Safety Capacitance Parameters and Functions and Applications

Safety capacitor:

The safety capacitor is used for such occasions, that is, after the capacitor fails, it will not cause electric shock and does not endanger personal safety.

It includes two types of X-capacitors and Y-capacitors. The x-capacitor is a capacitor that is connected across two lines (LN) of the power line. Generally, a metal film capacitor is used; the Y-capacitor is connected across two lines of the power line and the ground (LE) respectively. The capacitance of NE) is generally paired. Based on the limitation of leakage current, the value of Y capacitance cannot be too large. Generally, X capacitance is uF level and Y capacitance is nF level. X capacitance suppresses differential mode interference and Y capacitance suppresses common mode interference.

What is Safety Capacitance X Capacitance Y Capacitance According to IEC 60384-14, capacitors are divided into X Capacitors and Y Capacitors,

1. X capacitance refers to the capacitor across LN.

2. The Y capacitor refers to a capacitor that spans between LG/NG.

(L=Line, N=Neutral, G=Ground)

The X capacitor is divided into X1, X2, and X3. The main differences are:

1. X1 high pressure greater than 2.5 kV, less than or equal to 4 kV,

2. X2 withstands high pressure less than or equal to 2.5 kV

3. X3 withstands voltage less than or equal to 1.2 kV

The Y capacitor is subdivided into Y1, Y2, Y3, and Y4. The main differences are:

1. Y1 high pressure greater than 8 kV,

2. Y2 high pressure greater than 5 kV,

3. Y3 high pressure n/a

4. Y4 high pressure greater than 2.5 kV

Both X and Y capacitors are safety capacitors. The X line between the live line and the neutral line is the Y capacitor. They are used in the power supply filter and act as a power supply filter, which filters the common-mode and differential-mode workers separately.

The safety capacitor is used for such occasions, that is, after the capacitor fails, it will not cause electric shock and does not endanger personal safety. Safety Capacitance Safety Level Permissible peak pulse voltage in applications Overvoltage class (IEC664) X1> 2.5kV ≤ 4.0kVIIIX2 ≤ 2.5kVIIX3 ≤ 1.2kV – Safety capacitance Safety class Insulation type Rated voltage range Y1 Double insulation or reinforced insulation ≥ 250V Y2 basic insulation or additional insulation ≥150V ≤250V Y3 basic insulation or additional insulation ≥150V ≤250V Y4 basic insulation or additional insulation <150V The capacitance of Y capacitor must be limited so as to achieve control under rated frequency and rated voltage. The magnitude of the leakage current flowing through it and the effect on the system EMC performance. GJB151 specifies that the capacity of the Y capacitor should not exceed 0.1uF. In addition to the corresponding voltage tolerance of the grid, the Y capacitor also requires a sufficient safety margin in terms of electrical and mechanical properties of the capacitor to avoid breakdown short-circuit phenomena in extremely harsh environmental conditions. The Y-capacitor withstand voltage performance Protection of personal safety is of great importance. X-capacitors are on the filter circuit, which is the LN line. The Y-capacitor is the NG line.

There are X1, X2 and X3 capacitors according to the pulse voltage on the safety standard; points Y1, Y2 and Y3 according to the insulation class.

(These are not classified according to what material, more learning later.)

As for safety standards, there are some differences among countries, but the rated voltage is nothing more than 250 and 400.

All major manufacturers to do the safety capacitor is to meet the requirements of this safety standard, an safety capacitor can meet the requirements of the Y capacitor, but also can be made to meet the X capacitor requirements. So there is a safety capacitor superscript X1Y1, X1Y2. . .

The capacitance between the live line and the zero line is X, and the capacitance between the live line and the ground line is like a Y.

Because of the direct capacitance between the live wire and the 0 wire, it is affected by the voltage peak to avoid short circuit. The more important parameter is the withstand voltage level. There is no limit value on the capacitance value.

The direct line capacitance between the live line and ground line relates to the problem of leakage safety. Therefore, the parameter it pays attention to is the insulation level. As james bai puts it, too large capacitor capacitance will affect the device after the power is cut off.

The capacitance of Y capacitor must be limited to achieve the purpose of controlling the magnitude of the leakage current flowing through it and the effect on the EMC performance of the system under the rated frequency and rated voltage. GJB151 specifies that the capacity of the Y capacitor should not exceed 0.1uF. In addition to the corresponding voltage tolerance of the grid, the Y capacitor also requires a sufficient safety margin in terms of electrical and mechanical properties of the capacitor to avoid breakdown short-circuit phenomena in extremely harsh environmental conditions. The Y-capacitor withstand voltage performance The protection of personal safety is of great importance.

one. Capacitors for suppressing electromagnetic interference in power supplies When capacitors are used in power supply crossover circuits to eliminate noise, not only normal voltages but also abnormal pulse voltages (such as lightning) must be considered, which may cause the capacitors to emit smoke or cause fire. . Therefore, safety standards for cross-line capacitors are strictly regulated in different countries, so capacitors that have been safely certified must be used.

two. Do not use DC capacitors as cross-line capacitors:

The capacitor used for suppressing the power electromagnetic interference of class X2 shall be suitable for applications where the risk of electric shock will not be caused when the capacitor fails. For example, if the power supply is connected across the line, the pulse voltage of 2.5 kV can be tolerated.

For Y2 type suppression of power supply electromagnetic interference capacitor should be applied to the occasion of the capacitor failure does not cause the risk of electric shock, for the power supply across the line connection, can withstand 5kV pulse voltage shock, will not cause breakdown phenomenon.