What is a centrifugal switch?

In the field of electrical engineering and mechanical automation, centrifugal switch is an automatic control component that operates based on changes in rotational speed. It is widely used in various aspects such as motor starting protection and speed monitoring. This article aims to explore in depth the working principle, structural characteristics, and applications of centrifugal switches in different industries, and to provide prospects for future development trends.

Working principle and structure of centrifugal switch

The centrifugal switch is mainly composed of a housing, a spring, a counterweight (also known as a pendulum), a contact system, and other parts. When the equipment starts to operate, as the rotor speed increases, the counterweight installed on it is pushed away by the outward centrifugal force until it reaches the preset value, triggering the internal mechanism action to connect or disconnect the circuit. This design cleverly utilizes the characteristic in physics that "mass moving away from the center of rotation produces greater centripetal acceleration" to achieve non-contact control.

Core components:

• Shell: Provides overall support and protection.
• Spring: Used to maintain the position of the counterweight at low speeds.
• Weight block: Adjusting its own position according to changes in rotational speed is a key component for achieving switch function.
• Contact system: responsible for performing the final electrical circuit closure or disconnection operation.
• Working mode: divided into two basic types: normally open and normally closed. The former is in an open state in a stationary state and only closes when the speed exceeds a threshold; The latter, on the other hand, maintains a conductive state until the set speed is reached, and immediately cuts off the connection once overspeed occurs.

The main types of centrifugal switches

Normally open type:

• At low speeds, the circuit is disconnected.
• When the speed reaches the set value, the contacts close and the circuit conducts.

Normally closed type:

• At low speeds, the circuit is conductive.
• When the speed reaches the set value, the contacts open and the circuit disconnects.

Types of Motors That Do Not Contain a Centrifugal Switch

The most common types of motors that do not contain a centrifugal switch are: capacitor start capacitor run split phase motors and permanent split capacitor (PSC) motors.

Capacitor Start Capacitor Run Split Phase Motor

The capacitor start capacitor run split phase motor is a motor that uses a combination of capacitors to control the speed of the motor. The motor is designed to start with a high initial torque, which is achieved by using a start capacitor. Once the motor is running, the run capacitor is used to maintain a steady speed. This type of motor is often used in applications such as fans, blowers, and pumps.

Capacitor Start and Run Motor, Capacitor Start Induction Motor, Non-Centrifugal Motor
One of the main advantages of the capacitor start capacitor run split phase motor is that it is relatively inexpensive to manufacture and maintain. Additionally, this type of motor is relatively simple to control, making it a popular choice for many applications. However, one of the main disadvantages of this motor is that it is not as efficient as other types of motors, which can result in higher energy costs over time.

Permanent Split Capacitor (PSC) Motor

The permanent split capacitor (PSC) motor is another type of motor that does not contain a centrifugal switch. This type of motor uses a single capacitor to control the speed of the motor. The capacitor is permanently connected to the motor, allowing for a steady, consistent speed. PSC motors are commonly used in applications such as fans, blowers, and pumps.

Permanent Split Capacitor Run Motor, Permanent Split Motor, Capacitor Motor, Non-Centrifugal Induction Motor, Single Phase Motor
One of the main advantages of PSC motors is that they are relatively simple to control, making them a popular choice for many applications. In addition, this type of motor is relatively inexpensive to manufacture and maintain. However, one of the main disadvantages of PSC motors is that they are not as efficient as other types of motors, which can cause energy costs to increase over time.

Application scenarios of centrifugal switches

Centrifugal switches play an important role in many fields due to their unique working mechanism:

• Motor starting control: Especially suitable for auxiliary winding switching of single-phase asynchronous motors, it determines whether to remove the auxiliary circuit from the main circuit by detecting the speed increase after the starting phase ends, in order to improve efficiency and prevent overload damage.
• Safety protection devices: such as washing machine dehydrator overspeed protection, industrial fan speed limit, etc., can effectively avoid safety hazards caused by abnormal high-speed operation.
• Vehicle engine management system: Some older models may use such sensors to monitor the actual output power of the engine, ensuring that it is within the optimal operating range.
• It can also be found in household appliances and other consumer electronics products, such as vacuum cleaners, mixers, and other small household appliances, to optimize performance and extend service life.

Technological progress and development prospects of centrifugal switches

In recent years, with the advancement of materials science and the continuous improvement of manufacturing technology, centrifugal switches are developing towards smaller volume and higher precision. The application of new materials makes products lighter and more durable; Precision machining technology helps reduce assembly errors, improve response speed and accuracy. In addition, the trend of intelligence has also brought new opportunities to this field - intelligent centrifugal switches integrated with microprocessors can achieve more complex functions, such as fault diagnosis, remote monitoring, etc., further expanding their application scope.

Summary

In short, as a classic and constantly evolving mechatronics component, centrifugal switches play an indispensable role in modern society due to their simple and reliable characteristics. Both traditional manufacturing and emerging technology industries cannot do without this small but crucial 'guardian'. Faced with the ever-changing technological changes, we have reason to believe that centrifugal switches in the future will become more intelligent, flexible, and better serve every corner of human life.

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FAQs

What is a centrifugal switch? What does it do?

• A centrifugal switch is a mechanical switch based on centrifugal force, commonly used in single-phase motors. It automatically switches the starting and running windings by sensing the motor speed so that the motor can run stably.

How does a centrifugal switch work?

• A centrifugal switch uses centrifugal force to sense changes in the motor's speed. When the motor speed reaches a certain value, the centrifugal switch opens, cuts off the starting winding circuit, and allows the motor to work only on the running winding, reducing power consumption and heat generation.

In which devices are centrifugal switches usually used?

• Centrifugal switches are often used in single-phase motors, such as washing machines, air conditioning compressors, water pumps and other motor equipment to ensure automatic switching between starting and running states.

How to determine if a centrifugal switch is damaged?

• Symptoms of centrifugal switch failure include the motor failing to start, abnormally large starting current, or a buzzing sound from the motor. This may be a sign of poor switch contact or a damaged switch.

How does a centrifugal switch affect the starting and running of a motor?

• The centrifugal switch controls the on and off of the starting winding. If the switch fails to cut off the starting winding normally, the motor may overheat or fail to accelerate normally, affecting the life of the motor.

What are the common causes of centrifugal switch failure?

• Common causes of failure include contact wear, switch spring fatigue, delayed switching due to insufficient centrifugal force, and poor contact due to dust or debris.

How to clean and maintain a centrifugal switch?

• Regularly remove dust and oil from the centrifugal switch, check the contact points for burn-in, and ensure that the switch spring is in good condition to extend its service life.

Can a centrifugal switch be removed during motor modification or repair?

• It is generally not recommended to remove a centrifugal switch. Without a centrifugal switch, the starting winding may continue to work, causing the motor to overheat or even damage, unless an electronic starting device is used instead.

What is the difference between a centrifugal switch and a thermal protector?

• A centrifugal switch switches the starting winding according to the speed and is a mechanical control; a thermal protector is a temperature sensing device that automatically disconnects the circuit when the motor temperature is too high to prevent overheating.

Is there an electronic device that replaces the function of a centrifugal switch?

• Yes, an electronic starting relay or solid-state controller can replace a centrifugal switch, which has higher reliability and response speed and is suitable for use in motors that require high stability.