X capacitors and Y capacitors presentation
Source：http://golpkh.cnRelease time：2015-08-31 10:06:48Views：Keywords：
capacitors
AC power input, the general need to increase the three security capacitance to suppress EMI conducted interference. AC power input is divided into three terminals: FireWire (L) / neutral (N) / ground (G). Between line and neutral suppression capacitor in parallel, commonly known as X capacitors. Because of this capacitor is connected location is also more critical, also need to comply with the relevant safety standards. X capacitor capacitance also belong to one of security. According to actual needs, X capacitance is larger than allowed Y capacitor capacitance values, but this must be at the ends of the X capacitor in parallel with a safety resistor is used to prevent the power cord plug, due to the charging and discharging process of the capacitor and cause the power cord for a long time live. Safety standards, when working among the machine's power cord is unplugged, within two seconds, the power cord at both ends of the charged voltage (or ground) must be less than 30% of the original nominal operating voltage.
Between the line and the ground and between the neutral and ground, and then the capacitance, generally referred to as Y capacitors. The two Y capacitors connected more critical position, must comply with the relevant safety standards required to prevent leakage or cause electronic equipment enclosure charged, likely to endanger the personal safety and lives. They all belong to security capacitance, requiring capacitance value can not be too large, while the pressure must be high. In general, working in the subtropical machine requires earth leakage current must not exceed 0.7mA; in temperate machine requires earth leakage current must not exceed 0.35mA. Therefore, the total capacity of the Y capacitors are generally not exceed 4700PF (472).
In particular:
As one of the X capacitor safety capacitor, must obtain certification also requires safety testing agencies. X capacitors are generally marked with a safety certification mark words and voltage AC250V or AC275V, but its true DC voltage up to 2000V or more, use the time not free to use voltage AC250V or DC400V like ordinary nominal capacitance substitute. As a safety capacitor Y capacitor, security requirements must be certified testing organizations. Y-capacitors look more orange or blue, generally marked with safety certification mark (such as UL, CSA and other identification) Pressure AC250V or words and AC275V. However, the real DC voltage up to 5000V or more. It must be emphasized, Y capacitors are not free to use voltage AC250V or DC400V like ordinary nominal capacitance to substitute.
Typically, X capacitor ripple current multi-use resistance larger class polyester film capacitors. This type of capacitor, larger, but it allows instantaneous charge and discharge current is also large, and the resistance is correspondingly smaller. Ordinary capacitor ripple current indicators are very low, a high dynamic resistance. X capacitors instead of using ordinary capacitors, capacitor voltage can not be met in addition to standard addition, the ripple current indicators also difficult to meet the requirements.
According to IEC 60384-14, the capacitor is divided into X capacitors and Y capacitors,
1. X capacitor refers to a capacitor cross between L-N,
2. Y means across the capacitor capacitance between L-G / N-G's.
(L = Line, N = Neutral, G = Ground)
Under the X capacitor is divided X1, X2, X3, the main difference is:
1. X1 high pressure greater than 2.5 kV, less than equal to 4 kV,
2. X2 high pressure less than or equal 2.5 kV,
3. X3 high pressure is less than equal to 1.2 kV
Under the Y capacitor is divided into Y1, Y2, Y3, Y4, the main difference is that: (resistant DC voltage level)
1. Y1 high pressure is greater than 8 kV,
2. Y2 high pressure is greater than 5 kV,
3. Y3 high pressure n / a
4. Y4 high pressure greater than 2.5 kV
They are used in power filters in, play a role in the power filter, respectively, common mode and differential mode interference workers from the filtering effect.
On the capacitance means for such occasions, that is, after failure of the capacitor will not cause electric shock, do not endanger their personal safety. It includes the X capacitors and Y capacitors.
x capacitor is connected across the power line between the two lines (LN) capacitors, generally used in the metal film capacitors; Y capacitors are respectively connected across two lines between the power line and the ground (LE, NE) capacitors, usually in pairs ??? Based leakage current limit, Y capacitance value can not be too large, general X-uF capacitor is level, Y nF capacitor is level. X capacitor differential mode interference suppression, Y capacitors suppress common mode interference.
Safety capacitor Safety class
Safety capacitor Safety class applications permitted peak pulse voltage overvoltage category (IEC664)
X1> 2.5kV ≤4.0kV Ⅲ
X2 ≤2.5kV Ⅱ
X3 ≤1.2kV -
Safety capacitor Safety class type of insulation rated voltage range
Y1 double or reinforced insulation ≥ 250V
Y2 basic or supplementary insulation ≥150V ≤250V
Y3 basic or supplementary insulation ≥150V ≤250V
Y4 basic or supplementary insulation <150V
Y capacitor capacitance must be limited so as to control at the rated frequency and rated voltage is applied, the flow through the size of its leakage current and affect system performance for EMC purpose.
GJB151 provisions of Y capacitor value should be less than 0.1uF. Y capacitors in addition to meeting the corresponding grid voltage withstand, but also requires such a capacitor has sufficient safety margin in the electrical and mechanical properties, to avoid short-circuit breakdown phenomenon in extreme environmental conditions, pressure resistance of Y capacitors protect the personal safety is important.
Then add that choice should pay attention to:
I. electromagnetic interference suppression capacitors
When using a capacitor in the power supply across the line circuit to eliminate noise, not only the normal voltage, it must also take into account the abnormal pulse voltage (lightning) generation, which may cause the capacitor to smoke or fire. Therefore, the safety standard across the line, there are strict regulations for capacitors in different countries, it must go through safety certification using a capacitor.
Second, do not allow the DC capacitor is used across the line capacitor use:
For class X2 electromagnetic interference suppression capacitors should apply when the capacitor failure does not cause an electric shock hazard situations, such as power jumper line connection, it can withstand the impulse voltage 2.5kV.
Y2 class for electromagnetic interference suppression capacitors should be applied when the capacitor failure does not cause an electric shock of the occasion, for power across the line connection, can withstand the shock pulse voltage 5kV, the breakdown will not occur. 1. X capacitors, polystyrene (vinyl film) capacitors, high voltage resistant polystyrene, suitable for EMI circuit, high-voltage pulse absorption.
2. The capacity calculation: general levels X capacitor, the previous level with 0.47uF, the second group with a 0.1uF; 0.47uF single stage is not yet quite easy to use calculation methods. (Capacitance of the size and power of power no direct relation)
X capacitors are said peak voltage than the rated voltage, X capacitors are generally used MPX (metalized polypropylene mode capacitor) their rated voltage is several hundred volts, An X2 labeled MPX-X2-250VAC / 275VAC.
