Last Week's Question
Which of the following transient protection components is a "crowbar" device (so called, because it acts like a short circuit when the voltage across its terminals exceeds the threshold).
- metal oxide varistor
The correct answer is "c". Diodes and metal oxide varistors (MOVs) hold the voltage across their terminals to a maximum constant voltage. Thyristors on the other hand, "turn on" when the maximum voltage is exceeded and effectively look like a short circuit. This is like dropping a crowbar across the bare wires of the circuit causing a short. Gas discharge tubes are also crowbar devices. Fuses are current-limiting devices.