mo-ta モーター

October 4, 2006

Should I use a zero-crossing type solid state relay (SSR), or a random phase type to operate the motor?

Filed under: AC Gearmotors, Speed Control Motors — mota @ 3:44 am

Zero-crossing type SSR’s cost more and lasts longer, but is safer in that it reduces sparks since it waits for the AC voltage to become zero before turning on. However, since current is delayed (due to coil inductance), there is still a small chance of sparking. Drawbacks: Delay in starting (waiting for zero crossing) and delay in stopping (due to residual current). ES controllers have a zero-crossing SSR built into them.

When designing a circuit with SSR’s, which reverses a reversible motor on-the-fly, make sure that there is at least a 30ms delay between the CW turning off and CCW turning on. This is because the residual current makes the motor continue CW, while the CCW command will make the motor try to start in the CCW direction. Without a 30ms delay, this could cause a problem in operation. The ES Series already has this 30ms delay built in.

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