Brush DC motors have been around for more than 100 years, and is a pivotal piece of technology that paved the way for the easy conversion of electrical energy into mechanical energy. And while they do have a lot of advantages, including and especially their low construction costs, one of the most glaring disadvantages of brush DC motors is the wear and tear of the brushes. Depending on the level of usage, the brushes of these motors require replacement after every 2,000 to 5,000 hours of operation. Because of this downside, brushless DC motors have slowly replaced their brush counterparts in several applications.
Nonetheless, high technology brush motors are still being manufactured and used in bulk today, even with the emergence of newer technology. Here are a few reasons behind this.
The simplicity of brush DC motors is one of the main reasons why they’re still so popular. They can be wired directly to a DC power source and the most basic of switches can already serve as their speed controllers. This is because brush DC motors can have a linear torque-speed relationship, where low speed gives high torque and high speed gives low torque. In fact, if the application doesn’t require variable speeds, there is no need for controllers at all.
They Have a Wider User Base
Brush DC motors are a mature, some would even say old, technology, with the earliest iterations being invented and commercially implemented in the mid to late 1800s, compared to the much younger technology of brushless DC motors (around 1967) and AC motors and inverters (around 1987). This means that there are significantly more pieces of machinery that are still using DC motors today and, therefore, more engineers, machine manufacturers and operators, and maintenance personnel have more knowledge of the workings of DC motors.
They Continue to Improve
Brush DC motors may be old, but that doesn’t mean that research and development have stopped for them. The focus of R&D in brush DC motors are the commutator and the brushes, which are their most maintenance-extensive parts. One particular breakthrough is that in the pursuit of increasing power density, the commutator size has gotten considerably smaller in the process. This means that there is less friction and thereby less brush wear with each turn of the rotor. Some engineers have also redesigned other elements of DC motors such as the pressure fingers, which creates space for longer brushes. This further extends the interval between brush changes.
More recent developments include brush wear sensors, which can be purchased along with the motors. These sensors detect the level of wear and tear of the brushes, which then alert the maintenance staff that it’s time for the routine replacement. Apart from giving timely reminders to the maintenance and procurement staff that a service procedure is due, the sensors also help prevent the commutator from being damaged by a worn brush.
They are More Affordable
As earlier mentioned, brush DC motors cost less than both their brushless counterparts and AC motors and inverters. The cost goes down even more when they are produced in large volumes. What’s more, the repair and maintenance costs of brush DC motors are still relatively lower than the initial cost of buying or converting to brushless or AC.
Therefore, using brush DC motors in applications that are designed to have a limited lifespan or a long lifespan but with moderate or controlled usage cycles — such as motorized components of vehicles or high-end appliances like super blenders — also makes these applications more affordable for consumers.
This is not to say that brushless DC motors or AC motors are in any way sub-par. In fact, there are many applications where these two motors are the more appropriate choices, such as those that require quieter operations or frequent reverse rotations. However, brush DC motors’ usefulness and various applications are not to be dismissed, even in today’s modern world where everyone is excited to use everything new.