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Answered 2012-06-19 10:29:21

power factor correction

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What is the effect on the supply current if the capacitor is removed?

It depends on how the capacitor is connected and whether the supply voltage is a.c. or d.c. Assuming you are talking about a power-factor improvement capacitor (connected in parallel with an inductive load, supplied with a.c.), then the supply current will reduce.

Why capacitor is always connected to DC supply?

is it ? are you sure ? but i know so many circuit where capacitor is connected with ac supply . still , if u connected a capacitor to dc supply , then : 1. if it is in SERIES with the dc supply , it will block all the dc current as capacitor provides infinite resistance to dc current . application : where u want to block dc current.(simple high pass filter) 2. if it is in PARALLEL with the dc supply , it will not block dc current , but if any ac current comes out from the supply , the ac current will go through the capacitor , as capacitor provides small resistance to ac current. application : a) where u want to block ac current.(simple low pass filter) b) to filter the noise (ac components) of dc supply.

What is a capacitor bank and why is it used?

A Capacitor Bank is a group of several capacitors of the same rating that are connected in series or parallel with each other to store electrical energy . The resulting bank is then used to counteract or correct a power factor lag or phase shift in an alternative current (AC) power supply. They can also be used in a direct current (DC) power supply to increase the ripple current capacity of the power supply or to increase the overall amount of stored energy. There are some specific advantages of using capacitor bank such as, a) It reduces line current of the system. b) It improves voltage level of the load. c) It also reduces system Losses. d) It improves power factor of the source current. e) It reduces load of the alternator. f) It reduces capital investment per mega watt of the Load.

What capacitors draws more current?

Well firstly, is the capacitor connected to a DC or AC supply. On a DC supply the capacitor would draw current until it had fully charged, at which point the current falls to the leakage current. Electrolytic capacitor will always leak a little. On an AC connection, current will pass continuously, and the capacitor may rupture if connected across an AC supply. The current that would flow on an AC connection is given by the impedance, which is calculated from the reciprocal of 2 x Pi x F x C Because it is the reciprocal, the impedance reduces as the capacitance in Farads (F) increases. So, the bigger the capacitance, the higher the current. Therefore, for AC, only low values of capacitor are found connected across the supply (usually with a resistor in series) for interference snubbing across a contact or switch. Larger values are placed in series with the current, to act as current limiters or high pass filters.

Explain the function of the capacitor and inductor in a power supply?

A capacitor resists a change in voltage (dv/dt = i/c). An inductor resists a change in current (dl/dt = vl). Together, a capacitor and inductor make a tuned circuit. Usually, in a linear power supply, there is a capacitor in parallel with an inductor in series, and often, in a pi filter, another capacitor in parallel. This reduces the peak to peak voltage at the output. It is also possible to put an inductor in series with the rectifier diode, as as to reduce inrush current. In a switching power supply, things are a little bit different. The primary inductor is a current pump, maintaining constant current flow to the load, controlled by the pulse-width oscillator which switches between on-current from source and off-current from schottky diode. The capacitor in this case filters the output, so as to reduce high frequency harmonics.

What effect a capacitor has on a supply current on an inductive load?

it will improve the power factor... The angle between voltage and current will decrease depends on capacitor value.

Why you use capacitor as a filter in power supply?

capacitor acts as a small battery ,during rectification ac to dc it gets some blank space (no current) to fill this current from capacitor is used.

What does a power supply capacitor hold?

when the current supply to the capcitor it can store or hold little amount of charge

Why Capacitor blocks dc and allows ac explain therotically?


Can a capacitor be charged with an ac supply?

No. A capacitor can only be charged with a DC supply, or with an AC supply rectified with a diode, essentially making it a DC supply. If you put AC across a capacitor it will act like a short circuit. Capacitors pass AC current through them. Each half of the alternating current will charge and then discharge the plates, causing an AC flow through it.

What happens when a capacitor is connected to a dc supply?

Dc current cannot pass through a Capacitor as it get charged only if alternating pulses(sine wave) are applied as the input.As a result,the capacitor cannot get charged. <<>> The capacitor charges up to the level of the supply voltage. A capacitor is normally connected across the supply in a piece of equipment fed from a dc source. It is called a decoupling capacitor and it isolates the equipment from outside effects coming in on the supply wires.

Is a run capacitor the same as a start capacitor?

No, they are two different concepts. The start capacitor is used in conjuction with a starting winding on a single-phase induction motor to produce a small component of rotating field inside the motor. This ensures it rotates the desired way. The run capacitor is used to correct the power-factor of the motor, which reduces the current drawn from the supply for the same amount of power.

Can electricity flow in open circuit?

NoAnswerThe answer is YES! For example, if you connect a capacitor (which comprises two metal 'plates' separated by a dielectric or insulator), in series with an AC supply, then a continuous current will flow. If you connect the capacitor in series with a DC supply, then a current will flow for a short period, before the capacitor becomes fully charged.

Does a capacitor store energy in form of an magnetic field?

Current stops going into a capacitor when it's voltage is equal to the supply voltage. From then there is no flow of current, so there is no magnetic field. Yet the capacitor remains charged and has energy to release if required.

What is the use of reactors in capacitor bank panels?

Reduce the harmonic current in the electrical supply system.

Why does capacitor supply reactive power?

A capacitor needs current to flow into and out of it before a voltage is developed across it, so in an ac circuit the current in a capacitor is 90 degrees or a quarter-cycle in front of the voltage. In a 50 Hz system the cycle period is 20 milliseconds so the current peak is 5 milliseconds before the voltage peak every time. The energy in the capacitor is the charge times the voltage, and energy flows into the capacitor and back into the supply twice per cycle. No net energy is dissipated in the capacitor. All the energy is reactive, in other words it flows in and out. The power-factor of the capacitor seen as a load is zero.

Why power factor of capacitor is leading?

In the ac waveform of a capacitor the current waveform leads the voltage waveformcurrent is large to start until capacitor fills with it's voltage charge if that helpsAnswerThe terms 'leading' and 'lagging', used when describing power factor, are defined in terms of whether the load current is leading or lagging the supply voltage.In a capacitive circuit, the load current leads the supply voltage, so the power factor is leading.

Does a capacitor work on ac alternating current?

A capacitor has uses in both AC and DC circuits. A capacitor will block DC current when used in series, but allow an AC signal through. A capacitor used in parallel across a power supply, can be used as storage, maintaining a level DC and conducting AC interference to ground.

How do you determine the size of acapacitor in a rectifier circuit?

ANSWER In rectifiers for power supplies, the capacitor size is determined by the allowable ripple on the output. This can be determined by the rate at which the capacitor is drained. Specifically, this rate is the current drawn from the capacitor. Assume a half wave rectifier made from four diodes. For part of the cycle, the output current is supplied by the rectifier diode. This is also when the capacitor is charged. While the rectifier is not supplying current -- when the input waveform has dropped below the output voltage -- the capacitor must supply the current. Then, as the input waveform rises above the capacitor voltage, the rectifier supplies the current to charge the capacitor and the output circuit.

Why capacitors cannot be used with direct current?

DC does not travel through a capacitor for long because there is a buildup of charge on the plates and when the voltage matches the supply voltage, mo more current flows. But capacitors are used to smooth a DC supply because a capacitor acts a bit like a small battery and can prevent any rapid fluctuations in the supply voltage.

How capacitor and resitor in a circuit effect the phase of input voltage?

A capacitor and a resistor has no effect on the supply voltage; however, this particular load combination will cause the load current to lead the supply voltage by some angle termed the 'phase angle'.

Why capacitor block dc?

capacitor oppose a changein voltage across them by supply current as they discharged or charged. the flow of current through a capacitor in thus directly proportional to the rate of change of voltage across it. this is given by the relation i=c*de/dt where de/dt is the instantaneous change in voltage.

When a series circuit comprising of a resistor and a capacitor is connected to an AC supply the current will?

The load current will lead the supply voltage by some angle greater than zero degrees, but less than 90 degrees.

What effect capacitor has on alternating current ac?

A purely capacitive load causes the load current to lead the supply voltage by 90 electrical degrees. In practise, however, there will always be some degree of resistance in a load, so we call such loads 'resistive-capacitive' (R-C), and the load current will lead the supply voltage by less than 90 elecrical degrees.The capacitance of the capacitor causes it to oppose the load current due to its capacitive reactance (expressed in ohms) -which is inversely-proportional to the frequency of the supply voltage. The higher the frequency, the lower the capacitive reactance.To summarise, a capacitor will act cause the load current to lead the supply voltage, and it will oppose the current due to its capacitive reactance.

Why does DC not flow through a capacitor?

Actually, neither d.c. nor a.c. current passes through a capacitor. A.C. current 'appears' to flow through a capacitor but, in reality, it is only flowing through the connecting circuit while what is known as a 'displacement current' (actually, a distortion of the atoms' shells rather than a conduction current) occurs within the dielectric separating the capacitor's plates. D.C. current is 'blocked' by a capacitor because, when the capacitor is fully charged, the potential difference appearing across its plates is equal and opposite that of the supply. With no net potential difference in the circuit, no current can flow.

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