How to calculate the transformer with capacitor?

Capacitance buck calculation method: For example, we connect a 110V 8W bulb with a 1UF capacitor in series, and when connected to a 220V 50Hz AC voltage, the bulb is lit up to emit normal brightness without being burned. Because the current required for a 110V 8W bulb is 8W 110V = 72mA, it coincides with the current limiting characteristic produced by a 1UF capacitor.

In the same way, we can also connect a 5W 65V bulb with a 1UF capacitor in series to a 220V 50Hz AC, and the bulb will also be lit up without being burned. Because the working current of a 5W 65V bulb is also about 70mA. Therefore, capacitive step-down is actually using capacitive reactance current limiting.

Capacitors, on the other hand, actually play a role in limiting the current and dynamically distributing the voltage across the capacitor and the load.

The working principle of capacitor bucking is not complicated. Its working principle is to limit the maximum operating current by using the capacitive reactance generated by a capacitor at a certain AC signal frequency. For example, at a power frequency of 50 Hz, a capacitive reactance of a 1 UF capacitor is about 3180 ohms.

When a 220V AC voltage is applied to both ends of the capacitor, the maximum current flowing through the capacitor is about 70mA. Although the current flowing through the capacitor is 70mA, it does not produce power dissipation on the capacitor because if the capacitor is an ideal capacitance, the current flowing through the capacitor is the imaginary current, and the work it does is reactive power. According to this characteristic, if we connect another resistive element in series on a 1uf capacitor, the voltage obtained by the resistive element and the power consumption generated by it depend entirely on the characteristics of the resistive element.

The required compensation capacity can be calculated by the following formula: Equation 1: qc=p( 1 cos2 1 cos =p(tg 1 tg)(kvar) Formula 2:

qc=p（ 1 / cos 2 φ1 －11－cos2φ /cosφ）-1 / cos 2 φ 1 ）=p（tgφ1-tgφ）。

where cos 1: power factor before compensation cos: power factor qc:

Required compensation capacity (kvar) p: total line power (kw) The power factor before compensation can be measured by the power factor table, or calculated by electricity consumption: Power factor Active power root number Active power square Reactive power square Because sometimes, the size of the load and the power factor are really not easy to calculate accurately, so the general design department will make up 30%-40% according to the rated capacity of the transformer.

The transformer capacity is estimated, 15% 30%SN is about 20% for a single motor. It should be determined by looking at the nature of your load and the nature of your power supply (transformer). The public transformer generally adopts 8% and 15% (practice has proved that this compensation requirement is low), and the equipment with large inductive load is compensated with the local random follower; As for the special transformer, it should be calculated according to the nature and size of the user's load.

The general formula for capacitance: c=q u

The special formula for parallel plate capacitors: the electric field strength between the plates e=u d

Capacitor capacitance determination c= s 4 kd

1. For a capacitor, if the potential difference between the two stages is 1 volt when the amount of power with 1 bank, the capacitance of this capacitor is 1 method, that is: c=q u

2. But the size of the capacitance is not determined by q (charged) or u (voltage), that is: c = s 4 kd. where is a constant, s is the area facing the capacitive plate, d is the distance of the capacitor plate, and k is the electrostatic force constant.

For common parallel plate capacitors, the capacitance is c= s d( is the dielectric constant of the medium between the plates, s is the area of the plates, d is the distance between the plates.) ）

3. The formula for calculating the electric potential energy of the capacitor: e=cu 2 2=qu 2

4. The calculation formula of multi-capacitor parallel: c=c1+c2+c3+....+cn Multi-capacitor series calculation formula: 1 C=1 C1+1 C2+....+1/cn

5. The obstructive effect of the capacitor on the alternating current with high frequency is reduced, that is, the capacitive reactance is small, on the contrary, the capacitive reactance generated by the capacitor on the alternating current with low frequency is large; For AC capacitors of the same frequency, the larger the capacitance, the smaller the capacitive reactance, and the smaller the capacitance, the greater the capacitive reactance.

6. Series voltage divider ratio: the larger the capacitance, the smaller the voltage of the parallel shunt ratio: the larger the capacitance, the greater the passing current.

7. When t=rc, capacitance voltage=; When t=2rc, capacitance voltage=; When t=3rc, capacitance voltage=; When t=4rc, capacitance voltage=; When t=5rc, capacitance voltage=; t unit, s r unit, ohm, c unit, f

8. Voltage at time t: vt=v0+(v1-v0)*[1-exp(-t rc)].

Formula: i p (root 3 u), i represents the current, the unit is "ampere" (a); p represents the rate of gongdan, unit: reactive power "thousand fatigue" (kvar), active "kilowatt" (kw); Root 3 is approximately equal to; u stands for voltage, measured in kilovolts (kv).

i 40 (of the electric cavity capacity), i .

i 40 (capacitance), i .

Points to note when calculating the rated current of a single capacitor.

1. When a single capacitor is three-phase, the rated voltage marked on it is as follows. The main difference between these two annotation methods is that the internal wiring methods of this three-phase capacitor are divided into two types: star type Y and triangle type δ. The voltage added to the three terminals of the three-phase capacitor is the line voltage.

When calculating its rated current, it has nothing to do with 3 on the denominator in the annotation, whether it is the y connection method δ the late shirt method, u is all. Instead of. According to the three-phase electric power p = 3iu, i = p 3u (regardless of star y and triangle δ connection.

COS is not taken into account. P is the rated capacity of the capacitor, and U is the grid line voltage.

Calculation of the resistance of the capacitor:

The two plates of the capacitor are not absolutely insulated from each other, and there is a relatively large equivalent resistance. Therefore, even if the capacitor is fully charged, even if the external part is not connected to the resistor, it will generally be cleaned naturally through its own large resistance after a long time.

The resistance of the capacitor in the AC circuit is called the capacitive reactance mode, which is called xc, and the calculation formula is xc=1 (c)=1 (2 fc), f is the frequency, the unit is hz, and =2 f is the angular frequency, the unit is 1 s.

It can be seen that when =2 f=0, the capacitance anti-modulus xc is infinite, so the capacitance is quite open in the DC circuit.

Capacitors, often referred to as capacitors, are denoted by the letter C. Definition 1: A capacitor, as the name suggests, is a 'container for electricity' and is a device that holds an electric charge.

Product Name: capacitor. Capacitors are one of the electronic components widely used in electronic devices, which are widely used in circuits in terms of DC blocking, coupling, bypass, filtering, tuning loop, energy conversion, control, etc.

Definition 2: A capacitor, any two conductors (including wires) that are insulated from each other and in close proximity to each other form a capacitor.

Capacitors are not the same as capacitors. Capacitance is a fundamental physical quantity, symbol c, and the unit is f (farad).

The general formula c=q u parallel plate capacitor is the special formula: the inter-plate electric field strength e=u d, and the capacitance determination of the capacitor c= s 4 kd

The required compensation capacity can be calculated by bending through the following formula: Equation 1: qc=p( 1 cos2 1 cos =p(tg 1 tg)(kvar) Formula 2:

qc=p（ 1 / cos 2 φ1 －11－cos2φ /cosφ）-1 / cos 2 φ 1 ）=p（tgφ1-tgφ）。Scattering.

where cos 1: power factor before compensation cos: the power factor qc you want to achieve

Required compensation capacity (kvar) p: total line power (kw) The power factor before compensation can be measured by the power factor table, or calculated by electricity consumption: Power factor Active power root number Active power square Reactive power square Because sometimes, the size of the load and the power factor are really not easy to calculate accurately, so the general design department will make up 30%-40% according to the rated capacity of the transformer.

The transformer capacity is estimated, 15% 30%SN is about 20% for a single motor. It should be determined by looking at the nature of your load and the nature of your power supply (transformer). The public transformer generally adopts 8% and 15% (practice has proved that this compensation requirement is low), and the equipment with large inductive load is compensated with the local random follower; As for the special transformer, it should be calculated according to the nature and size of the user's load.

Capacitance calculation formula:

Series-parallel capacity formula for capacitors - series-parallel voltage divider formula for capacitors:

1.Concatenation formula: c = c1*c2 (c1 + c2)2The parallel formula c = c1 + c2 + c3