Your Top 3 Motor Application Questions — Answered
By Allied Motion | Apr 09, 2015
Whether you work for a large company and need a motor for a mass-market product, or you’re the guy next door designing the next big thing, there are many design factors to consider when choosing a motor for your project. You may be wondering if it can be done, where to begin or whom to call.
To help you begin, we sat down with Allied Motion application engineer, Jake Freeman, and asked him to answer your top 3 motor application questions.
What are the benefits of a brushless DC motor compared to a brushed DC motor?
Jake: The three greatest benefits of an Allied Motion brushless DC motor are:
- Extended life;
- Increased power density; and
- Increased efficiency.
A brushless motor commutates electronically, so its brushes are not used to generate motion in the motor. In a traditional brushed permanent magnet DC motor, the brushes are the first component to wear out from mechanical and electrical degradation. The absence of brushes greatly extends the life of a brushless DC motor when compared to a brushed DC motor.
We use rare earth magnets in the majority of our brushless DC motor designs, which greatly increase their power density in comparison to industry standard brushed DC motors. Brushless motors also have great thermal dissipation properties because they are designed with the stator on the outside of the motor. This greater thermal dissipation allows for higher continuous output power in comparison to a similarly sized brushed motor.
Also, since there are no brushes in the design, brushless DC motors eliminate the inherent frictional losses associated with typical brushed motor designs, which increases efficiency.
What information is necessary to size a DC motor for an application?
Jake: To accurately size a DC motor for a given application, our engineers need to know the voltage, speed/torque point, ambient temperature and duty cycle.
- Voltage. Knowing what nominal voltage, or voltages, is available in the system is vital in properly sizing a motor to the application. This information is necessary to determine input power.
- Speed/Torque Point. All applications require a certain speed (RPM) at a certain torque (N-m). This information is typically supplied by our customers and allows application engineers at the Solution Center to propose a motor that meets those requirements.
- Ambient Temperature. The ambient temperature of the motor’s environment is also important. All Allied Motion nominal performance specifications are recorded in an ambient temperature of 23°C, unless we state otherwise. The nominal motor performance must be de-rated with any increase in ambient temperature.
- Duty Cycle. An application engineer needs to know the duty cycle of an application to avoid under- or over-sizing a motor for that application. A complete load profile of speed and torque in relation to time is the best information to understand a duty cycle. Many applications involve a continuous speed and torque; these are referred to as “continuous-duty” applications.
What is the difference between a housed DC motor and a frameless DC motor?
Jake: Allied Motion offers both housed and frameless DC motors. Housed DC motors are designed as a single assembly motor while frameless motors consist of two individual parts: a stator assembly and a rotor assembly.
In the design of a housed DC motor, a stator assembly is encapsulated by a shell with one or two endplates holding the rotor assembly. This rotor assembly consists of a rotor, shaft and bearings in place. A housed motor is the “classic" motor design, and allows for simple installation of a single assembly.
In the frameless DC motor design, the stator assembly and rotor assembly are not mechanically coupled. This design allows for the customer to fully incorporate Allied Motion’s motor into their design. The customer can directly integrate a shaft and bearing system into the rotor assembly of a frameless motor without the need for an external coupling. The stator may also be assembled directly into the customer’s existing housing, eliminating excess material. Frameless motors are also useful when weight and packaging size constraints exist.
For answers to all of your motor application questions, please contact an Allied Motion Solution Center:
❯ North America: 1-888-392-5543
❯ Europe: +46 (8) 546 111 00
❯ Asia: +852 2607 4038.