What is a Power Capacitor?

Power capacitors are capacitors used in power systems and electrical equipment. Any two pieces of metal conductors are separated by an insulating medium to form a capacitor. The size of the capacitor is determined by its size and the characteristics of the insulating medium between the two plates.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

Quick Answer

A Capacitor is an electrical component, which is used to store electric charges temporarily. The unit of a capacitor is the farad (F). A Power Capacitor is a special type of capacitor, which can operate at higher voltages and has high capacitances.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

Power capacitor classification

Power capacitors can be divided into 8 types according to their purpose:mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

①Parallel capacitor. Originally called a phase-shifting capacitor. It is mainly used to compensate the reactive power of the inductive load of the power system to increase the power factor, improve the voltage quality, and reduce the line loss.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

②Series capacitor. It is connected in series in power frequency high voltage transmission and distribution lines to compensate the distributed inductance of the line, improve the static and dynamic stability of the system, improve the voltage quality of the line, extend the power transmission distance and increase the transmission capacity.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

③Coupling capacitor. Mainly used for high-frequency communication, measurement, control, protection of high-voltage power lines, and as components in devices for extracting electrical energy.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

④Circuit breaker capacitor. Formerly known as a voltage equalizing capacitor. Parallel connection on the fracture of the ultra-high voltage circuit breaker has the effect of equalizing the voltage, so that the voltage between the fractures is uniform during the breaking process, and can improve the arc extinguishing characteristics of the circuit breaker and increase the breaking capacity.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

⑤Electric heating capacitor. It is used in electric heating equipment systems with a frequency of 40 to 24000 Hz to increase the power factor and improve the voltage or frequency characteristics of the loop.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

⑥Pulse capacitor. It is mainly used for energy storage and is used as basic energy storage components such as impulse voltage generator, impulses current generator, and oscillating circuit for circuit breaker test.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

⑦DC and filter capacitors. Used in high-voltage direct current devices and high-voltage rectifier filter devices.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

⑧Standard capacitor. Used in the power frequency high voltage measurement dielectric loss circuit, as a standard capacitor, or as a capacitive voltage divider device for measuring high voltage.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

power capacitor.jpg

power capacitormCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

In the power system, it is divided into high-voltage power capacitors (above 6KV) and low-voltage power capacitors (400V)mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

Low-voltage power capacitors are classified into oil impregnated paper power capacitors and self-healing power capacitors according to their properties. According to the function, it is divided into ordinary power capacitors and intelligent power capacitors.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

Self-healing shunt capacitor.jpg

Self-healing shunt capacitormCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

Take American Swell products as an example to introduce smart power capacitors.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

Smart power capacitors integrate advanced technologies such as modern measurement and control, power electronics, network communications, automation control, and power capacitors. It has changed the backward controller technology of the traditional reactive power compensation device and the backward mechanical contactor or electromechanical integrated switch as the switching technology of switching capacitors. It also changed the bulky and bulky structure of the traditional reactive power compensation device, so that the new generation of low-voltage reactive power compensation equipment has better compensation effect, smaller size, lower power consumption, lower price, more flexible use, and more maintenance. The features of convenience and longer service life meet the higher requirements of modern power grids for reactive power compensation.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

Application fields

The main application areas are:mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

■ Factory Power Distribution SystemmCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

■ Residential district power distribution systemmCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

■ Municipal Commercial BuildingmCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

■ Traffic Tunnel Power Distribution SystemmCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

■ Box change, complete cabinet, outdoor distribution boxmCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

Cause of damage

In recent years, more and more power capacitors have been put into operation, but due to poor management and other technical reasons, power capacitors are often damaged and exploded. The reasons are as follows:mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

Breakdown of the internal components of the capacitor: mainly caused by the poor manufacturing process.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

The capacitor's insulation damage to the shell: The high-voltage side lead of the capacitor is made of thin copper. If the manufacturing process is poor, the edge is uneven, there are burrs or severely bent, and the tip is prone to corona. Corona will decompose the oil, expand the tank shell, and drop the oil level, causing breakdown. In addition, when the cover is sealed, if the welding time is too long at the corners, the internal insulation will be burned and oil and gas will be generated, which will greatly reduce the voltage and cause damage to the capacitor.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

Poor sealing and oil leakage: due to poor sealing of the assembly sleeve, moisture enters the interior, which reduces the insulation resistance; or the oil level drops due to oil leakage, resulting in pole-to-shell discharge or component breakdown.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

Bulging and internal dissociation: due to the internal corona, breakdown discharge and internal dissociation, the capacitor will reduce the initial dissociation voltage of the element to below the working electric field strength under the action of overvoltage, which causes physical, chemical, and electrical effects. Accelerate the aging and decomposition of the insulation, generate gas, form a vicious circle, increase the pressure of the box shell, and cause the outer wall of the box to bulge and cause an explosion.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

Capacitor explosion caused by charge closing: Any capacitor bank with a rated voltage is prohibited from closing with charge. Each time the capacitor bank is reclosed, the capacitor must be discharged for 3 minutes when the switch is disconnected. Otherwise, it may explode due to the residual charge on the capacitor at the moment of closing. For this reason, it is generally stipulated that capacitor banks with a capacity of more than 160 kvar should be equipped with automatic discharge devices when there is no voltage, and it is stipulated that the switches of the capacitor banks are not allowed to be equipped with automatic closing.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

In addition, the capacitor may be damaged and exploded due to excessive temperature, poor ventilation, excessive operating voltage, excessive harmonic components, or operating overvoltage.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

Precautions

1 When installing capacitors, the wiring of each capacitor should preferably be connected to the bus with a separate flexible wire. Do not use hard bus connections to prevent assembly stress from damaging the capacitor casing and breaking the seal and causing oil leakage.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

2 Any poor contact in the capacitor circuit may cause high-frequency oscillating arcs, which will increase the working electric field strength of the capacitor and generate heat. Therefore, it is necessary to maintain good contact between the electrical circuit and the grounding part during installation.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

3 When the capacitors of lower voltage levels are connected in series and run in the higher voltage level network, measures such as installing insulators equivalent to the operating voltage level should be adopted to ensure reliable insulation between the housing of each unit and the ground.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

4 After the capacitor is connected in a star shape, it is used for a higher rated voltage and the neutral point is not grounded. The shell of the capacitor should be insulated from the ground.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

5 Before the capacitor is installed, the capacitance should be allocated once to balance the phases, and the deviation should not exceed 5% of the total capacity. When a relay protection device is installed, it should also meet the requirement that the balance current error does not exceed the relay protection operating current during operation.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

6 The wiring of individual compensation capacitors should be done: for induction motors that are started directly or via a varistor, the power factor-increasing capacitor can be directly connected to the outlet terminal of the motor, and no switchgear or fuse should be installed between the two; For induction motors started with star-delta starters, it is best to use three single-phase capacitors, each capacitor is directly connected in parallel to the two terminals of each phase winding so that the connection of the capacitor is always consistent with the connection of the winding.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

7 For the grouping compensation low-voltage capacitor, it should be connected to the outside of the low-voltage grouping bus power switch to prevent self-excitation when the grouping bus switch is disconnected.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

8 The low-voltage capacitor bank for centralized compensation should be specially equipped with switches and installed on the outside of the main line switch, not on the low-voltage bus.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

Frequently Asked Questions

What are the 3 types of capacitor?
Three families are available, categorized according to their dielectric.

Aluminum electrolytic capacitors with aluminum oxide as dielectric.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

Tantalum electrolytic capacitors with tantalum pentoxide as dielectric.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

Niobium electrolytic capacitors with niobium pentoxide as dielectric.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

How long do power capacitors last?

Manufacturers of electrolytic capacitors specify the design lifetime at the maximum rated ambient temperature, usually 105°C. This design lifetime can vary from as little as 1,000 hours to 10,000 hours or more.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product

What causes power capacitors to fail?

Capacitors age over time, losing the ability to perform their job. The electrolyte, paper, and aluminium foil inside the capacitor degrades physically and chemically. Several factors, such as excessive heat or current, can speed up the deterioration rate.mCSElectronic Parts,Electronic Components distributor,memory,flash, integrated circuit,Original Product