Brushed motors have driven blower, fan, grinder, and vacuum designs for more than 100 years. They remain more relevant than ever as their core strengths — simplicity in control, cost-effectiveness, reliability, and high peak torque outputs — are continually complemented by innovations that extend useful life and applicability.
Consider universal motors from the Lamb division of AMETEK Dynamic Fluid Solutions (DFS) mass-customized for use in an array of consumer and commercial-grade appliances. As AMETEK DFS application engineering manager Kevin F. Martin explains, these are universal drive motors — brushed motors — with field winding and armature in series.
Such motors deliver high starting torque, which is a characteristic useful to grinding and mixing machines in particular. The magnetic path through the motor includes lamination stacks that minimize eddy currents that arise upon power input. Speeds range from a thousand or so rpm to many times higher … which is also useful in designs that might run to nearly 30,000 rpm at their fastest.
Of course, one mechanical wear point is that at the rotor’s commutator interface with the brushes. But brushes are one of the few motor subcomponents that end users can easily change themselves.
How to Change the Brushes
Shown below is how to change the brushes on a 5.7-in. vacuum motor. First remove power from the motor. Take a flat blade screwdriver and bend back the metal safety clips so they’re no longer over the plastic cap. Then use the screwdriver to pry up on the plastic cap — to pop the cap loose. Once the cap has been removed the brush mechs are exposed. Take the flat blade screwdriver and locate the brush clip. Using the screwdriver press down firmly and push the clip towards the center of the motor. The clip should slide out from under the black nylon of the brush mechanism. Once the clip is free from the brush then remove the two screws holding the brush clamp in place. When the two screws have been removed then lift the clamp up and you can now remove the brush.
Now install the new brush and start the brush clip into the nylon. Next use the top bracket of the motor to press the clip all the way into place. Put the brush clamp in place using the two screws. Repeat this for the second brush, once done, press the black plastic cap back into place until both sides click. Then bend the metal safety clips back so that they help hold the plastic cap in place.
One caveat is that brushed can’t be changed an infinite number of times because the commutator upon which they ride is also a wear item. The general rule of thumb is that brushes can be changed two or three times before the commutator on the rotor reaches the end of its useful life — and renders the motor itself unserviceable.
At AMETEK Dynamic Fluid Solutions, we understand you’re looking for more than just an off-the-shelf part or one-time solution. You need a true technology partner who understands your engineering challenge that is focused on you, providing customized, collaborative solutions. We’ll also provide you with excellent customer service for a great total experience.