Running different rated mains equipment from a variac - Freq. difference?? - Page 1
Forum section: electronics / beginners

author: tec5c
author_rank: Frequent Contributor
timestamp: December 13, 2012, 05:55:00 am
content: I'm considering making the purchase of a Weller WR3000M rework station and have been searching around for different prices etc.It's an expensive bit of gear and I'm finding that the best prices are coming from the USA (including shipping) but they're mains input is obviously 120VAC and as I am in Australia I have 240VAC available.I do have a variac so I can drop the voltage down to 120V but I'm just not sure about the difference in mains frequency (50Hz here, 60Hz for USA/rework station). Are there any problems associated with having a regularly used bit of equipment running from a stepped-down mains voltage at a little lower frequency?I just want to be certain before I commit to the buy.Thanks.

author: tec5c
author_rank: Frequent Contributor
timestamp: December 13, 2012, 07:18:07 am
content: I've been reading around a bit more, and have found that people are saying things like "Using a 110V soldering iron with 240v and step-down transformer will be fine. As the iron is a resistive load and therefore not affected by mains frequency." I understand that, no problems there.But with a soldering iron that is of the level that the WR3000 is, I tend to think it's a little more than just a "resistive load". Am I right here? Or will it still be fine?Thanks

author: AlfBaz
author_rank: Super Contributor
timestamp: December 13, 2012, 07:36:01 am
content: If its got a transformer in it, it'll draw more current than its rated. If you drp frequency you drop its inductive reactance, so it may heat up more. Seeing you are using a variac you could drop the voltage a little more to keep the current at its rating. Aside from that it will probably fine. A schematic of the internals would help if you wanted to be sure. If that's not available, ring weller they may be able to advise you

author: Psi
author_rank: Super Contributor
timestamp: December 13, 2012, 07:43:27 am
content: I'd be very surprised if you encountered any probs.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 13, 2012, 08:40:49 am
content: Over the years a lot of 60Hz stuff has been used on 50Hz with no dramas,but of course,in earlier times transformers were commonly very generously rated to ensure long life & reliability.This may no longer be the case!I am a little concerned about the permanent use of a variac in this service,as one accidental bump to that big control knob,& you will let the smoke out of the transformer.

author: T4P
author_rank: Super Contributor
timestamp: December 13, 2012, 10:30:12 am
content: Could lead to transformers overheating to the point of catching fire and such, it's not entirely safe at all

author: ciccio
author_rank: Frequent Contributor
timestamp: December 13, 2012, 01:31:02 pm
content: I would not use a variac for the permanent operation of the station: the risk of a misplaced knob is too hight.There are two cases:1) the Weller station is built in Europe and sent to U.S. : it can have a dual-primary transformer, rated at 50 Hz (thus it will have no problems at 60 Hz), and by just moving a couple of jumpers it can be converted to 230 V or 115 V operation, or a bigger transformer with primary taps at 115 and 230 V.Maybe searching the station's service manual will give a clue.2) The Weller station is built in the USA, and it has a (slightly cheaper to manufacture) single primary transformer, and they saved every penny by designing the transformer for 60 Hz only (maybe 50 grams of iron saved...). In this case the transformer will be hotter at 50 Hz, but the mean power delivered during operation will be less than 100% (due to heat cycling to the soldering iron), and this will not be of any harm.I looked inside one of my Weller stations: it has a transformer with dual windings , but I don't know if this is the rule.In the years I bought a lot of test instruments from the USA, when they were too expensive here in Italy, and most of the times I disassembled the power transformer and had it rewound for 230 V, with a slightly smaller wire and maintaining the original iron, winding former and secondary winding intact (Making a new transformer will have resulted in some difficulties in mechanical compatibility)They are still operating after some decades and, yes, the transformers are a little warm, but cooler than most modern equipment.

author: tec5c
author_rank: Frequent Contributor
timestamp: December 17, 2012, 06:03:35 am
content: Thanks for all the replies and I apologize for not responding sooner.As mentioned from other members, I think that using a variac is too risky and it would only take a single silly mistake to blow up a few thousand dollars.I did a little more searching and I have found a supplier with a reasonable price who are located within driving distance from me so I have just placed an order for the WR3000M-AU (Australian version-230V input)My bank account took a severe beating this year!!I had no luck finding a service manual though perhaps a warranty voiding (yeah right!) teardown is in order to see what the input circuitry looks like in this beast

author: bson
author_rank: Unknown
timestamp: November 13, 2015, 02:09:14 am
content: Yep. Raising the dead here.So after 3 years, what do you think of the WR3000M? I'm looking at one at my end here to reduce bench clutter, and really like the idea of the vacuum picker. Did you keep the station? Use it still? Problems? Failures? Does the sucker indeed suck?