ability to adjust the center (e.g. to be 60:40 rather than 50:50). Is that what you are asking for or is it an isolating Variac? \$\endgroup\$ Dec 16, 2016 at 22:12
  • \$\begingroup\$ The title is clearly wrong. If it is "variable" then it isn't necessarily "CENTER-tapped" and vice-versa. \$\endgroup\$ Dec 17, 2016 at 3:33

1 Answer 1


You must be thinking about an isolated variac

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