FAQ No. FAQ02075
Question
What should be done about surge-absorbing
circuits for AC-load Solid-state Relays (SSRs)?
Answer
Measures against AC Switching SSR Output Noise
Surges
1. The SSR has a built-in snubber circuit to smooth out a sudden rise in
voltage. If there is a large voltage surge in the output-side AC power
supply, the snubber circuit will not be sufficient to suppress the surge,
and overvoltage will damage the output elements.
2. The following models have a built-in surge-absorbing varistor:
G3NA,
G3S,
G3PA,
G3PB,
G3NE,
G3J,
G3NH,
G9H, G3DZ (some models), G3RZ,
G3FM
3. Be sure to take measures against surge when switching an inductive load
with an SSR that does not have a built-in surge-absorbing element. (Refer
to the following figure.)
Note: A separate varistor with a surge
resistance higher than the built-in varistor must be mounted externally if
influence is possible from noise that is not completely absorbed by the
built-in varistor (surge resistance: 700 to 1000 A).
Select a surge-absorbing element that meets
the conditions in the following table.
|
Voltage |
Varistor voltage |
Surge resistance |
| 100 to 120
VAC |
240 to 270
V |
1,000 A min. |
| 200 to 240
VAC |
440 to 470
V |
| 380 to 480
VAC |
820 to
1,000 V |
Other Solid-state Relay
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