Importance

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Abstract

An AC electronic variable speed drive unit is used to power an AC induction motor that drives a centrifugal pump at controlled speeds for controlling the flow of a fluid process. The feedback loop controller function is implemented in the variable speed drive electronics, another network device, or may be located in a separate controller. This drive/motor/pump unit is used instead of a more conventional process control valve, with its attending actuator and positioning device, in order to improve the responsiveness, stability, and accuracy of the control loop. Coincidently, it also reduces the energy required for the process by the elimination of pressure drop across the control valve and allows a lower cost, smaller electric motor and pump to be used. Elimination of the control valve eliminates a source of fugitive emission through the valve packing, and reduces maintenance requirements that are necessary for a control valve. An AC electronic variable speed drive unit is used to power an AC induction motor that drives a fan at controlled speeds for controlling the airflow to a boiler or HVAC (heating, ventilating, and air conditioning) system. The feedback loop airflow controller function is implemented in the variable speed drive electronics, another device on the network, or may be located in a separate controller. This drive/motor/fan unit is used instead of a more conventional damper with its attending actuator and a positioning device in order to improve the responsiveness, stability, and accuracy of the control loop. Coincidently, it also reduces the energy required for the air handling system by the elimination of pressure drop across the damper, and allows a smaller fan and electric motor to be used. Elimination of the variable positioning air damper eliminates a source of noise, valuable in HVAC applications, and eliminates maintenance requirements for this mechanical device.

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