Hargraves offers the widest range of motor technologies to achieve the optimal performance of their diaphragm pumps for specific applications. The classifications of DC motors commonly used to power miniature diaphragm pumps include Brush, Coreless, and Brushless.

Fundamentals of DC Motors

A DC motor is an electromechanical device that converts direct current (DC) into rotational mechanical energy. A basic understanding of motor design parameters is useful in understanding the overall pump assembly. The selection of the motor requires knowledge of the diaphragm pump performance requirements and constraints imposed by the intended application. Considerations include torque, RPMs, energy efficiency, life expectancy, reliability, noise, size, weight, and cost when selecting the best motor for the specific application.

In selecting a proper motor design, the pump designer considers the necessary speed and torque (torque constant x current) of the motor at the customer’s specified operating voltage to meet the specified performance conditions (flow at given pressure or vacuum). A factor of safety is applied with Hargraves designs to allow the customer to dead head a pump indefinitely and not damage the motor.

Speed Control

The speed of the electric DC motor will increase or decrease with varying voltage. One method is to use an analog control technique that can be accomplished using a variable voltage power supply or a power rheostat (variable resistor). This method is effective but relatively costly to implement and dissipates considerable energy in the power supply or rheostat.

A more efficient and less costly method to manage motor speed is to use digital controls through Pulse Width Modulation (PWM). PWM changes the effective voltage applied to a motor by interrupting the supply for brief periods of time.

Next: Brush Motors