What is the difference between lagging power factor and leading power factor?
Power factor is the ratio of watts (true power) to VA (volt-amperes, also called apparent power). Where the load is resistive only, the power factor is one, or unity, because the voltage waveform and the current waveform are in phase. Thus, for resistive loads only, true power and VA are the same. Where the load is reactive, the load stores energy, releasing it during a different part of the cycle. This shifts the current waveform so that it is offset, or out of phase with the voltage waveform. Reactive loads can be inductive (electric motors), capacitive, or non-linear (rectifier power supplies). When the load is inductive, the inductance tends to oppose the flow of current, storing energy then releasing it later in the cycle. The current waveform lags behind the voltage waveform. When the load is capacitive, the opposite occurs, and the current waveform leads the voltage waveform. So, lagging vs. leading is another way of saying the net reactance is either inductive or capacitive. This is slightly simplistic, and what we are talking about above is really DPF, or Displacement Power Factor. Non-linear loads don't really shift the current waveform, they distort it. The current waveform starts to look like a square wave, and square waves contain harmonics. So non-linear loads add harmonic distortion, and this tends to mimic a capacitively reactive load, adding some leading power factor. So when we say power factor, we really must include DPF plus harmonic distortion in total. One memory aid that may help to remember all this is: ELI the ICE man The L in ELI means inductance. The E (voltage) comes first, then the I (current) lags behind. Inductive reactance produces a lagging power factor. The C in ICE means capacitance. The I (current) comes first (leads) then the E (voltage) comes later. Capacitive reactance produces a leading power factor. Remember, it's always the current waveform that is affected by the reactive load, so you have to think about whether the current is leading or lagging. Most reactive loads are inductive, so at most sites the PF is lagging. One cool tidbit is that capacitive reactance cancels out inductive reactance. So if we have a building full of motors, we can add a bunch of capacitors to improve our power factor, meaning we get as close to unity as we can. Thus we have power factor correction capacitors that are made just for this purpose.
18 people found this useful
When there is an inductive element in the circuit, the current lags behind the voltage. an ideal inductor will make the current lag behind the voltage by 90 degrees.. a capac…itive element on the other hand will make the current lead the voltage (ideally by 90deg). That's why capacitors in parallel with the system are used a lot for power factor correction
Lead. Definitely, without a doubt.
underdamped Answer A lagging power factor describes a situation in which the load current is lagging the supply voltage. This describes an inductive load, such as a motor,… etc.
Actually, it can lead or lag. Power factor is said to be leading if the load is capacitive, and lagging if the load is inductive. Since most reactive loads (like motors) are… inductive, the power factor in most buildings is lagging. Additional Information ... The term 'leading' or 'lagging' with regard to power factor is determined by the current waveform relative to the voltage waveform. If the current leads the voltage, then the load has a leading power factor; if it lags the voltage, then it has a lagging power factor.
Any time the power factor is less than 1, whether it is leading or lagging, the efficiency is less than optimal. As power factor declines, more power is required to do the sam…e amount of work. Leading or lagging simply refers to the load being more capacitive or inductive. The disadvantage of a lagging power factor is that the load is highly inductive. Where power factor declines, greater losses are registered in the generation/distribution/transmission areas. Comment Power factor has nothing to do with efficiency. As power factor reduces, the true power of the circuit is unaffected, while the apparent power increases. The operation of load devices, such as motors, are completely unaffected.
A lagging power factor is caused by inductive reactance, which is composed of resistance and inductance -- and the resistance component lowers the supply volts. A leading powe…r factor provides capacitive reactance that actually helps improve source voltage -- this helps motor loads run cooler..
Power factor measures the phase difference between voltage and current. If they are in phase the Power Factor is one. If the current and voltage are out of phase the power fac…tor is between zero and one. You can describe the PF by saying the current lags the voltage with a PF = .8 or the voltage leads the current with a .8 PF.
when lagging Power Factor changes to leading PF, then the voltage across the circuit in which capacitor bank is connected, is increased.
Power factor is the cosine of an AC circuit's phase angle, where the expression phase angle is the angle by which a load current lags or leads the supply voltage. Lagging ph…ase angles and power factors occur in resistive-inductive circuits. Leading phase angles and power factors occur in resistive-capacitive circuits. Most industrial and commercial loads are combinations of heating (resistive) loads and motor (inductive) loads -in other words, resistive-inductive loads. Accordingly, lagging power factors tend to be more common than leading power factors.
As a power factor value can only vary between 0 and 1, presumably you mean 0.8, rather than '08'? The terms 'leading' and 'lagging' refer to whether the load current is lead…ing or lagging the supply voltage in an a.c. circuit. A leading current results from a capacitive load, whereas a lagging current results from an inductive load. So, a 'leading power factor' indicates a capacitive load, whereas a 'lagging power factor' indicates an inductive load. A figure of 0.8 (in fact, any figure other than 0 or 1) indicates that the circuit is a combination of resistance and reactance. To summarise, '0.8 leading' is an example of the power factor of a resistive-capacitive load, and '0.8 leading' is an example of the power factor of a resistive-inductive load.
As the name implies, motors are resistive-inductive loads, which means that their load current must lag the supply voltage. By definition, a lagging power factor is the co…sine of the angle by which the load current lags the supply voltage .
By connecting a capacitor (or capacitors), of appropriate reactive volt ampere rating, in parallel with the load.
In Electronics Engineering
By definition, the terms 'leading' and 'lagging' refer to what the load current is doing with respect to the supply voltage. So, for a 'lagging power factor', it is the curre…nt that is lagging.
In Electrical Engineering
A 'leading' power factor is one in which the load current leads the supply voltage, whereas a 'lagging' power factor is one in which the load current lags the supply voltage. …So resistive-capacitive circuits are 'leading', whereas resistive-inductive circuits are' lagging'.
In Electrical Engineering
A lagging power factor means that the current is lagging behind thevoltage. That means that in the AC cycle (50 or 60 Hz) the currentreaches its peak after the voltage. The am…ount of lag can be up to90 degrees which means one quarter cycle, or 5 milliseconds in a 50Hz system.
In Electrical Engineering
The coil consists of inductance. Due to inductance the current lags the voltage. So, the power factor is lagging.
In Electrical Engineering
With a lagging power factor the phase of the current lags thevoltage, as happens in an inductive load. With a leading powerfactor the current phase leads the voltage, as happe…ns in acapacitor. A lagging power factor is usually the problem in electricitysupply. A load such as a motor with a lagging power factor can haveits power factor corrected by placing a capacitor in parallel. TheVA rating of the capacitor should be equal to the VAR (volt-ampsreactive) taken by the load.