1. Introduction In the 1980s, soft starters became the ideal product for motor starting control. However, they all operated with thyristors online, resulting in very high costs and power consumption, leading to a severe imbalance between cost and technology and making them difficult for users to accept, resulting in very few applications. However, the alternative of bypass-operation soft starters significantly reduced the cost of soft starting systems, making their cost-effectiveness superior to other starting methods, reaching a level easily accepted by users. Furthermore, my technical lectures at various design institutes and industrial enterprises promoted the widespread adoption of soft starters in engineering applications. 2. Analysis of Soft Starter Types 2.1 Thyristor Online Operation Soft Starters Thyristor online operation soft starters (referred to as motor controllers) refer to soft starters where the main switching element, the thyristor, operates continuously online. It not only controls the voltage rise and fall of the motor during starting and stopping but also supplies the full voltage to the motor during normal operation, as shown in Figure 1. Its advantages include simple circuitry, flexible control, and strong protection for the motor. Its disadvantages include the online operation of the thyristors, resulting in extremely high power consumption of the soft starter itself. To address the heat generated by this power consumption, the soft starter body is designed to be very large, and mechanical cooling is also required. If a distribution room has ten 200kW motor soft starters, firstly, these ten soft starters alone would require ten switch cabinets, significantly increasing the floor space. Secondly, their heat output would reach approximately 15kW. Under such circumstances, regardless of winter or summer, the room temperature would exceed the standard, making it difficult for the power distribution system to operate normally. Therefore, when using thyristor-based online soft starters, a bypass contactor is still needed to supply the motor with full voltage. While adding a bypass contactor solves the power consumption problem, it still increases the overall size of the system. Therefore, the system cost is very high. Furthermore, the online operation of the thyristors introduces high-order harmonic pollution into the power grid, making harmonic mitigation of the grid more difficult. Figure 1. Thyristor-based online soft starter. 2.2 Bypass-type soft starter. Thyristor-based online soft starters present significant manufacturing challenges due to their high power consumption and heat generation, especially since the thyristor heatsink requires a large volume and mechanical ventilation. This leads to a substantial increase in technical difficulty and material costs. To avoid these heat dissipation and power consumption issues, the author developed a bypass-type soft starter in 1998, as shown in Figure 2. Figure 2. Bypass-type soft starter. Because the thyristor only operates briefly for a few seconds to tens of seconds during startup, its heat dissipation is minimal. Therefore, the soft starter body does not require a large heatsink, only about 1/10 the size of the online soft starter, making it several times smaller and eliminating the need for mechanical cooling. This approach is far superior to the previous one, resulting in a more rational engineering design. Therefore, bypass-type soft starters are now widely used in engineering applications. However, nothing is perfect. The disadvantages of bypass operation include the inability to integrate the starting device, complex circuitry, and the inability of a powerful intelligent soft-start controller to fully utilize its capabilities, leading to inconvenience in maintenance and repair. 2.3 Built-in Bypass Soft Starter A built-in bypass soft starter (referred to as a motor controller) is, as the name suggests, an internal contactor connected in parallel with the thyristor. During the soft start and soft stop of the motor, the thyristor operates, and the mechanical contacts open. When the motor is running normally, the thyristor closes, and the mechanical contacts close. This entire process is automatically completed by the internal controller; from the perspective of external wiring, it is a single device, hence the term "online operation." It can also be called a bypass soft starter, integrating the external contactor into the soft starter while maintaining a consistent size. Its advantages are that it possesses all the advantages of the above two types while avoiding their respective disadvantages: First, the circuit is simple; second, it is naturally air-cooled; third, the thyristor is only responsible for starting and stopping, avoiding the power consumption and heat dissipation caused by the online operation of the thyristor; fourth, the powerful intelligent controller can fully play its role, and can start, stop, protect and control the motor; fifth, it saves space; sixth, due to the integrated design of the thyristor and mechanical contact, the intelligent controller realizes that the mechanical contact is arc-free, so that the electrical life of the mechanical contact is equal to the mechanical life, solving the problem that contactors have long been difficult to solve, and greatly improving the reliability of the contactor compared with the bypass type soft starter, as shown in Figure 3. Figure 3 Built-in bypass type soft starter It retains the advantages of online operation soft starters and bypass operation soft starters, and avoids the disadvantages of the above two types. It is currently the internationally leading technology for soft starters. 2.4 Comparison of soft starter types The three types of soft starters currently popular on the market are: online type, bypass type and built-in bypass type. Online soft starters are mostly foreign brands, accounting for about a quarter of the market share. These are largely image-building projects and projects driven by ignorance. About half of the market uses bypass-type soft starters. Since the introduction of built-in bypass soft starters in 2003, their popularity has increased. Through the above introduction of the technological advantages of built-in bypass soft starters, readers should have a rational understanding. Below, we use data comparison for quantitative analysis, as shown in the attached table. The costs in the attached table refer to the manufacturers' publicly quoted prices; users' purchase prices are generally lower than these. The comparison of soft starter type parameters in the attached table shows that bypass-type soft starters are superior to online soft starters, and built-in bypass soft starters are superior to both bypass and online soft starters. However, the more advanced the technology, the lower the cost—a general rule of high technology. Comparing the brands listed in the appendix, online soft starters cost 1.5 times more than bypass soft starters, and bypass soft starters cost 1.4 times more than built-in bypass soft starters (excluding the contactor price). In terms of energy consumption, online soft starters consume approximately 10 times more energy than bypass soft starters, and bypass soft starters consume approximately 7 times more energy than built-in bypass soft starters. There are approximately 300 million kW of electric motors operating nationwide, and assuming 40% require soft starters, this equates to approximately 120 million kW of motors. In terms of investment, using online soft starters would require over 25.2 billion yuan, using bypass soft starters would require over 16 billion yuan, and using built-in bypass soft starters would require over 10 billion yuan. In terms of total energy consumption, using only online soft starters would result in an annual electricity consumption of 6.3 billion kWh, equivalent to the annual power generation of an 800,000 kW power plant. Using only bypass-type soft starters results in an annual power consumption of 630 million kWh, equivalent to the annual output of an 80,000 kW generator. Using only built-in bypass-type soft starters results in an annual power consumption of 80 million kWh, equivalent to the annual output of an 8,000 kW generator. Using only bypass-type soft starters saves 5.6 billion kWh of energy annually compared to using only online soft starters. Using only built-in bypass-type soft starters saves 550 million kWh of energy annually compared to using only bypass-type soft starters. 3. Conclusion Through the above analysis, it is clear that online soft starters should be replaced by bypass-type soft starters, and bypass-type soft starters should be replaced by built-in bypass-type soft starters. However, in practical engineering applications, some projects prioritize brand image or reliability, knowingly choosing inline soft starters when they deem it unreasonable. Since imported brands often lack bypass models, they reluctantly opt for imported inline soft starters. However, most of these choices stem from a lack of understanding of the intricacies. This article provides an analysis and explanation for reference. Currently, there are 5 or 6 manufacturers producing built-in bypass soft starters, catering to various user needs. Examples include: Tianjin Norhaden TJNR1 (15-400kW), ABB PST (200-560kW), AB Flex (15-250kW), Siemens 3RW44 (15-250kW), Danfoss (15-110kW), and Xi'an Xipu (15-75kW). Furthermore, all soft starter manufacturers are developing built-in bypass soft starters, and it is believed that before long, a situation will emerge where built-in bypass soft starters dominate the entire soft starter market. If users are still choosing bypass or online soft starters now, their spare parts and maintenance will be restricted in the near future.