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SCR phase speed control for tools or appliances

2015-02-28 06:05  
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New technologies such as variable-speed motor control allow appliances to be more energy-efficient, and home networking enables home owners to control and monitor the energy usage of all household appliances that are connected to the same network. Most standard household appliances and portable hand tools can be adapted to variable -speed operation by use of this simple half-wave SCR phase control. It can be used as the speed control unit for the following typical loads pro-videe they use series universal (brush type) motors. During the positive half cycle of the supply voltage, the arm on potentiometer R2 taps off a traction of the sine wave supply voltage and compares it with the counter emf of the motor through the gate of the SCR. When the pot voltage rises above the armature voltage, current flows through  CRI  into the gate of the SCR, triggering it, and thus applying the remainder of that half cycle supply voltage to the motor. The speed at which the motor operates can be selected by R2. Stable operation is possible over approximately a 3-to-l speed range.variable speed motor drives gives an opportunity to have more sophisticated control programs.Variable speed motor drives gives an opportunity to have more sophisticated control programs. This enhances the appliance performance and increases overall energy efficiency. Thus home appliances equipped with variable speed drives and intelligent controls consequently out-perform electronically uncontrolled motor drives and improve home appliance performance over motor drives with fixed speeds.

Plug-in speed control for tools or appliances