Need some variac advice - Page 1
Forum section: electronics / testgear

author: jpenn
author_rank: Contributor
timestamp: August 13, 2014, 06:23:05 am
content: Hello allI was looking for a variac for my workbench and I came across this 10Amp Powerstat 116BT-2 and I got it for a great price. I'm in the USA and require 120V for my workbench. This variac is two 120V 10A transformers wired for 240V 10A. Some of the ideas I was playing with are,1. My workbench not far from my breaker panel and I can run a in a 240V line. should I run 240V to the variac and split the 240V out of the variac into two 120V outlets?2. Should I run a 20Amp 120 line to the variac and have dual 120V in and dual synchronized 120V outlets?3.Should I leave it as a 240V and just just run it to half scale for running 120V devices?Nah, I didn't like that idea either.4 Is there a way to run the two variacs in parallel for 120V 20A?If anyone can give me some ideas I would appreciate it.I'm leaving the isolation transformer out of the equation for now. I'll have to wait till I see how I am wiring this thing up first.ThanksJohn

author: johansen
author_rank: Super Contributor
timestamp: August 13, 2014, 07:18:50 am
content: You can run them in parallel but i would be very careful with aligning the brushes while watching the circulation current.how did they wire the two up for series operation?

author: gaijin
author_rank: Contributor
timestamp: August 13, 2014, 07:39:14 am
content: Or use a paralleling choke to balance out the voltage difference between variacs.I have a pair of Superior Electric 1156Ds wired in parallel using a T5587 choke.

author: jpenn
author_rank: Contributor
timestamp: August 13, 2014, 02:58:41 pm
content: To johansenSee the wiring diagram below. My powerstat uses the outer inputs and outputs for 240V operation. Wires Red, Black, and Ground. There is no common.To gaijinI did see this in the specs for the larger units 20A and above but there doesn't seen to be any mention of the T5587 choke for the 10A model. Frankly I can't find much info on the T5587 choke at all. I found this on the Jenkins websiteQuoteI'll be damned if I can find page 32!If anyone can give my info on this choke and maybe theory of operation as it relates to phase matching two variacs it would be greatly appreciated.Thanks for the replies,John

author: gaijin
author_rank: Contributor
timestamp: August 13, 2014, 10:57:50 pm
content: yeah the T5587 is meant to be bolted to the side of a 1156/1256.It has two coils each with 12 turns around the core, I'll add some pics with phase dots.

author: jpenn
author_rank: Contributor
timestamp: August 13, 2014, 11:33:12 pm
content: gaijinThat info will help. At least I can see what it looks like. I think I see why there is no real description or pictures to be found on the internet. It looks pretty simple. Now if I can find a theory of operation I will be satisfied. For now I think I've got enough to run with. Those pictures were really helpful. Thanks so much!John

author: David Hess
author_rank: Super Contributor
timestamp: August 15, 2014, 09:25:52 pm
content: I am interested in seeing the theory behind that as well but it does not look like it would be difficult to calculate appropriate values of inductance and saturation current.