Variac

ben goh · 3rd March 2007, 04:24 AM

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?

Freddybaby · 3rd March 2007, 07:22 AM

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..

Freddybaby · 3rd March 2007, 07:22 AM

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

http://www.diyaudio.com/forums/showt...90#post1148590

myhrrhleine · 3rd March 2007, 02:18 PM

When I use a Variac, I turn up the voltage slowly, watching the amp meter.
So, no surges.
Would this work for you?

Eva · 4th March 2007, 05:32 AM

The own variac produces the surge when it is plugged, and it may be strong enough to trip the circuit breaker

AudioFreak · 4th March 2007, 06:14 AM

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.

fotios · 4th March 2007, 06:56 AM

Make this one DIY power supply with variac and many auxiliaries to get a full control.

myhrrhleine · 4th March 2007, 05:51 PM

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.

myhrrhleine · 4th March 2007, 05:53 PM

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.

ben goh · 5th March 2007, 02:17 AM

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.

3rd March 2007, 04:24 AM	#1
ben goh diyAudio Member Join Date: Jun 2001 Location: nil	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?

3rd March 2007, 07:22 AM	#2
Freddybaby diyAudio Member Join Date: Mar 2007	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..

3rd March 2007, 07:22 AM	#3
Freddybaby diyAudio Member Join Date: Mar 2007	Woops Sorry, I just realized what your doing.. My bad.. See this post http://www.diyaudio.com/forums/showt...90#post1148590

3rd March 2007, 02:18 PM	#4
myhrrhleine diyAudio Member Join Date: Jan 2006 Location: Avalon Island	When I use a Variac, I turn up the voltage slowly, watching the amp meter. So, no surges. Would this work for you? __________________ Just because you can't hear it doesn't mean no one can.

4th March 2007, 05:32 AM	#5
Eva diyAudio Member Join Date: Oct 2003 Location: Near the sea	The own variac produces the surge when it is plugged, and it may be strong enough to trip the circuit breaker __________________ I use to feel like the small child in The Emperor's New Clothes tale


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4th March 2007, 06:14 AM	#6
AudioFreak Warp Engineer On Holiday Join Date: Oct 2001 Location: Queensland, Australia	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. __________________ - Dan

5th March 2007, 02:17 AM	#10
ben goh diyAudio Member Join Date: Jun 2001 Location: nil	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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