Alternistor
From Wikipedia, the free encyclopedia
Alternistor is a trade name for a proprietary class of TRIAC with an improved turn-off (commutation) characteristic made by Teccor and other companies.
These devices are made specifically for improved commutation when controlling a highly-inductive load, such as a motor, an application which causes problems for "normal" triacs due to high voltage/current angles. Most triacs' commutation with inductive loads can be improved by use of a "snubber network", but alternistors are made specifically for this purpose and they dispose of the snubber requirement altogether. This improvement is achieved at the expense of the ability to trigger the device in the 4th quadrant (negative voltage and positive gate current). However, this is usually no problem, because this trigger mode is seldom used since even normal TRIACs are least sensitive there.
The majority of other semiconductor manufacturers, such as ST Microelectronics and Philips have their own versions of improved commutation triac, but they are not marketing them under the proprietary "alternistor" moniker (ST uses the trademark "SNUBBERLESS").
