In today’s industry, where the highest quality standards apply, it is only the right choice of electric motors that enables mechatronic systems to function as intended. Developers should exercise particular care when selecting electric motors, as the chosen technology will not only define the system’s technical characteristics but also its maintenance requirements, energy efficiency, and ultimately, the operating costs throughout the product’s lifecycle.
The Three Main Categories of Electric Motors
In industrial practice, developers are typically faced with choosing between three proven technologies in the field of electric motors, each of which has established itself across various areas of application. Stepper motors are among the most precise electric motors and have proven particularly valuable in precision industries. These motors are characterised by their ability to achieve precise positioning without the need for additional sensors, enabling smooth control at low speeds.
Brushless DC motors (BLDC) are highly efficient electric motors, primarily used in high-end industrial applications. These motors offer higher efficiency and a longer service life than brushed DC motors, but typically operate at higher speeds and often require a gearbox for applications needing low speeds and high torque.
Brushed DC motors are the most cost-effective type of electric motors and are mainly used in price-sensitive applications where operating times are limited. Due to brush wear, these motors have a limited service life and are therefore only suitable for specific use cases.
Practical Example: Selecting Electric Motors for an Infusion Pump
A practical example of selecting electric motors can be found in the development of a dosing unit for infusion pumps. The developers faced the challenge of selecting from various electric motors the one that could deliver the highest precision, compact size, and absolute reliability.
Following an in-depth analysis of different motor types, the engineers opted for a stepper motor. This decision was based on several key factors: the stepper motor allowed the infusion pump to be built lighter and more compact than its predecessor. With a target weight of only 1.4 kilograms, the new model was intended to be 15 per cent lighter than its predecessor.
The chosen stepper motor, from the category of electric motors, guarantees precise and smooth control in the speed range of 0 to 500 revolutions per minute – a level of precision that meets the highest quality standards. These properties make stepper motors particularly valuable for applications in medical technology and precision mechanics.
Why Not BLDC or DC Motors? The Decision in Electric Motors
The developers certainly considered other types of electric motors. BLDC motors fundamentally offer high efficiency and long service life – qualities highly valued in modern electric motors. However, BLDC motors typically operate at higher speeds and deliver lower torque.
To achieve comparable speed and torque, these motors would require reduction through a gearbox. Although BLDC motors can indeed be combined with specialised gear units, this particular application focused on reducing overall weight.
Brushed DC motors would certainly have been more attractive from a cost perspective, but they too would have required a gearbox. Additionally, a decisive factor ruled out these motors: their limited service life.
Service Life: A Critical Criterion for Electric Motors
Service life, alongside speed and physical size, was another critical criterion in selecting electric motors. In clinical practice, infusion pumps often operate continuously for several days, where motor failures are not only costly but potentially dangerous.
This high utilisation frequency immediately ruled out brushed DC motors. With a typical service life of only a few thousand hours, these motors would not last even a year in continuous operation. The selected stepper motor offers a significantly better alternative, with a typical lifespan of over 20,000 hours.
Gearboxes and Couplings in Electric Motors
When selecting electric motors, developers must also carefully consider the impact of gearboxes and couplings. A gearbox always introduces some degree of play into the system – a factor that must be critically examined in applications requiring precise motors.
For applications that demand absolute freedom from backlash, as is required with high-quality electric motors, there is no alternative to a direct-drive solution. The amount of play a gearbox introduces into a system also depends on its design. A worm gearbox, for example, typically exhibits less play than a planetary gearbox.
A Decision-Making Aid for Selecting Electric Motors
When selecting the optimal electric motors for a specific application, developers should undertake a systematic evaluation based on the following criteria: precision and quality, service life and maintenance, energy efficiency, and total cost of ownership.
Stepper motors are particularly suitable for applications requiring the highest levels of precision. For continuous operation, stepper motors or BLDC motors are often the more economical choice. In environmentally conscious markets, energy consumption is becoming an increasingly important factor in electric motor selection.
Conclusion: Systematic Selection of Electric Motors
Selecting the ideal electric motors requires careful consideration of all relevant factors. There is no such thing as “the best” electric motor – only the most suitable one for a specific application. The example of the infusion pump demonstrates how a systematic evaluation of different electric motors can lead to a well-informed decision.
When selecting electric motors, developers should not only focus on the obvious parameters but also consider factors such as service life, maintenance requirements, and the impact on the overall system design.
Do You Need Support in Selecting Electric Motors for Your Project?
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