Contactors for Power Factor Correction New capacitors place additional demands on contactors to keep power circuits balanced. Ind. Control Div., Eaton Corp. • Electrical power sources supply two types of power to inductive loads: real power in kW and reactive power in VAR. • Power-factor correction circuits can be either an individual style or of the bank/group style. • Banked or group PFCs are typically controlled with a VAR controller Most loads applied to modern electrical-distribution systems are inductive. Electric motors, transformers, and high-intensity discharge lighting make up a large portion of the power consumed in an industrial setting and all contribute to the inductive load. An inherent problem with inductive loads is that they lead to poor PFs that degrade overall system-operating efficiency. When applied correctly, power-factor-correction (PFC) systems can eliminate the negative effects of a poor PF. Readers will probably recall that inductive loads need two types of power: Working or real power, measured in kilowatts (kW), performs the actual work of creating heat, light, motion, and so forth. But inductive loads also need a second type of power known as reactive power, measured in kilovolt-Amps reactive (kVAR), to sustain the magnetic field inherent to inductive loads. When combined, working and reactive power form apparent power measured in kilovolt-Amps (kVA): the total power supplied to the system by the power source. The power factor (PF) of a circuit is the measure of electrical distribution efficiency. In simple terms, it is the ratio between the amount of real power used to perform actual work (kW) and the apparent power (kVA) supplied by the power source. For example, if the apparent power of a circuit was 200 kVA, but only 190 kW of actual work is done, then the PF is said to be 0.95 or 95%. Low PFs can lead
Products & Services
KVA meters measure the apparent power of AC devices in kilovolt-amperes (KVA). Apparent power is the combination of a circuit’s true power and reactive power.
Power meters are used for high-accuracy measurements of power over a wide-frequency bandwidth, and from both AC and DC circuits.
Power Quality Analyzers and Monitors
Power quality analyzers measure and monitor electrical power parameters to avoid disturbances, track steady-state variations, and ensure the reliability of power distribution systems.
Electrical contactors are used to switch high power in power circuits. Unlike relays, these electrical devices are normally connected directly to the load or current-carrying circuit.
Topics of Interest
Power Factor (pf) is the ratio of real power to total power. Real, or productive power, is the actual power used in a building, measured in kilowatts (kW). Reactive power generates the magnetic field...
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Lawrence J.Hollander, P.E.
Dean of Engineering Emeritus
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