A Case Study for Infusion Systems: Coreless Brush DC Motor Controls Nutrient Flow for Medical Feeding Pumps

Enteral feeding pumps are medical devices with a built-in tube used to deliver nutrients directly to the stomach of patients who are unable to safely consume food by mouth. The motor systems in these small, lightweight devices must also deliver sufficient torque to ensure continuous flow. The pumps also must be able to adjust flow rates — depending on the nutrition formula and patient needs — with accuracy and precision.

Commutated Resistance Change of Portescap Brush DC Motors

For a one brush pair Portescap DC motor, the catalog value for resistance is specified assuming that all coils are active (that is, no coil is short circuited by the brush, which would occur if the brush were simultaneously touching two commutator segments).

Controlling Brushed DC Motors with Pulsed-width Modulation (PWM)

The enduring popularity of coreless brushed DC motors comes from a combination of their simplicity of design, fast transient responses, negligible iron losses and ease of control. With speed proportional to applied voltage, the motor can be simply driven using a continuous linear regulation power supply. But is this always the best solution?