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Old 3rd March 2007, 04:24 AM   #1
ben goh is offline ben goh  Singapore
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Default Variac

Hi

Can anybody advise me on this.

I want to put a thermistor on the ac line connecting a 2 KVA

variac to suppress the surge, will it work?
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Old 3rd March 2007, 07:22 AM   #2
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Default Whats your application ?

You want to use a variac and thermistor ? Are you sure you don't mean a Varistor ? These are often used for surge limiting.

They are also referred to as MOV or Metal Oxide Varistor.

They go across the AC line and are rated for the working voltage (120-240 vac) and have a clamp voltage above this working voltage.

http://www.littelfuse.com/varistor.html

What are you trying to do ? Maybe I can point you in the right direction..
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Old 3rd March 2007, 07:22 AM   #3
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Default Woops

Sorry, I just realized what your doing.. My bad.. See this post

http://www.diyaudio.com/forums/showt...90#post1148590
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Old 3rd March 2007, 02:18 PM   #4
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When I use a Variac, I turn up the voltage slowly, watching the amp meter.
So, no surges.
Would this work for you?
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Old 4th March 2007, 05:32 AM   #5
Eva is offline Eva  Spain
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The own variac produces the surge when it is plugged, and it may be strong enough to trip the circuit breaker
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Old 4th March 2007, 06:14 AM   #6
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And I wouldn't want the amp connected to the speakers while bringing up the voltage on a Variac.... Some amps don't operate very well until they get a minimum operating voltage and could potentially damage your speakers.
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Old 4th March 2007, 06:56 AM   #7
fotios is offline fotios  Greece
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Make this one DIY power supply with variac and many auxiliaries to get a full control.
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File Type: jpg variac.jpg (99.7 KB, 356 views)
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Old 4th March 2007, 05:51 PM   #8
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Quote:
Originally posted by Eva
The own variac produces the surge when it is plugged, and it may be strong enough to trip the circuit breaker
I never noticed that on any of the variacs I used.
When the secondary is set for zero volts,
How much surge current have you noticed?
It must be a huge surge to trip a breaker.
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Old 4th March 2007, 05:53 PM   #9
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Quote:
Originally posted by AudioFreak
And I wouldn't want the amp connected to the speakers while bringing up the voltage on a Variac.... Some amps don't operate very well until they get a minimum operating voltage and could potentially damage your speakers.

I agree.
Hopefully one would use load resistors.
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Old 5th March 2007, 02:17 AM   #10
ben goh is offline ben goh  Singapore
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Hi

Thanks for the reply and advises

The problem is that without connecting the secondary to any load.

The breaker will trip occasionally when I turn it on. I do not want

to wear out the breaker. It is a 2 KVA china made variac.
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