The development and production of electric motors is becoming an increasingly attractive topic, which is why more and more news, websites and beautiful presentations appear on the Internet on “unparalleled” or “innovative” synchronous electric motors and permanent magnet electric drives. The bulk of such information is created by startups, which usually do not publish the technical characteristics of their developments, but are limited to some comparative assessments of their samples relative to abstract “analogues”. The reason is clear: after all, the development of a final competitive product requires large financial and engineering resources, which startups do not have, but really want to get. This forces them to go for a trick and wishful thinking. Even if something material is shown to a potential customer or investor, then it is, as a rule, a sample or prototype of an early stage of experimental design (R&D) or even research and development (R&D), which does not provide the declared characteristics or generally turns out to be inoperative.
How can one correctly compare electric motors and how to filter out information from charlatans and unscrupulous “startups”? …
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A short excursion into history.
The “confrontation” between synchronous and asynchronous electric motors began in the middle of the 20th century. At that time, the head of the “team of synchronous” was the so-called DC electric motor, it is also “collector”, it is also the simplest “member of the family” of synchronous electric machines. Why “simplest”? Due to the fact that, unlike a modern synchronous electric motor, it has a built-in primitive control system – a collector. This important detail helped to achieve the main thing: to create a simple and cheap synchronous machine that can be powered directly from a DC source. However, the drawbacks of the collector electric motors turned out to be much more than the advantages: the limited service life and low reliability, as well as the constructive limitation of the number of poles did not allow increasing the torque.
It was on the wave of the struggle with the problematic collector in the 80-90s of the last century that brushless asynchronous electric motors began to gain popularity. Despite the fact that it turned out to be more difficult to make the “asynchronous” technologically, and the efficiency and torque are significantly inferior to similar synchronous electric motors, “asynchronous motors” began to quickly displace the collector motors. At that time, brushless synchronous electric motors still did not have a chance, since there was still no available technological and element base for their manufacture and high-quality control. Because of this, some specialists and representatives of the older generation still have a persistent prejudice that synchronous electric motors are very expensive and difficult. Until affordable digital systems and new control algorithms were created, one of the main disadvantages of synchronous electric motors was the inability to control their speed.
Present day.
Synchronous electric motors of the EM-I series with efficiency reaching 97 – 98.5%.
Over the past 5-10 years, the prospects for synchronous electric machines have dramatically improved and expanded! With the beginning of the transition to the 6th Technological Layout, new production technologies, such as metal-plastics and heat-conducting composites, powder metallurgy and 3D printing, etc., become more and more accessible and widespread. Power semiconductors, specialized microcontrollers and other electronic element base have fallen in price many times and have improved their characteristics. New original solutions have been developed, allowing several times to increase the specific power characteristics of electrical machines. Thanks to the rapid development of modern frequency converters with digital control systems, synchronous electric motors have become easy to control. Accurate controllability of all power characteristics of synchronous drives in the entire operating speed range and high efficiency, both during acceleration and at idle, have become additional important advantages relative to asynchronous drives. Due to their design features, asynchronous electric motors are ineffective at idle and low speeds, continuously consuming energy to excite the rotor and requiring overcurrents for acceleration, which exceed the nominal values by 4-5 times! In comparison, synchronous motors deliver rated torque throughout the entire operating speed range at rated current. The lower operating current allows, in particular, the use of batteries with a higher specific capacity.
Higher efficiency and torque at relatively low operating currents and good controllability allow synchronous electric motors to successfully displace asynchronous ones in all types of electric transport: land, air and water. From such advanced industries as robotics, mechatronics and aircraft construction, asynchronous
