Hobbyist: Variac & Isolation Transformer in one unit or separate? Opinions wanted: - Page 1
Forum section: electronics / beginners

author: brokenbones
author_rank: Newbie
timestamp: September 21, 2017, 07:19:31 pm
content: Getting ready to buy an isolation transformer and variac for audio and guitar work. <500W. Hobbyist work.Are there any advantages to having a separate transformer and a separate variac?I've seen newer and vintage units that house both pieces and i'm wondering what if there are any advantages/disadvantages to either setup.https://www.artisantg.com/TestMeasurement/72452/Sencore_PR57_Variable_Isolation_Transformer_Safety_Analyzer(newer)http://www.bkprecision.com/products/power-supplies/1655A-150v-3a-ac-power-supply.htmlThanks in advance.

author: cdev
author_rank: Super Contributor
timestamp: September 21, 2017, 07:31:47 pm
content: Just make sure people know without ambiguity, that a Variac is an autotransformer and in itself doesn't isolate from the mains. Its a separate issue it addresses.Those units seem targeted at people who would likely know that, and I suspect they likely combine them for extra safety. Which would be good IF the unit also has an indicator light or alarm or something to tell the serviceperson that although the unit was isolating it, that a plugged in unit had a ground fault issue..

author: Benta
author_rank: Super Contributor
timestamp: September 21, 2017, 08:27:23 pm
content: On principle, I don't like combination instruments or tools or machines etc.It limits flexibility and bars you from combining your toolbox in the best way.As examples: combo lathe/milling machines: both parts work only half as well as separate machines. Combo multimeters/scopes: yes, but the scope display is crap compared to a real scope, and the multimeter part has limitations due to lack of connections/functions, plus you can't measure in two places at the same time. etc. etc.In your example, I'd split the safety transformer and the variac as well. You never know if you'll need the variac at one end of your workbench, and the isolation transformer somewhere else.It all looks very handy and smart, but I really only see a need for combination equipment if your work area is very space limited.Just my 2 cents.

author: Zero999
author_rank: Super Contributor
timestamp: September 21, 2017, 10:22:32 pm
content: Just a note about safety: obviously be careful when dealing with hazardous voltages (AC is more dangerous, then the same DC voltage, as it's more likely to interfere with the rhythm of the heart), but beware that there are failure modes with variacs, even the isolating variety, which can cause the secondary voltage to be much higher than the set value.

author: Electro Detective
author_rank: Super Contributor
timestamp: September 21, 2017, 10:55:08 pm
content: I prefer the option of separates.I can rig the isolation transformer to how 'isolated' I need it to be, be it ground/earthed or not, and/or neutral/earth ground link variationsand be able to use the isolation transformer first, variac second in the chain, and vice versaPut lamps, multimeters, clamps, scopes wherever required in the chain to indicate voltage in/out, current, faults etcSeparates are easier to check and service etcThe All In One is a nice no brainer (and looks cool), but not for some total voltage control types like me

author: lordvader88
author_rank: Frequent Contributor
timestamp: September 21, 2017, 11:02:39 pm
content: For my hobby on a little bedroom desk, I want a box on the floor I can just plug into with minimal extra wires to worry about.So I'm putting going to make it all in 1.

author: Brumby
author_rank: Unknown
timestamp: September 22, 2017, 01:38:14 am
content: I'm also a fan of separate pieces.Separate pieces tend to be better at their specific purpose, where combined units often compromise. The flexibility of configuration is another aspect as well as the fact that if one part of a combined unit is out of commission, then the working part is unavailable while the whole thing is away for repair.Certainly, when space is an issue these things can take a back seat, so long as the chosen unit is adequate for the job.And I apologise if I am sounding like a broken record, but be aware of the risks and limitations of this gear. These things are designed to handle some power at mains voltages. You can get yourself into serious trouble very quickly if you are not careful. Stay safe.