You are here

Thoughts on DC Motors | Cypress Semiconductor

Thoughts on DC Motors

Originally DC(and universal) motors had brushes to switch (or commutate) the current through the armature windings. Explanations can be found on Google. It relies on having position base switches (commuctator) to determine the correct switching time. The problem is that the brushes wear out and can be noisy.
 
Later brush-less motors came out that used a Hall effect sensor to determine the position of the rotor to allow the field direction to be reversed at the proper time.
 
Lately people have been using the back EMF of the motor to determine the rotor position.
 
I have been thinking about improvements in commutators.   Brushes wear out be cause they are required to switch high current inductive loads. This is called hot commutation and it requires the design of a commutator that suppresses the arcing coming from inductive switching. The brushes need to be very low in resistance and are generally made from carbon and silver. Being soft they quickly wear out.  Why not cold commutation? That is use the commutator only to determine position and then switch the fields with MOSFETS. There is now no current being switched so the arcing and EMI problems go away. Also since the brushes no loner have to be low resistance, they can be made from some conductive ceramic that will never wear out. I am not a motor expert but it seems this may be a good solution for the sub 1 HP motors. Comments? Opinions.

ALL CONTENT AND MATERIALS ON THIS SITE ARE PROVIDED "AS IS". CYPRESS SEMICONDUCTOR AND ITS RESPECTIVE SUPPLIERS MAKE NO REPRESENTATIONS ABOUT THE SUITABILITY OF THESE MATERIALS FOR ANY PURPOSE AND DISCLAIM ALL WARRANTIES AND CONDITIONS WITH REGARD TO THESE MATERIALS, INCLUDING BUT NOT LIMITED TO, ALL IMPLIED WARRANTIES AND CONDITIONS OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT OF ANY THIRD PARTY INTELLECTUAL PROPERTY RIGHT. NO LICENSE, EITHER EXPRESS OR IMPLIED, BY ESTOPPEL OR OTHERWISE, IS GRANTED BY CYPRESS SEMICONDUCTOR. USE OF THE INFORMATION ON THIS SITE MAY REQUIRE A LICENSE FROM A THIRD PARTY, OR A LICENSE FROM CYPRESS SEMICONDUCTOR.

Content on this site may contain or be subject to specific guidelines or limitations on use. All postings and use of the content on this site are subject to the Terms and Conditions of the site; third parties using this content agree to abide by any limitations or guidelines and to comply with the Terms and Conditions of this site. Cypress Semiconductor and its suppliers reserve the right to make corrections, deletions, modifications, enhancements, improvements and other changes to the content and materials, its products, programs and services at any time or to move or discontinue any content, products, programs, or services without notice.