Motors are a ubiquitous presence today in all applications, from toys to the military. Similarly, motors come in various types such as heavy-duty AC motors to tiny DC brushless and stepper motors. Matching the right type of motor with the suitable application is the key.
Motor selection for an application is influenced by a number of factors such as including power, speed, torque, physical size, efficiency, duty cycle, ambient temperature and specific application parameters such as controlled feedback, brake, the desired result and the working environment.
Factors that influence the selection of DC motors
Input power
Take a note of the available input voltage at the terminal of the motor, current limits, and what controls will be required to manage the motor within the application. Pay close attention to the maximum allowable current early in your selection process. This is often overlooked until the testing phase when failures can occur.
The current and efficiency of the motor can be changed by the style of the gearbox, input power, or other factors. Using a more efficient gearbox means you draw less current to run the motor.
The measure of available voltage is a key criterion in the selection of DC motors. Most devices today are portable and battery-operated. DC motors of various sizes and capacities can operate in the range of 6V to 220V. Hence, the amount of available as well as required power must be considered when selecting a DC motor.
Motor size
Technological development in the modern world is focused on reducing the footprint of machines. Most of the devices around us are rapidly shrinking in size. It is vital that the motor fits the available size within the device. Even as the size is being reduced, motors must deliver the best possible efficiency. Here, the power consumption of the motor also comes into the picture. Diameter of the motor is in square proportion to the torque and length of the motor is in linear proportion to the torque.
Torque and speed
The torque and speed of the motor have a bearing on the motor frame size. If the size of the motor is small, it will deliver lower torque. If higher torque is required, larger housing for the motor is an important requirement. For instance, rolling an automobile window will require a smaller motor whereas rotating the magnets of MRI scan will need a far bigger one.
Assuming that the voltage stays the same, the torque of the DC motor is inversely proportional to the speed. This connection is based on the slope of the speed/torque curve.
Duty cycle
The motor duty cycle is critical to determining the motor type as well as the service life of the motor in use. Operating time, dwell time, and rotational direction are key aspects of the DC motor duty cycle. In the case of most industrial applications, motors are operated intermittently as it helps extend the service life of the motors.
The duty cycle is also influenced by the motor size. If the motor needs to run periodically, a shorter motor would be able to introduce as much power as a larger motor running continuously. This is because the off-time for the intermittent duty motor allows for the release of excess heat. If used in this manner, smaller motors can be used for a long duration without depleting the positive characteristics of the machine itself.
Working conditions
Particle ingress and temperature are two major environmental constraints impacting motor performance. Most standard motors are built to operate in a clean, dry room temperature environment. However, in areas such as solar energy or defense, motors must operate amidst temperature extremes, dust, or corrosive environments. In such cases, a specially constructed motor should be considered.
IP ratings provide an industry-wide understanding of a motor’s protection against dust and water. The same is the case with temperature class ratings. For every 10 degrees of temperature your application exceeds the maximum temperature rating, the motor life is reduced by 50%.
Brushed or brushless motors?
When to use a brushless motor?
Brushless DC motors last longer and work faster but will require a electronics connection to power them. Additionally, brushless motors cannot be used with a gearhead because it will reduce the lifecycle of the combined system, and ultimately reduce the lifespan of the machine the system is supposed to operate. Even so, in certain rare circumstances, a brushless motor can be used with a gear box. Such scenarios include working conditions where a high noise level can be allowed or areas where higher torque is required.
When to use a brushed motor?
Brushed motors do not need additional electronics to run. Hence, they offer a plug-and-play option. The lack of electronics saves considerable costs. Brushed motors can work with gearheads, and their lifespan is not affected by the same. Both the motor and the gearhead are mechanical components that witness a high degree of wear and tear. They offer high starting torque.
Power requirements of the motor
A major aspect to consider here is the power requirement of the DC motors. DC motors are available in a wide range of power ratings in both brushed and brushless categories. Before choosing the type of DC motor, users should identify the power requirement of motors for their applications.
Work with experts in custom DC motors
DC motors are a small yet critical component of many industrial machine systems. Failure of the DC motor at a critical juncture could mean significant financial loss and downtime. Working closely with an experienced motor manufacturing expert could ensure the availability of best suitable, durable, and reliable motors for your application.
Pranshu Electricals offers custom motors that deliver the desired speed and torque while performing consistently in rugged conditions. Apart from the customization as per customer requirements, Pranshu motors come with a special powder coated body, special brush holders and brushes and stainless-steel shaft* which offers a longer lifespan than many other conventional motors.
*Stainless steel shaft is offered in special requirements at additional cost.
