I have an older Ikea quad spotlight system in my workshop for lighting over the wood turning lathe. It uses a toroidal transfomer. I was checking out a portable infra red heater which has a 700w/350w switch
- when switched to the lower setting, the transformer in the light hummed noticeably. Any ideas why ?
Rob
My guess is:
a) You have significant voltage drop in your workshop with the heater on (do the lights dim when the heater comes on?), and b) the heater has only one element, and for the low power setting, it is using either phase control or half-wave rectifier to generate the low power setting.
These two mean the mains sine wave fed to the toroidal transfomer is distorted, and mains toroidal transformers can get a bit unhappy when that happens and start drawing a strange current waveform. In theory, this can cause the transformer to overheat, but I doubt the effect in your case would be bad enough for that.
NT
Thanks Andrew - there is certainly a longish run to the workshop but a
700W heater - it's one of those ones with a bulb like thing and a hyperbolic reflector - is hardly going to load anything significantly, and this is at the half power setting.I didn't realise that toroidal transformers were that sensitive. I did guess it was a non-sinusoidal supply problem but I was surprised that a 30A+ supply would be affected by a 'dirty' 1.5A load, and further the lights and power are on separate mcbs on the local split distribution CU
The 2kw fan heater makes no difference to the lights - the 3kw circular saw does on start up.
Rob
Well, this might not be the correct explanation, but it was all I could think of. It would be interesting to know how the 350W switch works. It's probably really a 'dirty' 3A load. If the 2kw fan heater doesn't cause any dimming of the lights when you switch it on, I'm rather stumped.
In message , Andrew Gabriel writes
snip
A friend with an American camper van (mobile home:-) complained of something similar.
In his case the toroidal step up transformer seemed to be affected by the current load when the microwave cooker was in use. The most noticeable effect was serious smoke from the diesel generator.
regards
>
unlikely
it won't be to any significant extent. Look at the load side of the transformer.
NT
NT - can you explain what you mean by that - it's 100W transformer feeding 4 off 20W GU something-or-other bulbs. Is it possible it's the bulb filaments 'singing' ? Rob
The current waveform drawn by a microwave I looked at had the strangest shape I've seen from any device. Probably not a very high power factor, but I didn't measure it.
Microwave ovens often only half-wave rectify the EHT for the magnatron. They use an oversized EI lamination mains transformer which will cope with this without saturating on the DC component, but a tordoidal transformer won't handle significant DC loads because of absolutely no air gaps in the core. He probably managed to saturate the core, which will cause excess current and overheating of the primary winding, and maybe overloading whatever was suppling it.
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