Abstract : This paper introduces the characteristics and application fields of synchronous operation power frequency brushless speed-regulating motors. Keywords : Synchronization; Power frequency speed-regulating motor 1 Introduction As is well known, DC motor speed regulation relies on voltage or magnetism adjustment. AC motors, including synchronous and asynchronous motors, require both frequency and voltage regulation for speed regulation. In today's highly developed electronic technology, frequency converters are typically used. The capacity of a frequency converter is generally 1.3 to 1.36 times the motor frequency. The price of a frequency converter is often many times that of the motor, especially for high-voltage, high-power frequency converters, which can cost 7-8 times more than the motor. Of course, these frequency converters can meet the speed regulation requirements of the motor from 0 to 100%. However, in many industrial production fields, speed regulation from 0 to 100% is not required; sometimes, adjusting from around 70% to 100% is sufficient. For example, wire rod continuous rolling mills and hot strip continuous rolling mills only require speed regulation within ±10% of the production process. For energy-saving purposes, pumps and fans only need speed regulation from 100% to 70%. Furthermore, the power supply voltage for large and medium-sized motors is often high-voltage (10kV, 6kV, and 3kV). All types of high- and medium-voltage frequency converters are technically expensive. Therefore, this paper proposes a speed regulation method that, in situations where the speed regulation range is not wide, only low-voltage, low-power frequency converters can meet the speed regulation requirements of medium- and high-voltage, high-power motors. In fact, this idea was proposed as early as the 1940s, but due to the lack of suitable adjustable frequency converters and control systems based on microelectronics technology at that time, the excellent performance of AC-excited power frequency synchronous motors could not be utilized. Since the early 1970s, with the development of power electronics and microelectronics technologies, the engineering application of AC excitation generators has begun. Based on this, this paper proposes a synchronous operation power frequency brushless speed-regulating motor. 2. Differences and similarities with traditional synchronous motors (1) Traditional synchronous or asynchronous motors are powered by frequency converters with a capacity greater than the motor power. However, the frequency converter of this AC excitation synchronous operation only provides the following two parts of power through the exciter: a) the excitation power of the high-voltage power frequency motor; b) half of the power of the variable speed part of the high-voltage power frequency motor. The exciter is powered by a frequency converter with a smaller power. For example, when the speed of a motor is adjusted from 100% to 70%, when this scheme is used, 85% of the shaft output power is directly powered by the high-voltage power frequency, and only a maximum of 15% of the power is powered by the frequency converter. That is, the rated output power of the frequency converter only needs to be 15% of the rated power of the motor plus the power required by the excitation part. Moreover, the frequency converter voltage only needs to be conventional low voltage. For high-voltage, high-power motors operating at industrial frequencies, the vast majority of power is supplied by the high-voltage industrial frequency grid, significantly reducing the cost of expensive frequency converters. [b][align=center]For more details, please click: Synchronized Industrial Frequency Speed-Regulating Motors[/align][/b]