Although motors are a fundamental part of any motion system, selecting the right motor for an application is rarely an easy decision. There are various motor technologies to consider, and each has characteristics that can affect the design in different ways. Factors such as speed, torque, lifetime, mechanical envelope, accuracy and duty cycle will determine whether you choose a brushless DC, coreless DC or stepper motor.
Your motion system’s output speed requirement should be one of the first factors to consider when selecting your motor. Brushless DC motors are well-suited for higher speed operation. Coreless DC motors work well at moderate speeds. Higher speeds cause the brushes to wear, which can lead to a shorter lifetime. Stepper motors are electronically commutated, but their higher number of pole pairs makes them suitable to run at lower speeds.
Another factor to consider is the output torque requirement of your motion system. Engineers should focus on both the continuous torque for the application and the peak torque for a limited time during operation. Different motor technologies are characterized by different maximum continuous output torque capabilities. However, depending on the application, all three motor types may be capable of delivering the required output torque. Additionally, you may add a gearbox to increase your motion system’s output torque capability. Note that there is a corresponding reduction in output speed, according to the gear ratio.
The motion system’s work is typically defined in a number of cycles per day and time per cycle, or hours of operation per day and duty cycle. With this information, you can determine the maximum number of hours the motion system needs to operate over the anticipated product life. This prediction will influence your motor selection. Brushed DC motors have a mechanical commutation system that wears over time, limiting their lifetime, while brushless DC and stepper motors are electronically commutated and do not have any of the associated wear, giving them a longer expected lifetime.
Bearings also influence the lifetime of a motion system. Sleeve bearings will provide a few thousand hours of life, while ball bearings will generally provide more than 10,000 hours of life. Of course, the radial and axial loads applied to the motion system’s shaft must fall within specified design limits. Additionally, increased heat inside the system may adversely affect the lifetime of the lubricants.
To achieve your required mechanical envelope, you must first confirm that the motor technology you choose is available in a diameter and length that will fit in its intended space. While speed and torque requirements can often be met by one or more motor types, and even by variations within a given technology, you must also be certain that the motor’s power capabilities are sufficient for the application.
With respect to system accuracy, both brushed and brushless DC motors require an encoder to track and control the position of the rotor. Standard encoders offer a range of resolutions within the same package size to meet varying application requirements. You can also increase resolution by adding a gearbox to the front of the motor. The resolution is multiplied by the gear ratio, so you can achieve precise positioning by combining the encoder and gearbox multipliers.
Stepper motors are constructed to provide positioning accuracy. The number of poles on the rotor will dictate the number of steps per revolution, producing a step angle for each pulse given to the motor. Drivers typically can increase this resolution via half-stepping or micro-stepping, creating intermediate electrical steps between mechanical steps. An optional gearbox may also provide additional resolution based on the gear ratio.
Typically, the motor does not run continuously in an application. It usually operates for a period and rests for a period. When it comes to duty cycle, pay attention to the motor’s temperature rise. All motors have a maximum rated temperature. Operating the motor above that temperature can damage its internal components. The amount of current the motor draws will influence the temperature rise; the higher the current, the faster the temperature will increase.
Since current is proportional to the torque output of the motor, you may be inclined to increase the current to increase the torque, keeping the motor’s overall size as small as possible. Keep in mind, however, that the on-time requirements for the cycle have to be balanced so the current drawn doesn’t cause the motor to exceed its maximum operating temperature.
Finally, don’t forget about environmental factors that may affect duty cycle. Will the motor be mounted to a base that can conduct heat away? Is there enough air flow around the motor to help keep it cool? Will the motor be housed inside an enclosure among heat-generating components that will raise the ambient temperature?
If the product will be in a fixed location, you’ll have greater flexibility in regard to a motor’s size and weight. You can focus more on the performance characteristics you need for your application. For battery-powered mobile or ambulatory products, the motor’s current draw is critical. The lower the current draw—while the motor meets its performance requirements—the longer the battery can run between charges. Be sure to prioritize motor size and weight for battery-powered devices.
Every application presents many factors to consider during motor selection. When determining the most suitable motor technology for your application, you must carefully weigh all the factors and decide how they will affect motor performance so you can develop an optimal product.
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Maintaining industrial and commercial machinery requires many tasks. One of the most significant responsibilities is inspecting, maintaining and repairing electrical motors. You need to ensure facility tools meet safety standards and efficiency requirements, and choosing a suitable electric motor is a key part of that job.
Electric motors power numerous industrial and commercial applications and support many functions, like powering machine compressors, pumps and tools.
However, not all electric motors are equal, and some suit specific applications better than others. Considering factors like speed, torque, duty cycle, load compatibility and maintenance requirements can help you select a compatible electric motor for your industrial facility.
Suitable torque is necessary for driving electric motor startup and acceleration speeds. Applications require varying amounts of force to start up and accelerate load to a specific rate in a set time. You’ll need to consider a piece of equipment’s torque requirements when choosing an electric motor to ensure it can operate without excessive strain.
Your electric motor’s output speed must be compatible with your needs. Some electric motors suit high-speed applications, while others are better for moderate- to low-speed processes. Your application might also require adjustable controls that accommodate specific increments. Understanding different motor designs and output capabilities is vital for selecting a suitable range for your applications:
Do you need an AC or DC motor? Selecting a suitable power source is vital for running your equipment effectively. DC motors allow for fine speed control since their rpm output is directly affected by the amount of voltage supplied. AC motors require a variable frequency drive for speed variation but offer greater efficiency. An AC motor tends to excel in low- to medium-speed operations, while DC performs better when higher speeds are needed.
Does the motor offer different speed ranges and control settings? Some applications require a definite operating speed, while others need adjustable rates. You can add a controller or drive to your DC or AC electric motor to manage torque and rotation. A controller can also regulate different application speeds, weights and loads.
The motor’s operating lifetime determines the life span of a product or tool. Consider how long you’ll need the motor to last and how much time and money you plan to put into maintaining it. Brushless DC and stepper motors have fewer wear components and tend to last longer, while brushed DC motors deteriorate more quickly.
The duty cycle determines how long the motor can run over production cycles. You might run applications continuously or over short periods. A longer run time will require a motor with a higher duty cycle to ensure you don’t lose power. You can use a smaller motor if you only need it intermittently and it will have enough rest time to return to ambient temperature.
The environmental temperature will affect a motor’s duty cycle, as the objective behind limiting run time is preventing overheating and any resulting damage.
The enclosure ranking depends on the conditions a motor must operate under. Consider the environment surrounding the installation — will the motor be exposed to moisture, dirt, debris or extreme heat? Neglecting to provide proper protection during installation is one of the most common causes of motor failure.
You’ll need suitable protection for your motor depending on your working conditions. For example, food and beverage industries might need stainless steel castings to protect machinery motors from spills, corrosion and wear.
Some electric motors can run on batteries or a power outlet. Depending on the facility, you’ll need to decide if you’ll connect a motor to the power grid, inverter or batteries. The voltage must be compatible with your motor if you use a wall socket or outlet. Smaller tools and lower power applications can use standard voltage, but you will likely need to draw more power for industrial motors.
Depending on your working conditions, a motor can require climate protection. Consider the temperature of the facility. Is it a hot or cold environment? Understanding the climate will help you select a motor with suitable materials or coverings.
Some applications require both backward and forward rotation. Some motors do not have multiple reverse or rotation capabilities, so be sure to choose a motor that can do everything your tasks require.
Electric motor capacity and size will impact operational efficiency. An electric motor must offer sufficient torque for your application’s load without generating more heat than the insulation present can handle.
A key factor in selecting motor size is whether you will be installing it permanently or in a system you plan to move often. You can get a bigger motor for equipment that will remain in one place, like a large lathe in an industrial building. Anything you need to transport often will call for careful consideration.
Whether noise is a concern will depend on where you’re using the motor. You might select a model geared for noise reduction if the installation will be in a public area like a hospital.
Motors have different maintenance requirements. Consider the motor type and if you can maintain and repair it yourself or need professional services. DC motors tend to be more challenging to maintain and require expert knowledge.
Having a way to collect data on motor performance can enhance your applications. With encoders or sensors, you can get feedback on how well the motor works and adjust speed and other settings for better performance. Data components offer diagnostic capabilities to indicate wear or damage so you can schedule maintenance, preventing breakdowns and downtime.
A motor’s operating costs depend on its life span, maintenance requirements and initial price. You’ll need to decide which model will offer the best value for your money or return on investment. Weighing potential costs is necessary before selecting an electric motor for your commercial facility.
Deciding on an electric motor for your industrial or commercial facility requires you to look at many complex factors. If you want to ensure you select the best model based on your unique circumstances, it’s best to consult a professional. Industrial Electrical Company specializes in various electric motor services, including installations, preventive maintenance and repairs.
Our certified technicians are experts in their craft. We’re also committed to delivering exceptional customer service, and we’ll answer your calls 24 hours a day. Whether you want us to evaluate trouble signs with an existing motor or assess your requirements and help you choose a new model, our team will make sure you have everything you need.
Contact us to learn more about our electric motor services.