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got a problem with dimmer powered from UPS

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umerhuzaifa

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got a problem

my father is a surgeon and he employs a microscope having a bulb(i guess
incandescent,though i m not confirmed) with a dimmer with it..now as far as the main power is given to the scope the dimmer works fine bt as the main power goes out and it is operated on UPS(uninterrupted power supply),the dimmer works nomore ,the intensity of bulb increases at once n usually burns out..
hope anyone knows how to tackle this problem..
main power and UPS hav folllowing specs..
220V 50CPS
 

keith1200rs

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got a problem

It is probably caused by the output of the UPS being a rather poor sine wave and so interfering with the dimmer, particularly if the sine is distorted around the zero crossing point.

It is difficult to suggest a fix without seeing waveforms/circuits etc, but adding some inductance and capacitance as a filter may help. Make sure you use mains rated components and class X capacitors. A quick thing you could try would be a ferrite clamp on the mains cable.

Keith.
 

IanP

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It sounds like your UPS produces square wave output and unfortunately common phase-angle dimmers won’t work ..

My best advice is to get another UPS that generates at least “modified” sine wave but the best choice would be one with pure sine wave output ..

Rgds,
IanP
 

pranam77

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I had experienced a similar problem where the dimmer was not able to detect perfect zerocrossings in the UPS as it was too distorted. The remedy i had was i changed the circuit from 220 volts to 12 volts and constucted a DC dimmer...It's fine even today since more than 5 years now...
 

Tahmid

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Hi,

I think the problem is that the output from the UPS is square wave or modified square wave, which are most common for a normal UPS. Your dimmer is designed to use sine wave as it uses (most probably) phase angle controller with triac and this method can not be done unless your waveform is sine. If, however, you plug it into a pure sine wave output UPS, your dimmer should work fine.

Hope this helps.
Tahmid.
 

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