How to Minimize the Inductance in a Motor

Replace the motor̵7;s magnetic winding core with a ceramic- or plastic-based substitute to form a core that consists mostly of air. The air core will prevent the energy losses that occur as the motor winding is rotated with a magnetic core, reducing the back EMF and the main cause of high inductance levels.

Identify the phase wires of the motor through their plastic insulation, normally colored orange, black or red. Using a desoldering gun to melt the joints, disconnect each of the wires from the motor, noting where each wire was originally connected. Arrange the wires side by side, and braid them together by weaving the outer wires over the inner wires over and over, forming a singular tight bundle that can be soldered back onto the motor. This braid will keep the wires as close together as possible and reduce the mutual inductance that is created between the phase wires.

Consider adding a snubber to the transistor driving the motor by placing a 100 Ohm resistor in series with a 100nF capacitor between the drain and source pins of the transistor. This configuration will cause the rapidly changing voltage spikes that occur in operation of the motor to be dissipated, limiting the buildup of inductance. As the voltages will be dissipated through the resistor as heat, consider attaching a heat sink to the resistor to stop the temperature from rising high enough to cause damage.

Check the types of capacitors used to construct the motor and its driving circuit. This information will be printed on the plastic cover of the capacitor and will be of either aluminum or tantalum. Aluminum capacitors have a much higher inductance compared to their tantalum counterparts, therefore producing higher amounts of inductance, and so you may choose to use the superior tantalum type. However the use of tantalum capacitors will significantly increase the cost of your project, and will explode dangerously if improperly connected.