What is a Capacitor Controller? Functions and instructions for use

BTB Electric

• News
• Apr 23, 2025
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Capacitor controllers are an important component of the power system, in the context that every power system is facing the problem of optimizing costs and operational efficiency. This device calibrates the power factor and minimizes energy consumption costs. Join BTB Electric to learn in detail the functions, technical characteristics, operating principles and notes when using the compensating capacitor controller in the following summary.

What is a Capacitor Controller?

A compensating capacitor controller or power factor relay (Power factor relay) is a device that controls the power factor in the electrical system. The power factor represents the quality of power and the cost of electricity use. The value of the power factor cosφ is approximately 1 indicates a quality power system, further down to 0 indicates that there has been a power loss. The low cosφ coefficient causes an increase in electrical energy consumption and an increase in periodic operating costs.

The compensating capacitor controller ensures that the power factor is controlled within the optimal allowable threshold, minimizing energy loss. This is a central unit located in a compensating capacitor cabinet with a reactive power compensation function. With intelligent automatic features and high-precision control, the automatic compensation method using this device is gradually being replaced by manual and passive compensation systems.

Currently, there are a variety of capacitor controller manufacturers on the market, in which products from BTB Electric are widely used in many fields from industry, distribution systems to commerce.

Working Principle of Capacitor Controller

The compensating capacitor controller relies on real-time monitoring of the power factor in the electrical system. When the power factor drops below the warning threshold, the controller sends a control signal to the compensator to generate the useful power needed to increase the power factor.

The working principle of the compensating capacitor controller goes through the following steps:

• Power Factor Monitoring: Continuously check the power factor value of the system using input voltage and current.
• Decision Making: Automatically determines the number of compensating capacitors to turn on when the power factor drops below the initial set value.
• Compensating capacitor control: Controls the correct number of compensating capacitors on and off so that the cosφ power factor is always at the optimal level.

The measurement-decision-making process – control is continuous and at the same time the power factor relay will continuously change the capacitors that operate alternately.

Functions of the compensating capacitor controller

The capacitor controller has up to 5 main functions to improve system quality:

• Automatic Capacitor Control: Controls the on/off of 1 or more capacitors to achieve the required power factor.
• Increase energy efficiency: Maintain a stable power factor threshold of the system, reduce energy usage, and reduce electricity costs.
• Reduced reactive power: Reactive power increases the power consumption of the system.
• Prevention of penalties from electricity: Automatic adjustment of power factor, maintaining the ideal range of power factor, avoiding arising electricity charges.
• Improving system stability: Continuous control of the power factor, maintaining stable operation for devices.

Types of Capacitor Controllers

The capacitor controller is divided by number of levels with 4, 6, 8, 12, 16, 24 or 32 levels. Based on the system characteristics and the number of compensators to select the number of control levels:

• Type 4 is used for small power systems.
• Type 6 is used for medium power systems.
• 8-level, 12-level, 16-level types are used for large-capacity power systems.
• The 24-level and 32-level types are used for very large-capacity power systems, and the compensation method is complicated.

BTB Electric has 6-level, 8-level, 12-level, and 32-level capacitor controller lines.

Capacitor controllers measure a variety of parameters such as voltage, current, power factor, power range, total harmonic distortion, temperature,... to generate appropriate warning signals and control capacitors. There is also a type of intelligent capacitor controller used for high-capacity, highly automated industrial electrical cabinets.

Specification of Compensating Capacitor Controller

BTB Electric Capacitor Controller consists of 3 series: Standard, Special and Smart. The technical characteristics of this 3 series capacitor controller are as follows:

Notes when installing and using the compensating capacitor controller

Before installing the compensating capacitor controller, you need to carefully study the device parameters and read the user manual carefully or get assistance from a professional. BTB Electric Capacitor Controller products have detailed installation and usage instructions.

Basic installation steps for the compensating capacitor controller:

• Select the installation location in the electrical cabinet, ensuring dryness, ventilation, vibration limiting, and ideal ambient temperature.
• Connect the power cord and signal wire in and out to the controller.
• Perform the steps to set the operating mode, adjust the C/k, adjust the cosφ, select the number of steps, adjust the step-time, select the switching equation,...
• Double-check connections and settings before powering off.

Configuration steps are performed at the remote control screen or software. In addition to complying with the user manual and technical requirements, it is necessary to comply with safety regulations when operating the compensating capacitor controller.