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Anonymous Poster #1

Diodes Rating

01/28/2012 8:04 AM

I just want to know how are diodes are specified when you are to buy from electrical shops?

Is it rated by Voltage, Amperage, Wattage, Voltage drop? I heard from someone you could buy a diode at 600V, is that true?
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JohnDG
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#1

Re: Diodes Rating

01/28/2012 8:30 AM

Study the datasheet for a typical small-signal diode - e.g. 1N4148.

Yes, there are plenty of 600V diodes available. Click here.

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Winfield Hill
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#2

Re: Diodes Rating

01/28/2012 8:57 AM

They are generally rated for RMS and Peak current, as well as for maximum reverse voltage. Silicon diodes have a nominal 0.6-volt voltage drop when conducting, but this increases with current by 60mV/decade + a resistive voltage drop, and the total forward drop can reach several volts. This is especially true for diodes with reverse-voltage ratings to 1.2kV, they tend to have higher forward voltages. You can get special high-voltage diodes, e.g., which are made from multiple 1kV diodes in series, these will obviously have even higher forward voltage drops.

Diodes with reverse ratings of 600 to 1200 volts are available in many sizes, from very small surface-mount types, to medium-size axial-lead types (e.g., 1n4007 or 1n5408, links), to huge parts with bolt connections or compression pucks. The pictured part is a 1650A rms, 1600V diode made by Infineon / eupec, and costs $194 each at Mouser. It's called a D798N (link), and has a forward voltage of about 1.3 volts at 1.5kA. I think that's about as big as you can get from the mainline distributors.

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Mevel123
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#3

Re: Diodes Rating

01/28/2012 11:22 AM

When you say "buy a diode at 600V" it sounds like you want it to "turn on" at 600V.

You could also be saying you want it to be able to "block" up to 600V.

If I assume it is the first case, then you are looking for a special type of diode known as a 'zeiner' These behave slightly different than a diode. They are intended to conduct in the reverse direction at a specified 'break' point ie 600V. In the forward direction they conduct at the normal .6V-.7V

If it is the second case, and you want to block up to 600VAC, you need to consider that you do not spec the blocking voltage close to the actual supply voltage. If you have a 575VAC line do not use a diode with a Peak Inverse voltage (PIV) of 600V. It will fail due to noise and other variances. Typically when used to rectify (block) AC the PIV of the diode should be at least 2X the nominal supply volts -

Again not sure which case you are asking, but I hope this helps. Also the other 2 answers before mine are very good, and accurate.
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SimpleMind
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#4

Re: Diodes Rating

01/28/2012 1:09 PM

For someone asking this question the only useful (and safe) information is the part number, the price, and a technician's phone. S.M.

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madhavdivya
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#5

Re: Diodes Rating

01/29/2012 9:45 PM

Take Simplemind's advice. As mains power is involved here and you do not have an idea of selecting the RIGHT diode, better keep off for your own safety.
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Previous in Forum: Reading Between Earth and Neutral 120V   Next in Forum: Separating Earth Pit for AC and DC (UPS and Battery Bank)

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