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cava0035
What is the difference between a Zener Diode and a Transient Voltage Suppressor Diode? Aren't they the same? Can you give an example of each?

Thanks,

Guest_Bob
QUOTE (cava0035+Jul 5 2006, 07:14 PM)
What is the difference between a Zener Diode and a Transient Voltage Suppressor Diode?  Aren't they the same?  Can you give an example of each?

Thanks,

A Transient Voltage Suppressor (Transorb) is a zener diode that is engineered for high power operation. Some transorbs are "bidirectional". In other words, they consist of two zeners in one package.

If you want a precision zener with good low-current operation, you would buy a 1N4739 or something similar. If you want a device to clamp the inductive kick of a relay coil, you would buy a 1N6272 or something similar. The 1N6272 is specified to work and survive 93 amp peak current pulses but the 1N4739 is only specified at 28mA.

Bob
george mountcastle
QUOTE (Guest_Bob+Aug 24 2006, 05:14 PM)
A Transient Voltage Suppressor (Transorb) is a zener diode that is engineered for high power operation. Some transorbs are "bidirectional". In other words, they consist of two zeners in one package.

If you want a precision zener with good low-current operation, you would buy a 1N4739 or something similar. If you want a device to clamp the inductive kick of a relay coil, you would buy a 1N6272 or something similar. The 1N6272 is specified to work and survive 93 amp peak current pulses but the 1N4739 is only specified at 28mA.

Bob

I hope I am in the right area. My needs are to clamp inductive voltage surge from coils and inductive loads 12vdc mobile operation that have current loads of .5 to 50 amps. What is the right trans-orb to use?
StevenA
QUOTE (george mountcastle+Sep 29 2006, 06:18 PM)
I hope I am in the right area. My needs are to clamp inductive voltage surge from coils and inductive loads 12vdc mobile operation that have current loads of .5 to 50 amps. What is the right trans-orb to use?


Here are a few things to consider for this:

You want to limit the peak voltage spikes, but of course not drain much current around 12V. A typical lead acid battery, will have a voltage higher than 12V. I'd guess the battery voltage should remain below 16V though, so you would want a device that doesn't draw much current at 16V.

The maximum voltage from a spike needs to be determined. I don't know if there's an industry standard maximum withstanding voltage designed into most 12V battery systems, but I'd assume most should be able to handle short spikes at maybe 24V. Allowing a higher voltage would make the design easier but adds more risk to devices powered on it.

The amount of inductance in the system will determine how much power handling is necessary by the device(s). The more inductance, the more energy will be needed to be dissipated.

Also, if the spikes are repetitive (from switching circuits) then you'll have a constant power being put into the absorbtion and heat sinking the devices would be very beneficial in this case as the limit would not be for single spikes but be instead limited by the overall rate of heat they're able to dissipate.

Here's a link to a Digikey page you can search using filters to isolate what devices might be suitable. Basically, you want a device that draws little at 16V and pulls the maximum current before ~24V and is large enough to absorb whatever inductive sources generate the spikes.

http://www.digikey.com/scripts/DkSearch/dk...US&Cat=31917227
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