Which is More Efficient: Brushless or Brushed Motors?

Efficiency Comparison Between Brushless and Brushed Motors

When selecting a motor, efficiency is one of the key metrics for measuring performance. Due to differences in technical principles and structural designs, brushless motors (BLDC) and brushed motors exhibit distinct efficiencies.

Brushed Motor: Mechanical Commutation Leads to Energy Loss

Brushed motors rely on brushes and a commutator to achieve current commutation. During operation, the brushes continuously rub against the commutator, generating heat and causing electrical energy loss. Additionally, sparks produced by friction result in some electrical energy being lost as heat, further reducing motor efficiency. Over time, brush wear increases contact resistance, leading to a continuous decline in the efficiency of converting electrical energy into mechanical energy.

Generally, the efficiency of brushed motors ranges between 70% and 85%, with efficiency decreasing even more at high speeds or during prolonged operation.

Brushless Motor: Electronic Commutation Achieves Efficient Operation

Brushless motors use an electronic commutation system instead of mechanical commutation. Hall sensors detect the rotor's position, allowing electronic circuits to precisely control the direction of current flow, avoiding energy losses caused by brush friction.

Without mechanical contact components, the energy loss in brushless motors mainly comes from winding resistance and hysteresis losses, which are relatively small. Moreover, electronic commutation can adjust the current in real-time according to load changes, enabling the motor to maintain high efficiency under various operating conditions. Thus, the efficiency of brushless motors typically ranges from 85% to 95%, making them superior in terms of energy savings.

The mechanical commutation structure of brushed motors leads to inherent drawbacks. Long-term friction between brushes and commutators not only reduces efficiency but also generates carbon dust and other pollutants, affecting internal cleanliness, heat dissipation, and operational stability, thereby indirectly lowering efficiency.

In contrast, the design of brushless motors is more compact and reasonable, lacking easily worn mechanical commutation parts. They operate with minimal vibration and noise, resulting in a smoother energy conversion process that converts more electrical energy into mechanical energy, naturally achieving higher efficiency.

In scenarios requiring frequent start-stop cycles and precise speed adjustment, such as industrial robots and automated production lines, the efficiency advantages of brushless motors are particularly evident. Their electronic commutation systems can quickly respond to control signals, maintaining efficient operation at various speeds. In comparison, brushed motors suffer from significant efficiency fluctuations during frequent speed adjustments due to limitations in mechanical commutation, failing to meet the demands for high precision and efficiency in production.

In household devices like fans and electric shavers, brushed motors are still widely used due to their low cost and simple structure. Although their efficiency is relatively lower, the impact on overall energy consumption is not significant given the smaller power ratings and shorter usage times. However, in larger household appliances with higher energy-saving requirements, such as high-end refrigerators and air conditioner compressors, brushless motors are gradually becoming mainstream choices due to their high efficiency.

For outdoor mobile devices like drones and electric bicycles, battery life is crucial. The high efficiency of brushless motors reduces energy consumption and extends device usage time. For instance, drones equipped with brushless motors have 20% to 30% longer flight times compared to those using brushed motors, which is significant for devices needing to perform long-duration tasks.

Overall, brushless motors generally have higher efficiency than brushed motors, primarily due to electronic commutation technology and superior structural design. However, in practical applications, the choice between the two should be based on specific needs. If high efficiency, longevity, and low maintenance are priorities, brushless motors are the better choice. On the other hand, if cost is a primary concern and efficiency requirements are not stringent, brushed motors can still meet the needs of certain scenarios.