Anyone who have any experience about using relays designed for 230Vac use in high voltage circuits.
How large voltages can these relays can tolerate, are there any risks about using relays in high voltage circuits?
I would like to hear any experience about using relays in high voltage circuits.
How large voltages can these relays can tolerate, are there any risks about using relays in high voltage circuits?
I would like to hear any experience about using relays in high voltage circuits.
My answer is no but you have a spark at 3 kV per mm (when the air is dry!). You could increase the reliability by connecting the contacts in series if you have 2 poles or more. Real HV relays are big and expensive.
May I ask your application? Maybe it's better to switch somewhere else where the voltage is lower?
This is dangerous stuff
I hope I will not turn up in the Sin Bin for this? 
May I ask your application? Maybe it's better to switch somewhere else where the voltage is lower?
This is dangerous stuff
I hope I will not turn up in the Sin Bin for this? 
Gunderz said:
I'm with Peranders on this.
Switching AC is one thing; DC quite another - and quite often I am frustrated by having to face up to the fact that there is no simple way to switch high voltages.
In one of my amplifiers, I am using two pairs of taps to derive a +ve HT and a -ve HT; I have used a 6v AC-actuated relay that is rated at 250v (AC) so I am getting away with it, becasue I am switching AC.
The only cheap possibilty is perhaps a vacuum switch - as used with mercury rectifiers; I have some - DLS 10s - but you would have to investigate the data to see if DC is "on the menu"
7N7
So.. it's no good idea for me to use a relay designed for 230V in my power supply where the voltage is about 470V?
Which other methods do I have to obtain a switch??
Could I use MOS-FET??
One problem with MOS-FET is their relative high ON-resistance compared to the resistance through a relay. And maybe they need some protection too.
Which other methods do I have to obtain a switch??
Could I use MOS-FET??
One problem with MOS-FET is their relative high ON-resistance compared to the resistance through a relay. And maybe they need some protection too.
Yes, one reason why I planning to use relays is because I want to have a delayed start up for the main supply.
One way to solve the problem will be to use separate transformers for the mainsupply and the heater supply, but the transformer I use now have both main and heater windings.
And I do currently have about 10 2-pole relays who I would like to use.
One way to solve the problem will be to use separate transformers for the mainsupply and the heater supply, but the transformer I use now have both main and heater windings.
And I do currently have about 10 2-pole relays who I would like to use.
My first choice would be to bite the bullet and power the filaments separately, switching the B+ transformer at its primary. Second choice would be, assuming you're using a CT secondary with the CT grounded, to insert a HV bipolar or FET in the CT-to-ground lead and switch it on with a time delay. The "on" resistance will be pretty negligable.
For cost-no-object, you can build a slow turn-on HV regulator. But if cost were no object, you'd be using separate filament transformers!
The hard way is to use a tube rectifier, but you'll have objectively poorer regulation, more heat, and lower reliability. But there's a certain coolness factor that I understand.
For cost-no-object, you can build a slow turn-on HV regulator. But if cost were no object, you'd be using separate filament transformers!
The hard way is to use a tube rectifier, but you'll have objectively poorer regulation, more heat, and lower reliability. But there's a certain coolness factor that I understand.
Frank,
I thought my reply was succinct.
Valves make very good relays, as do transistors. Exhibit 1: the computer I'm presently typing on.
But valves come in high voltages.
You could be right about the IQ. After all, I'm at one with the Belgian, French, German position over Iraq. And we all know that the "cleverest" people are American (with the Brits up their **** of course). After all, only stupid people don't want to go to war...
I thought my reply was succinct.
Valves make very good relays, as do transistors. Exhibit 1: the computer I'm presently typing on.
But valves come in high voltages.
You could be right about the IQ. After all, I'm at one with the Belgian, French, German position over Iraq. And we all know that the "cleverest" people are American (with the Brits up their **** of course). After all, only stupid people don't want to go to war...
It will work fine, but add a little trick to keep the spark from pitting your contacts. Add a .01 1KV cap between your contacts [top to bottom I assume] and a .001 1KV cap from bottom contact to ground to keep things from sparking. Maybe not the best setup but will work and with this voltage may not need it at all, better safe than replacing relays someday.
dhaen said:
Yes, I use Protel for drawing schematics and PCB layouts, though I only use the Protel 99SE, I haven't got a crack for the Protel DXP version yet.
I know some of you don't like the PCB thing.
Back to the relays....
The conclusion is that it's ok for me to use a relay the way showed in the schemtic I posted as long as I add some protectioncapacitors?
Are there other thing I should be aware of while using relays in high voltage circuits.
And the thing about using vacuumtubes instead of a relay, I don't quite understand.
Wouldn't there be a quite large voltage drop over the tube, and how much current can I accept through this tube??
jackinnj said:
Yes, I have also seen switches connected to the centertap, but unfortunately my transformer don't have a centertap.
But wouldn't it be a problem to use 'normal' switches in high voltage circuits too??
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