hi,
i recently got some diodes used in microwaves, on further searching it seems its a bidirectional diode "2x062h" used as a protection diode in microwaves.., has someone used this before?
bidirectional diodes?
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Chris Bradley
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Re: bidirectional diodes?
What is the actual question you are asking? Could you provide a more useful title?
The literal answer is: I think microwave manufacturers have used these as protection diodes ....
... if you need to ask, then I would suggest you may find spending time studying electronics, before attempting work with high voltage, to be a wise expense of your time.
Not spending that time may otherwise be a false-economy - if you get my drift (viz. otherwise you may not have much time to spend).
The literal answer is: I think microwave manufacturers have used these as protection diodes ....
... if you need to ask, then I would suggest you may find spending time studying electronics, before attempting work with high voltage, to be a wise expense of your time.
Not spending that time may otherwise be a false-economy - if you get my drift (viz. otherwise you may not have much time to spend).
Re: bidirectional diodes?
apologies for the incomplete question.....what i wanted to ask was if anyone knows what the current rating for this is, from the datasheet i could find the voltage to be rated for 6kv and 1.5kv in oppositte directions
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Chris Bradley
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Re: bidirectional diodes?
Deepak, why would you want to know the current rating? It is going to be [as far as I know] a clamping diode that forces a fuse to blow if the voltage from the transformer runs too high, such as if a rectifying diode goes bad but doesn't lead to a blown fuse... (I'm sure I'll be corrected if I have that wrong.)
You need a rectifying diode, if your hope is to use it to drive a high voltage DC. As far as I know, this isn't a rectifying diode.
You need a rectifying diode, if your hope is to use it to drive a high voltage DC. As far as I know, this isn't a rectifying diode.
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Carl Willis
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Re: bidirectional diodes?
Deepak,
This kind of component is effectively two diodes in series, one with a high reverse breakdown voltage rating and the other with a much lower rating. It is placed in parallel with the HV capacitor in the usual level-shifted magnetron power supply (which uses a separate rectifier in series with the capacitor).
Its purpose in that configuration is to allow the capacitor to charge to a high voltage of the correct polarity only (negative at the magnetron cathode), which is blocked by the high-breakdown diode in the back-to-back arrangement. If the capacitor experiences high voltage of the opposite polarity, the weaker diode in the pair fails. I don't know precisely what condition is being protected against, but my guess is that a high reactive current circulating through the transformer-capacitor pursuant to a failed main rectifier or gassed-out maggie could cause one or both of these components to not "go gentle into that good night." The cap could overheat and burst in a shower of oil, presumably identified as a worse outcome than the need to swap a couple of semiconductors. Or the transformer secondary could melt down before the core thermal protector opens, ruining the component with the highest commodity value. Engineering of a cheap Chinese appliance is all about pushing the envelope and trimming the margins of safe failure.
In any case, I suspect the "protection diode" is only designed to carry current in the permanently-failed state, making it not worth much to you.
-Carl
This kind of component is effectively two diodes in series, one with a high reverse breakdown voltage rating and the other with a much lower rating. It is placed in parallel with the HV capacitor in the usual level-shifted magnetron power supply (which uses a separate rectifier in series with the capacitor).
Its purpose in that configuration is to allow the capacitor to charge to a high voltage of the correct polarity only (negative at the magnetron cathode), which is blocked by the high-breakdown diode in the back-to-back arrangement. If the capacitor experiences high voltage of the opposite polarity, the weaker diode in the pair fails. I don't know precisely what condition is being protected against, but my guess is that a high reactive current circulating through the transformer-capacitor pursuant to a failed main rectifier or gassed-out maggie could cause one or both of these components to not "go gentle into that good night." The cap could overheat and burst in a shower of oil, presumably identified as a worse outcome than the need to swap a couple of semiconductors. Or the transformer secondary could melt down before the core thermal protector opens, ruining the component with the highest commodity value. Engineering of a cheap Chinese appliance is all about pushing the envelope and trimming the margins of safe failure.
In any case, I suspect the "protection diode" is only designed to carry current in the permanently-failed state, making it not worth much to you.
-Carl
Re: bidirectional diodes?
Deepak Soman wrote:
> hi,
> i recently got some diodes used in microwaves, on further searching it seems its a bidirectional diode "2x062h" used as a protection diode in microwaves.., has someone used this before?
I used to make a living repairing microwave ovens 'til they got to cheap to repair anymore. with all that power running around in microwave ovens, surges can produce tremendous EMF, that diode is not designed to short out, only momentarily does it conduct heavy up to 300 amps in a few mili sec. so constant 60HZ operation it's only 1amp.
> hi,
> i recently got some diodes used in microwaves, on further searching it seems its a bidirectional diode "2x062h" used as a protection diode in microwaves.., has someone used this before?
I used to make a living repairing microwave ovens 'til they got to cheap to repair anymore. with all that power running around in microwave ovens, surges can produce tremendous EMF, that diode is not designed to short out, only momentarily does it conduct heavy up to 300 amps in a few mili sec. so constant 60HZ operation it's only 1amp.
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Andy Jones
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Re: bidirectional diodes?
The Asymmetric Rectifier or Short Protector, as it is sometimes called, is included in the circuit to prevent damage to the high voltage transformer and highvoltage capacitor, in case of a short circuit occurring on the magnetron or high voltage diode. The short protector will cause the line fuse to blow in the above fault conditions.
The device will not conduct in any direction, therefore has no effect on the circuit under normal operating conditions. The peak inverse breakdown voltage of D1 is 6kV and D2 is 1.5kV.
Under fault conditions when a short circuit occurs the peak inverse voltage of D2 will be exceeded, this will cause the diode to go short circuit. This in turn will cause a very high forward current through D1, causing it to go short circuit also. This will cause a dead short to appear across the high voltage transformer secondary, which will blow the line fuse, removing power to the high voltage transformer.
Refer to: http://diagramas.diagramasde.com/otros/ ... aining.pdf
The device will not conduct in any direction, therefore has no effect on the circuit under normal operating conditions. The peak inverse breakdown voltage of D1 is 6kV and D2 is 1.5kV.
Under fault conditions when a short circuit occurs the peak inverse voltage of D2 will be exceeded, this will cause the diode to go short circuit. This in turn will cause a very high forward current through D1, causing it to go short circuit also. This will cause a dead short to appear across the high voltage transformer secondary, which will blow the line fuse, removing power to the high voltage transformer.
Refer to: http://diagramas.diagramasde.com/otros/ ... aining.pdf
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Rich Feldman
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Re: bidirectional diodes?
Hi Andy. Welcome to fusor.net.
Thanks for that informative post.
I can understand the compulsion to log in, when one has been lurking and spots a technical mistake, and has the knowledge & references to set it straight.
Some fine print in the registration dialog says new users are supposed to post a personal introduction in the obvious sub-forum.
Thanks for that informative post.
I can understand the compulsion to log in, when one has been lurking and spots a technical mistake, and has the knowledge & references to set it straight.
Some fine print in the registration dialog says new users are supposed to post a personal introduction in the obvious sub-forum.
All models are wrong; some models are useful. -- George Box