Using a TVS diode instead of, or in addition to a MOV for AC line protection?

For 220 V AC mains voltage, is it good practice to replace a 300 V MOV with a 300 V bidirectional TVS diode (like in here http://www.littelfuse.com/products/tvs-diodes.aspx), or connect both in parallel? Are there any points that need to be considered?

Answer

It comes downto what are you trying to protect against

There are four main types of transient suppression devices

Gas Tube

• Protection time: > 1us


• Protection Voltage: 60 - 100V


• PowerDissipation: Nil


• Reliable Performance: No



• Expected Life: Limited


• Other: Only 50-2500 surges, can short powerlines

MOV

• Protection time: 10 - 20ns


• Protection Voltage: > 300V


• PowerDissipation: Nil


• Reliable Performance: No


• Expected Life: Degrades



• Other: Fusing required. Degrades

Avalanche TVS

• Protection time: 50ps


• Protection Voltage: 3-400V


• PowerDissipation: low


• Reliable Performance: yes


• Expected Life: long


• Other: Low power dissipation. Bidirectional requires dual

Thyristor TVS

• Protection time: <3ns


• Protection Voltage: 30-400V


• PowerDissipation: Nil


• Reliable Performance: yes


• Expected Life: long


• Other: High Capacitance

http://www.onsemi.com/pub_link/Collateral/HBD854-D.PDF

( http://web.archive.org/web/20051001082352/http://www.onsemi.com/pub/Collateral/HBD854-D.PDF )

http://www.vishay.com/docs/88440/failurem.pdf