The Fundamental Differences between Capacitor Contactor and Regular Contactors

In industrial electrical systems, contactors are widely used for controlling and starting electrical devices. In this field, capacitor contactors stand out as a special type of contactor with unique characteristics. This article aims to introduce and analyze three fundamental differences between capacitor contactors and regular contactors. Understanding these differences allows for grasping the needs, advantages, and disadvantages of each, enabling appropriate choices for specific applications.

The first fundamental difference between capacitor contactors and regular contactors lies in their capability to control and manage capacitor power. Due to this capability, capacitor contactors are particularly used in applications requiring capacitor control to enhance system performance and efficiency. In contrast, regular contactors are generally utilized for controlling resistive loads or loads that do not require capacitor power control.

Capacitor contactors are a type of contactor employed for controlling and managing capacitor power in electrical systems. Capacitors, as electronic components, store electrical power and discharge it to the system when needed. However, the use of capacitors may come with challenges such as high current, temperature rise, and voltage fluctuations.

Capacitor contactors are employed to control and manage these challenges. They can control and interrupt capacitor current and benefit from improved capacitor performance. These contactors typically consist of disconnectors, terminals, and control units that synchronize the control of capacitor operation.

Capacitor contactors utilize advanced electronic technologies and special components like capacitor controllers. These controllers can precisely control capacitor current and automatically adjust capacitor operation. This capability enhances system performance and reduces capacitor-related issues.

The applications of capacitor contactors include industries, power plants, electrical distribution systems, and power generation and transmission systems.

Advantages of Capacitor Contactors over Regular Contactors

One of the most significant advantages of using capacitor contactors is their high lifespan. When choosing capacitor contactors, it’s important to note that their price is generally higher compared to regular contactors.

Furthermore, regarding capacitor contactors, it can be noted that they experience fewer losses during their connection. Generally, regular contactors deteriorate quickly and require lengthy repairs. However, capacitor contactors require less maintenance and repair, resulting in fewer work interruptions.

These advantages have led to capacitor contactors being highly favored for use in capacitor bank electrical panels.

Differences between Capacitor Contactors and Regular Contactors

One of the essential equipment used in capacitor bank electrical panels is capacitor contactors. These contactors fundamentally differ from regular contactors. When a capacitor contactor is connected to the grid, it faces high electric currents due to the presence of capacitor electrons. Therefore, when a circuit is connected to a capacitor, the capacitors in the circuit are automatically discharged into their new capacitor.

By utilizing contactors, the issues with capacitors are improved. These contactors have high resistance and simultaneously protect capacitors from hazards. They feature series-wound wires and air-core, enhancing capacitor performance.

How do Capacitor Contactors Function in Capacitor Bank Panels?

Capacitor contactors installed on capacitor bank panels offer numerous advantages and functionalities. In these types of panels, auxiliary contacts are connected to the main contactors. These contacts are linked to the main contacts via resistive wires and assist in the initial charging of capacitors, thereby safeguarding the contactor from potential damages.

Once the main contacts are closed, the auxiliary contacts are disconnected from the circuit, and capacitors are powered by the stored contactors. Replacing auxiliary contacts is simpler and less costly compared to main contactors.

These contactors are specifically designed for connection to capacitors, hence the term “capacitor contactors.”

Why is the Selection of Capacitor Contactors Important?

The significance lies in the fact that surge currents can not only damage capacitors but also cause harm to the network and lead to the burning of contactor paths and fast-acting fuses. Therefore, the use of capacitor contactors for a capacitor bank that is frequently switched on and off is inevitable and essential. Now, we can examine the precise structure of these contactors, elucidating how they mitigate this initial surge current.

As you may know, over time, a capacitor becomes a fixed resistance and resolves the issue of the initial surge current. Thus, if there is a resistance in the capacitor path for a few seconds initially, and then it is removed from the path after this short period, the mentioned issues will be resolved. Capacitor contactors precisely perform this function, as depicted in the accompanying images.

How to Choose the Right Capacitor Contactor?

For selecting contactors, catalogs provided by manufacturers specify three currents, each accompanied by the corresponding amperage. It’s important that the amperage specified for AC1 current is significantly lower than AC3, as AC3 loads exhibit inductive states and initial surge currents. If AC6b is not listed, the AC6b current value must be calculated for use in capacitor banks.

The capacitor step current is equivalent to the rated current of the capacitor contactor AC6b and its ratio to the capacitor step power in kilowatts per line voltage in kilovolts is threefold.

You can purchase the contactor through ElectroShield and contact our specialists. For selecting a capacitor contactor, AC6b type must be used, capable of disconnecting and connecting the load with capacitor properties. The required current is calculated for the contactor according to the above formula.

Selection Table for Capacitor Contactors

How should we go about selecting a capacitor contactor? Which contactor is suitable for each step of the capacitor bank? Is there any difference between a capacitor contactor and a regular contactor?

To answer these questions, we must first familiarize ourselves with the concepts of resistive and inductive loads. Essentially, a contactor is an electrical device that performs the function of connection and disconnection using a magnetic mechanism and actuation of its tongues. The mode in which we want to switch the load on and off is crucial. The international standard IEC defines various types of loads for us, providing specific definitions for each. Here, for selecting an appropriate contactor for switching capacitor steps, we delve into the definition of three types of loads:

1. Loads indicated by the term AC1 are purely resistive loads that do not contain inductive or capacitive currents. Examples include contactors used solely for turning on a heater and similar applications.

2. Loads indicated by the term AC3 are motor loads, as motors inherently have inductive and coil-like properties.

3. Loads indicated by the term AC6b are solely capacitive loads.

Capacitive loads are of utmost importance due to their extremely high surge currents and the long duration of this current. Additionally, capacitors store electrical energy as voltage, requiring appropriate precautions for their connection and disconnection.

In the relevant catalogs provided by manufacturers, these three currents are displayed along with the corresponding amperage for each. It is evident that the amperage specified for the AC1 current is significantly lower than AC3, as AC3 loads have inductive states and initial surge currents. Essentially, if AC6b is not listed, we must specify this contactor for use in the capacitor bank.

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