EnviroVAr Sistema de Controle de Fator de Força

O EnviroVAr Sistema de correção de poder de força fornece eficiente compensação de forca reativa em toda area, industrial, comercial e Varejo de grande porte, onde se tem um custo execessivo com enérgia ou onde a corrente disponivel seja limitada e o custo de reposição de transformadores e suprimento de enérgia sejam proibitivos.  .

O Problema

A maioria de cargas elétricas trifásicas extraem não somente o poder ativo (quilowatt, a parte que faz o trabalho útil da fonte, mas igualmente reativa (poder do kVar, exceto o do Wattless’) os exemplos destas cargas seriam motores de indução, Ignição do motor (AC e DC), fontes de alimentação do interruptor-modalidade, e a maioria dos circuitos de ignição.

Para simplificar e mostrar um exemplo em um motor de indução, onde o poder ativo e extraido para que se faça o trabalho, enquanto o poder reativado o usado pela bobina do (stator) (parte fixa do motor) para criar o campo magnético. Campo magnético essencial para o funcionamento do motor, esse porém nao faz o trabalho, so permite que haja a transferencia de poder do stator para o rotor.

A demanda total de alimentação para uma carga desse tipo e chamada força aparente. É a soma dos vetores de ambos componentes: Ativo e reativo. O “fator de força” de uma carga e a proporção (razão) do poder ativo para o poder aparente, (kW-quilowatt para kVA Ampere Reativo) algumas vezes referente ao Cos (coseno) (f). Quando extrai-se uma carga de uma fonte alimentadora do poder reativo, e dito que fator de poder esta vagaroso e quando for transportada pela fonte dize-se que o fator de forca esta liderando. Essa e a referencia a fase da corrente da carga em respeito ao fornecedor de voltagem.

Essa e a “Disposição do Fator de Forca” ou DPF comumente conhecida como “Fator de Força” levando-se em consideração a frequencia dos componentes da voltagem e corrente.

When seeking to improve the power factor of a load, what is actually being done is to supply a proportion of the reactive power demand of this load locally. This results in a greater proportion of active current being drawn from the supply.

With a capacitor installed electrically adjacent to a load, the supply is required only to provide the active power demand, and a smaller proportion of the reactive power demand.

Physical Benefits of Power Factor Correction

The reduction in demand on the supply from the installation of Power Factor Correction equipment results in:

• ‘Spare’ supply capacity which may be used to connect additional load without the necessity of network reinforcement
• Reduced losses and hence reduced heating in transformers, cables and switchgear, increasing reliability, useful service life, and reducing servicing costs
• Reduction in reactive power demand from the supply improves voltage regulation, as to a first approximation, the voltage drop in a supply network is proportional to the reactive power supplied by that network ( D V @ QX, where D V is the voltage drop, Q the reactive power demand, and X the system reactance)
• An increase in Power Quality, as the presence of a large capacitor bank gives significant attenuation of mains borne voltage spikes, and can also reduce the effects of short duration dips or notches in the supply voltage
• Reduction in distribution system losses means that fewer kWh are required from the electricity generators, resulting in lower carbon dioxide emissions

Contractual benefits of Power Factor Correction

• Most contracts for the supply of electricity stipulate a minimum power factor for the load to be connected, though this is often ignored by both supplier and consumer until problems occur, at which point the solution is more costly than would have been the case had the situation been addressed initially
• Engineering Recommendation G5/4, (relates to planning levels for harmonic voltage distortion and the connection of non-linear equipment to transmission systems and distribution networks in the United Kingdom), is now enforceable legislation. The use of detuned capacitor banks has the effect of absorbing a proportion of any harmonic currents produced by the load, and can often result in compliance with G5/4 without the need for further harmonic reduction equipment.
• Engineering Recommendation P28, (relates to planning limits for voltage fluctuations caused by industrial, commercial and domestic equipment in the United Kingdom), details limits on ‘Voltage Flicker’. As the majority of flicker is caused by voltage drop due to sudden reactive power demand, the installation of power factor correction capacitors can reduce the levels of flicker to within acceptable limits without the need for supply reinforcement.
• Organizations having or seeking approval under ISO14001 (Environmental Management) can easily show increased electrical efficiencies and reduction in carbon emissions by implementing an appropriate Power Factor Correction scheme.

Financial Benefits of Power Factor Correction

• Reduction in kVA required to supply a given kW load means that initial capital expenditure can be reduced, as the primary distribution network components (transformers, switchgear etc.) can be reduced in rating and hence Cost.
• Reduction in losses in distribution equipment due to reduced demand on the supply is reflected in the kWh usage for the site. Whilst this reduction in kWh consumption may at first appear to be small, it can amount to between 1% and 3% of the total consumption, with the associated savings in electricity charges.
• The tariff under which charges are made for electricity may include items which relate directly or indirectly to poor power factor. These are usually specific to the consumer, and hence generalizations are difficult. Items falling into this category which may be affected include Authorized Supply Capacity, Metered Monthly Maximum Demand, and Reactive Unit charges.

EnviroVAr systems are available as both "standard" systems and also as "detuned" systems with additional inductive reactive filters to limit harmonic currents within a circuit. For a full understanding of these systems go to the links above and then contact your local EMS (European) representative to arrange a site survey to best advise you as to how you can benefit from effective power factor correction