Skip to main content

Reply to "Airpax Snapac "Instant" Hydraulic-Magnetic Circuit Breaker"

@SteveH posted:
If/when they do fail, there are two possible failure modes:
  1. The most common, is they can fail in a permanently shorted condition.  It should be obvious when this happens because they will trip the breaker.
  2. The much less common way TVS diodes can fail is that they fail in a open state and will no longer provide voltage surge protection.  This is more difficult to test for and is the reason some people replace them regularly.  Testing for this second failure mode can be accomplished by removing them from the layout and briefly connecting them to an independent voltage source slightly higher than their breakdown voltage (37.1 volts) and measuring current through them.  If they no longer conduct sufficient current above the breakdown voltage, they should be replaced.

There are actually three failure modes.  As Steve says, the predominant failure mode is shorted, this is the most common failure mode.  They can also fail open, and finally degraded.

The typical method of testing a TVS is by using a curve tracer or simply a current limited power supply and a voltmeter or 'scope.  Most times if the TVS isn't shorted, the only way you'll know if it's defective is by removing it from the circuit for testing.  Given the low cost of the TVS device, that's typically counterproductive.  Once you're removed them from the circuit, most people simply replace them if they suspect they're compromised open or degraded.  Testing would be far more expensive than the replacement part.

OGR Publishing, Inc., 1310 Eastside Centre Ct, Suite 6, Mountain Home, AR 72653
800-980-OGRR (6477)
www.ogaugerr.com

×
×
×
×
×