Nokian Capacitor's low voltage power capacitors are manufactured by using the latest methods. Capacitor elements of metallized polypropylene film are self-healing and dry without impregnation liquid. Each capacitor element is individually protected with patented internal protection.

 
Capacitors have low losses, and are constructed to be compact size and light in weight. The low voltage power capacitors comply with most national and international standards.
Automatic capacitor banks with blocking reactors are intended for power factor correction in systems where harmonic distortion is present. Each step of the bank consists of a capacitor unit with a blocking reactor. These form a series resonant circuit tuned to a frequency below that of the lowest harmonic, normally the 5th. The step is designed to be capacitive fundamental frequency (50 / 60 Hz ), and it thus provides power factor correction at this frequency. At harmonic frequencies the blocking reactor is dominant and the step is therefore inductive.
There is no amplification of the harmonics, because there is no parallel resonant circuit between the blocking reactor bank and the network. The bank also acts as a detuned filter removing a certain amount (15…50%) of lower harmonic currents from the network.

As in conventional automatic capacitor banks, the stages are controlled by a reactive power regulator. Automatic capacitor banks with blocking reactors are manufactured for different network voltage and frequency ratings.
Low Voltage Equipment

Power transmission and distribution systems are designed to operate with sinusoidal voltage and current waveforms at a constant frequency. However, when nonlinear loads are connected to the system, excessive harmonic currents are generated, and this causes both current and voltage distortion. Nonlinear one-phase loads such as fluorescent illuminators and computers which are connected between phase and neutral, are generating third harmonic and multiple of it. All harmonic currents cause both current and voltage distortion. In addition to this third harmonic currents accumulate in the neutral wire increasing the risk of overloading and causes magnetic field harmonic from the network the above mentioned problems can be eliminated.

The best result can be reached, when the filter is connected as close as possible to the harmonic source. This is the best way to minimize harmonic current and voltage distortion.

In case 3rd harmonic voltage distortion and/or overloading current are major problems it is recommended to install the filter in the main switchboards.

Low Voltage Equipment

Harmonic filters consist of capacitors connected in series with a reactor. The capacitors produce reactive power at the filter's fundamental frequency, and the circuit is designed to achieve the required power factor correction. The inductance of the reactor is chosen so that the filter forms a very low impedance series resonant circuit at the harmonic frequency. This ensures that a high proportion of the harmonics enter the filter.

A typical harmonic filter consist of three series resonant circuits tuned to the most common harmonics (5th, 7th and 11th harmonic). The filters are housed in steel cubicles. Each consists of a contactor, thermal over-current relay, reactor and capacitors, the unit is generally connected to the fused feeders on the main distribution boards.

Harmonics filters can be operated in the same way as automatic capacitor banks: they are controlled by means of reactive power controller according to reactive power requirements.

Harmonics filters are custom designed for each application using standard components. This ensures that the best possible power factor correction and filtering characteristics are achieved for a reasonable investment.
Low Voltage Equipment

The thyristor switched capacitor banks are designed to support the line voltage during heavy intermittent loads. The voltage drop at the point of common coupling (PCC) is decreased to a level accepted by the power utility, when the power factor is improved. Suitable applications are e.g.

  • High power welding equipment

  • Steel rolling mill


    • As the capacitive compensation is switched on and off using thyristor switches, instead of contactors, a fast response is achieved without any mechanical wear, noise or excessive transients associated with contactor switching. The reactive power of the load is measured and the compensative capacitive power steps are normally equal in size.