This information is accurate as of 7/29/11.
Going back to the first release of Sensor/Unison ELV modules, there has been a lot of discussion about their function with a rack in test mode. After some investigation, here are the facts as we currently know them:
The ELV module circuit must be powered (with the breaker on) before getting a control signal in order for the module to output.
The processor in the ELV module needs to see a zero on the pwm line before it is ready to output. With CEM+/3, test mode supplies a constant +5V signal starting before the module boots so the ELV never starts outputting.
In a Sensor+/3 rack in test mode, it is possible for a working ELV module to have signal LEDs illuminated with no fault indication and still not output.
Caution: Do not remove the CEM+/3 from the rack. To maintain arc flash protection, keep the module within the rack -- only unseat/reseat it from/into the backplane.
DRd uses zero cross blanking time even in test mode. Consequently, an ELV should turn on even after a breaker trip/reset. However, there is a software bug that may inhibit test mode function in some versions of DRd code.
In Brief: The ELV will fire with CEM+/CEM3 test mode IF these steps are followed:
Basically, if you provide power to the ELV10 before the CEM+/3, the ELV10 will not fire.