In this article, Cucab introduces what is safety capacitor_the difference between safety capacitor and common capacitor, safety capacitor is a safety capacitor that will not lead to electric shock and will not endanger personal safety when the capacitor fails. Safety-rated capacitors are usually used only for filtering in anti-interference circuits. They are used in power filters to play a power filtering role, filtering common mode and differential mode interference, respectively. For safety reasons and EMC considerations, it is generally recommended to add safety capacitors to the power supply inlet.
The safety capacitor is divided into x-type and y-type. The AC power input is divided into 3 terminals: Firewire L/Zero N/Ground, (L=Line, N=Neutral, G=Ground). Across the “L-N”, that is, between the “fire line – zero line” is the X capacitor; Across the “L-G/N-G”, that is, between the “fire line – ground between “L-G/N-G”, i.e. “fire line – ground or zero line – ground” is the Y capacitor. A capacitor between the fire wire and zero wire is like “X”, and a capacitor between the fire wire and ground wire is like a “Y”, these are not divided according to what material.
X capacitor: Because the location of this capacitor connection is also critical, it also needs to meet the relevant safety standards. x capacitor is also one of the safety capacitors. According to the actual needs, the capacitance of the X capacitor is allowed to be larger than the capacitance of the Y capacitor, but at this time must be connected in parallel with a safety resistor at both ends of the X capacitor, used to prevent the power cord unplugged, due to the charging and discharging process of the capacitor and the power cord plug charged for a long time. Safety standards, when the machine is working in the power cord is unplugged, in two seconds, the power cord plug ends charged voltage (or potential to ground) must be less than 30% of the original rated working voltage.
Capacitor de magnetizador de 2kv-1000uf - Capacitor de pulso - Capacitor de magnetizador de alta tensão

Capacitor de magnetizador de 2kv-1000uf - Capacitor de pulso - Capacitor de magnetizador de alta tensão

As one of the safety capacitors, X capacitor is also required to obtain the certification from the safety testing agency. X capacitor is generally marked with safety certification mark and the wording of withstand voltage AC250V or AC275V, but its real DC withstand voltage is up to 2000V or more, so don’t use ordinary capacitors with nominal withstand voltage AC250V or DC400V or so arbitrarily. Usually, the X capacitor uses the mylar film type capacitor with high ripple current. This type of capacitor is larger in size, but its allowed instantaneous charging and discharging current is also large, while its internal resistance is correspondingly small.
Y capacitor: The position of these two Y capacitors connected is more critical and must need to meet the relevant safety standards to prevent causing electronic equipment leakage or enclosure charged, which can easily endanger personal safety and life. They all belong to safety capacitors, thus requiring the capacitance value not to be large, while the withstand voltage must be high. In general, for machines working in subtropical zone, the leakage current to ground should not exceed 0.7mA; for machines working in temperate zone, the leakage current to ground should not exceed 0.35mA; therefore, the total capacity of Y capacitor should not exceed 4700PF (472). GJB151 stipulates that the capacity of Y capacitor should be no more than 0.1uF.
Besides conforming to the corresponding grid voltage withstand voltage, Y capacitor is also required to have enough safety margin in electrical and mechanical performance to avoid breakdown short circuit under extreme harsh environmental conditions, and the voltage withstand performance of Y capacitor is of great significance to protect personal safety. Specially, Y capacitors, as safety capacitors, are required to be certified by safety testing organizations, and they are mostly orange or blue in appearance, usually marked with safety certification marks (such as UL, CSA, etc.) and withstand voltage of AC250V or AC275V. However, their real DC withstand voltage is up to 5000V or more.
It must be emphasized that Y capacitors should not be used as a substitute for ordinary capacitors with nominal withstand voltage of AC250V or DC400V.
The difference between safety-regulated capacitors and ordinary capacitors
The discharging of the safety capacitor is different from the ordinary capacitor. In the AC power input, generally need to add 3 safety capacitors to suppress EMI conducted interference.
Capacitor de magnetizador de 2kv-1000uf - Capacitor de pulso - Capacitor de magnetizador de alta tensão

Capacitor de magnetizador de 2kv-1000uf - Capacitor de pulso - Capacitor de magnetizador de alta tensão

The main difference is that the outer shell is plastic, there are ABS material and TPB material, the flame retardant effect may be better, there is nothing different from the material analysis! There is one more point, the safety capacitor is mainly used to suppress interference, divided into X, Y two types of X capacitors to suppress differential mode interference, generally across the connection and between L and N, divided into four grades. Each grade has a different withstand voltage. It will not be harmful to human body when it fails.
Y capacitor is for suppressing common mode interference, generally connected between L and G, also divided into four grades. Generally there will be leakage current. Circuit selection is generally using a cheaper porcelain chip capacitor, the disadvantage is the leakage current is large. If you use metalized film to make Y capacitor, the cost is higher, but the advantage is that the leakage current is smaller compared with porcelain film capacitor.
Safety-rated capacitors are used for such occasions that the failure of the capacitor will not lead to electric shock and will not endanger personal safety. Safety-rated capacitor safety rating The peak pulse voltage overvoltage rating allowed in the application (IEC664) X1 is greater than or equal to 2.5kV ≤ 4.0kV ⅢX2 ≤ 2.5kV ⅡX3 ≤ 1.2kV, safety-rated capacitor safety rating Insulation type Rated voltage range Y1 Double insulation or reinforced insulation ≥ 250V
Y2 basic insulation or additional insulation ≥150V≤250VY3 basic insulation or additional insulation ≥150V≤250VY4 basic insulation or additional insulation less than or equal to 150V, the failure mode of safety capacitor is open circuit, so it is safe, general capacitor for short circuit.
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