Solid State Motor Starter Relay 

(SMR-220)

Typically, some motors and compressors need high starting torque. To generate a high starting torque a high starting current is needed, which can be generated by connecting a start capacitor in series with the motor’s start winding.The start capacitor must be disconnected as soon as the motor speed reaches 75% of its full load speed. Keeping the start capacitor connected will produce a high current that would destroy the start winding. For this reason, it’s important to have to reliable device to disconnect the start capacitor accurately.

SMR-220 solid state relay is a patent pending electronic replacement for potential starting relays which are used with single-phase capacitor start motors. SMR-220 electronically senses voltage across the start winding. When the voltage passes a certain level the relay disconnect the start capacitor from the start winding. Compared to mechanical potential relays, SMR-220 is more durable and reliable. Since it can tolerate more voltage and current spikes, it has a longer lifetime.

Solid State Relay Vs Electromechanical Relay

Solid State Relay

  • Generates minimal electrical disturbance

  • Low power consumption

  • Highly resistant to shock and vibration

  • Responds to control systems in less than 100µs

  • Does not generate sparks or electric arcs

  • Positional insensitive, suitable for mounting horizontally and vertically

Electromechanical Relay

  • Generates a significant noise as a result of mechanical system

  • Requires higher input power to operate

  • Subject to external forces that can lead to unreliable and erratic operation

  • Can respond to control signals in 15ms (100 slower)

  • Generates arcs, so it isn’t suitable for some environments

  • External forces must be perpendicular to relay action