Abstract: This article introduces a patented technology of the author. For applications requiring rapid and frequent frequency adjustments, current general-purpose inverters struggle to meet this need, especially when using inverters with large inertia loads. In such cases, the speed of frequency increase and decrease (particularly decrease) must be set relatively slowly to accommodate the lag in motor speed caused by inertia. This patented technology overcomes these shortcomings of traditional inverters by adding a simple and mature commutation technology to the traditional inverter, providing a new and additional technology for inverter manufacturing. The patented technology overcomes the aforementioned defects with simple yet mature phase-changing technology, becoming a new and additional technology for inverter manufacturing. Keywords: Inverter, High-inertia load, Phase sequence switching. 1. Introduction Currently, inverters are widely used in production processes requiring adjustment of operating conditions and energy saving. Inverters play a significant role in facilitating motor condition adjustment and saving energy. In today's and tomorrow's increasingly energy-scarce world, where the establishment of an energy-saving society is imperative, inverters will see even wider applications. If users require rapid and frequent frequency adjustments when using inverters, traditional inverters are insufficient, especially when using inverters on loads with high inertia. In such cases, the frequency ramp-up and ramp-down (especially ramp-down) speeds must be set relatively slowly to accommodate the lag in motor speed caused by inertia. Because of inertia, the synchronization between the motor and its load speed and the inverter's output frequency requires a certain amount of time, especially for loads with high inertia, where this time is relatively long. If the frequency adjustment speed is much faster than the motor speed, the motor will operate in a generator state within four quadrants. Industry professionals know that this generator state is very dangerous for the frequency converter. Traditional frequency converters address this problem by installing a discharge protection circuit. However, even with this circuit, it only protects the frequency converter from malfunction; it doesn't truly solve the inertia problem of the motor and its load. This is because traditional frequency converters are merely devices that adjust the frequency and voltage of the output power; they don't constrain the motor's inertia. The lack of inertia control in traditional frequency converters makes them inconvenient, unsafe, and unreliable in certain situations, effectively limiting their application range. Mechanical methods obviously cannot effectively synchronize the controlled motor; while traditional electric braking can be performed simultaneously with frequency conversion, it's very difficult to synchronize the controlled motor's speed with the frequency conversion process, as traditional electric braking is primarily for braking. This is the main reason why adjusting the speed of a controlled asynchronous motor using a frequency converter is not as effective as adjusting the speed of a DC motor. The author of this paper has developed a unique approach to electric braking, which effectively controls the speed of a controlled motor and quickly synchronizes it with the frequency of the inverter's output power. This braking method assists the inverter in adjusting the motor's speed, maximizing the adaptation to the inertia of the motor and its load. It synchronizes the motor's speed with the inverter's output power frequency in the shortest possible time, protecting the inverter and enabling it to adapt to loads requiring rapid and frequent frequency adjustments and high inertia, thus expanding the application range of high and low voltage inverters. The motor speed braking device in this method can also be used independently as a soft starter for motors and as a speed control device in applications requiring frequent frequency adjustments, precise braking, or even reverse operation. When used as a speed control device, the speed control effect is comparable to that of a DC motor. 2. Principles for Improving the Dynamic Response of Frequency Converter Frequency Adjustment Speed This project aims to overcome the shortcomings of traditional frequency converters by adding a relatively simple and mature commutation technology to the traditional frequency converter, providing a new additional technology for frequency converter manufacturing. This research is based on the principle that three-phase alternating current can form multiple phase sequences with phase differences between each other. The principle is as follows: the three-phase alternating current is A-phase, B-phase, and C-phase. Arranging the three-phase alternating current in different orders produces three forward sequences: A, B, C; C, A, B; B, C, A; and three reverse sequences: A, C, B; B, A, C; C, B, A. The three forward-sequence arrangements all have the same direction of rotation, but differ in phase. For a symmetrical three-phase AC circuit, these three forward-sequence arrangements differ in phase by 120°. The three reverse-sequence arrangements are similar to the three forward-sequence arrangements, with the motor rotating in the same direction (but opposite to the forward-sequence arrangements), and differ in phase by 120°. If the order of the three input lines of the stator of the controlled three-phase asynchronous motor is fixed, and they are switched in a certain regular and periodic sequence between the three forward-sequence arrangements (or between forward and reverse-sequence arrangements), the stator rotating magnetic field lags behind by 120° after each switch due to the 120° phase difference between the three forward-sequence arrangements (in the case of switching between forward and reverse-sequence arrangements, it is the opposite). This creates a regenerative braking state where the rotor magnetic field pulls the stator magnetic field, i.e., a regenerative braking state. If these switches are performed at a certain frequency, the motor will operate in an alternating state of motoring and regenerative braking: in the motoring state, the slip S > 0, and in the regenerative braking state, the slip S < 0. Regenerative braking is essentially "braking," which causes the rotor to be frequently "braked" during rotation, naturally slowing down its speed. The higher the frequency of phase sequence switching, the more times the stator rotating magnetic field lags ("braking") per unit time, resulting in a lower rotor speed; conversely, the lower the frequency of phase sequence switching, the fewer times the stator rotating magnetic field lags ("braking") per unit time, resulting in a higher rotor speed. When the phase sequence switching frequency is "0," i.e., no switching occurs, the rotor speed is the highest, which is the rated speed of the motor. Of course, if the order of the three input lines of the three-phase asynchronous motor stator is fixed and they are switched in three reverse order arrangements according to a certain pattern and cycle, the lag in the stator rotating magnetic field can also be caused, thus changing the rotor speed, only in the opposite direction. The specific working principle of the motor speed braking device for quickly adjusting the inverter's control of motor speed is as follows: a switching synchronization circuit (including a target frequency retrieval circuit and an instruction selection circuit), a switching controller (including an instruction memory and an instruction issuing circuit), a switching control circuit, and a switching switch are installed on a traditional inverter. When the frequency converter is not adjusting the frequency or the frequency adjustment is completed (i.e., the current operating frequency has reached the target frequency), the instruction selection circuit does not receive instructions from the target frequency retrieval circuit (or receives instructions not to perform phase sequence switching), and the instruction issuing circuit does not issue a switching instruction. The drive signal output by the switching control circuit enables the motor to run normally and at a constant speed according to the frequency of the electrical energy output by the frequency converter at this time. When the frequency converter issues a frequency adjustment instruction (i.e., the target frequency is different from the current operating frequency), the target frequency retrieval circuit retrieves the new target frequency instruction (if a retrieval function for the difference between the current operating frequency and the target frequency is configured, it will also retrieve the difference between the current frequency and the new target frequency), and immediately issues a corresponding selection instruction to the instruction selection circuit. The instruction selection circuit selects the corresponding switching instruction from the instruction memory and issues the corresponding phase sequence switching frequency instruction to the switching control circuit through the instruction issuing circuit. During the entire frequency adjustment process (i.e., before the current operating frequency reaches the target frequency), the phase sequence switching continues at a certain frequency until the frequency adjustment process ends (i.e., the current operating frequency is consistent with the target frequency), at which point the phase sequence switching stops. Thus, with the assistance of the phase sequence switching function, the motor rotor is braked by the phase change of the stator rotating magnetic field, enabling the motor speed to quickly match the frequency of the electrical energy output by the frequency converter, achieving the goal of rapidly adjusting the motor speed. It must be pointed out here that the example in this article uses the current operating frequency and target frequency of the frequency converter during the frequency adjustment process as the information source. During manufacturing and on-site debugging, it is best to also detect the motor speed during the frequency adjustment process to accurately determine the correspondence between the phase sequence switching frequency and the frequency adjustment process. Of course, if vector detection of the motor speed is added during the design and used as an auxiliary information source for phase sequence switching frequency and frequency adjustment, the effect will be better, but it will increase manufacturing costs. If the aforementioned motor speed braking device is used independently—that is, by configuring the instruction selection circuit, switching controller (including instruction memory and instruction issuing circuit), switching control circuit, and switching switch with an operator and interface to manufacture an independent control device, and pre-store the corresponding instructions in the instruction memory—it can serve as a soft starter for the motor, and also as a motor speed control device for applications requiring frequent frequency adjustments, precise braking, and reverse operation. However, since there are currently no semiconductor switching devices that can withstand high voltage (6kV, 10kV) and be used independently in high-voltage environments, the following methods must be adopted when using the phase sequence switching function to assist in the speed regulation of high-voltage motors: (1) Connect multiple semiconductor switching devices in series with the assistance of a parallel synchronous protection circuit to enable them to withstand high voltage and achieve phase sequence switching; (2) Add a phase sequence switching function to the frequency program of the high-voltage inverter and realize phase sequence switching in the waveform generation stage. This only requires adding a corresponding phase sequence switching program to the original control program, without the need for hardware addition or modification. This is a relatively safe and reliable method; (3) Once there are semiconductor switching devices that can withstand high voltage (6kV, 10kV) and be used independently in high-voltage environments, the semiconductor switching devices should be used directly to realize phase sequence switching. Since the motor may generate energy during braking, an energy absorption and discharge circuit should also be set up to protect the inverter in the frequency adjustment program. Of course, it would be even better if an energy feedback circuit were installed to feed the energy generated by the motor during braking back to the preceding circuit for further utilization, thus further improving the energy-saving effect. 3. Conclusion The technology introduced in this article has been patented. It overcomes the shortcomings of traditional frequency converters by simply adding a relatively simple and mature commutation technology to them, providing a new and additional technology for frequency converter manufacturing, and also expanding the application range of frequency converters.