| 摘要 |
A solid state relay prevents the damage to photothyristor couplers when their performance characteristics vary slightly and enables phase angle control of an AC power supply using a less costly configuration than relays with photothyristor couplers having zero-crossing functions. The solid state relay includes a pair of input terminals configured to receive a control signal, a pair of output terminals configured to be connected to an AC power supply, a thyristor in parallel to the pair of output terminals configured to switch the AC power supply in response to the control signal. The solid state relay further includes two photothyristor couplers, each having a photothyristor, that are connected in series at a midpoint connection. The two photothyristor couplers are connected in parallel to the thyristor and are configured to control the thyristor. The solid state relay further includes two surge arresters connected in series at a midpoint connection that is connected to the photothyristor midpoint connection. The two surge arresters are connected in parallel to the pair of output terminals and are configured to block excessive voltage levels.
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