I. Definitions and Functions

Bypass: Bypass reduces the impact on a component or part of a circuit by introducing a branch in the circuit that allows the current to bypass that component. It is often used to reduce electromagnetic interference, eliminate circuit noise, or filter treatments.
ON-LINE SOFT STARTER: An on-line soft starter is used to control the motor starting process by gradually accelerating the motor speed and limiting the starting current and torque. It is mainly used to gradually increase the voltage and frequency of the motor by means of soft start during high-current starting, so as to achieve a smooth transition of the starting process.
Frequency converter: Frequency converter is an electronic device used to control the frequency regulation of AC motor. It achieves motor speed regulation and control by changing the input voltage and frequency of the motor. Frequency converter can achieve precise speed control of motor to meet different working requirements.

II. Working Principle

Bypass: Bypass bypasses specific components by adding bypass branches to reduce the current impact and interference to them. It mainly relies on components such as diodes, inductors, capacitors and filters.
In-line soft starter: In-line soft starter first converts AC to DC and supplies power to the motor through a capacitor. It achieves smooth starting by controlling the magnetic flux and gradually accelerating the motor speed.
Inverter: An inverter converts AC to DC through a rectifier and stores it in a capacitor. The filter then purifies the DC and the inverter converts it to AC with adjustable frequency and voltage. The control system adjusts the output according to the motor status, user input and internal parameters to achieve precise control.

III. Application Scenarios

Bypass: Bypass is suitable for circuits that need to reduce electromagnetic interference, eliminate circuit noise or perform filtering processing. It is often used in applications with high requirements for electromagnetic compatibility.
On-line soft starter: On-line soft starter is suitable for electric motors that need smooth starting and protection, such as compressors, pumps, fans, conveyors and crushers. These devices need to limit the starting current and torque during startup to avoid shock to the grid and equipment.
Frequency converter: Frequency converters are widely used in the lift industry, industrial production, air-conditioning systems and wind power generation. By adjusting the running speed of the equipment, frequency converter can realise the automatic control of the production process, save energy and improve the production efficiency. At the same time, frequency converter can also realise soft start and soft stop of motor, reduce equipment wear and prolong service life.

Fourth, the selection guide

When selecting a motor control solution, the following factors need to be considered:Motor type: different motor types have different requirements for control solutions. For example, AC motors usually require speed control using an inverter, while DC motors may require other types of controllers.
Starting requirements: For equipment that needs to limit starting current and torque, an in-line soft starter may be an option. If only simple circuit protection or filtering is required, bypass may be a more economical option.
Speed Regulation Requirements: If precise control of the motor’s operating speed is required, a frequency converter is the best choice. It can adjust the motor’s speed and load capacity according to actual needs.
Cost and Maintenance: Different control solutions differ in terms of cost and maintenance. When choosing, you need to comprehensively consider the initial investment in equipment, operating costs and maintenance costs and other factors.
In summary, bypass, online soft starters and inverters each have their unique roles and application scenarios in motor control systems. When choosing the appropriate control scheme, comprehensive consideration needs to be made according to the specific needs and working environment.