What is safety capacitors

The reason why safety capacitors are called safety regulations refers to their use in situations where the failure of the capacitor will not cause electric shock or endanger personal safety. The safety capacitor includes two types: X capacitor and Y capacitor. Unlike ordinary capacitors, even after the external power supply is disconnected, the stored charges inside the ordinary capacitor will remain for a long time, but the safety capacitor will not have this problem.

 

It is also an important filter capacitor in the circuit. The majority of safety capacitors are blue, yellow, gray, and red.

 

Normally the X capacitor is yellow, and the Y capacitor is blue of UF Capacitors

 

 

 

The role of safety capacitors in switching power supplies

 

1: X safety capacitor, the most commonly used is X2 safety capacitor, and some will use X1 capacitor.

The X2 capacitor is mainly connected in parallel between the power grid, that is, between the live and zero lines of the wires. This type of capacitor can filter out series mode interference (also known as differential mode interference) between the power grid lines. The higher the rated voltage of the X2 capacitor, the higher it becomes. The lowest in the industry is 275VAC, the moderate is 310VAC, and the better rated voltage is 350/380VAC. The higher the rated voltage, the more margin, the longer the lifespan, and the better the filtering effect.

Anti electromagnetic interference is the most common function of X capacitors. Generally, two pins are connected across the zero and live wires, suitable for high-frequency, DC, AC, coupling, and bridging

pulse circuits. They can withstand overvoltage impacts and are generally used in parallel with resistors to discharge charges

Resistance-capacitor voltage reduction is also commonly used in X capacitors, especially for low-cost finished products. The working principle of capacitor voltage reduction is to use the capacitance generated by the capacitor at a certain AC signal frequency to limit the maximum working current. If a resistive element is connected in series to a capacitor at the same time, the voltage obtained at both ends of the resistive element and the power consumption generated by it depend entirely on the characteristics of the resistive element. Therefore, capacitor voltage reduction is actually achieved by utilizing capacitive reactance to limit current, while capacitors actually play a role in limiting current and dynamically distributing voltage between capacitors and loads

2、The most commonly used safety Y capacitors are Y1 and Y2 safety capacitors

The main function of the Y capacitor is to suppress common mode interference, which can filter out the common mode interference generated by the coupling capacitance of the primary and secondary windings. It is called the "Y capacitor", with one end connected to the DC high voltage on the primary side and the other end connected to the common terminal on the secondary side (used to filter out high-frequency interference in the 10-200MHz frequency band, so short leads are needed for connection. The commonly used capacity range is 1-2.2nF, and the withstand voltage value is generally not less than 1.5kV).

Many isolated switching power supplies add Y capacitors to the primary and secondary to provide a loop to the common mode current of the secondary, reducing the impact of the common mode current on the output. Y capacitors are connected in series between high voltage ground and low voltage ground. Sometimes, two Y capacitors are used in series to improve the voltage resistance between high voltage ground and low voltage ground. Sometimes, there may be insufficient voltage resistance, resulting in the safety capacitor not being able to withstand the voltage. High voltage ceramic capacitors can be used as Y capacitors.

On general switching power supplies, X and Y capacitors need to be used together to protect user safety and EMC filtering

 

Can switching power supply not use safety capacitors?

 

In theory, even if safety capacitors are not used, they can still be used, but the lifespan of the power supply will be shortened (there may be abnormal pulse voltages such as lightning in the power supply, which may cause damage to the switch capacitor). At the same time, the power supply itself also needs to pass safety certification. If safety capacitors are not used, the power supply itself cannot pass safety regulations, so safety capacitors on the switch power supply are essential

 

Application of safety capacitors

 

The application of safety capacitors is very extensive:

small household appliances,

power supply products,

electromechanical motors,

LED lighting,

chargers,

uninterrupted power supplies, etc

 

Certification type

 

No matter what components are, as long as they are legitimate, they must have certification. Safety certification also includes product safety certification, environmental certification, and energy certification. Different countries have different safety regulations, and some require mandatory certification. There are many certifications, such as China's CQC certification, Germany's VDE certification, the United States' UL certification, the European Union's ENEC certification, and Korea's KC certification. When selecting safety capacitors, different certified components should be selected according to different occasions and countries

UF Capacitors safety capacitors have obtained certifications such as CQC, VDE, UL, etc

UF Capacitors produces high quality Safety capacitors, we offer alternative to replace big brand with Much better prices and shorter lead time 

 

Here are some cross reference from UF Capacitors:

 

X2 cross reference:

 

P/N of UF Capacitors	Description  of UF Capacitors	P/N of Competitor
X2F105KA3100150B000	X2 1uF 310VAC +/-10% P: 15mm Bulk RoHS	F861BZ105M310A
X2F225KA3100225B050	X2 2.2uF 310VAC +/-10% P:22.5mm Bulk RoHS	F861DU225K310Z
X2F683KA3100150B035	X2 0.068uF 310VAC +/-10% P: 15mm Bulk RoHS	BFC233620683
X2F823KA2750100B000	X2 0.082uF 275VAC +/-10% P:10mm Bulk RoHS	MPX823K310ACC3
X2F334KA275S150B040	X2 0.33uF 275VAC +/-10% P:15mm Bulk RoHS	890324025034CS

 

Y1 cross reference:

 

P/N of UF Capacitors	Description  of UF Capacitors	P/N of Competitor
Y1U102MA5000100B000H	Y1 1000PF 500VAC Y5U +/-20% Bulk RoHS Halogen free,Straight lead	YU0AS102M080L20C0H
Y1U222MA4008100A000H	Y1 2200pF 400VAC  Y5U +/-20% P:10mm  Ammo RoHS Y Kinked  Halogen free	DE1E3KX222MN4AN01F
Y1U102MA5008100A000	Y1 1000PF 500VAC +/-20% Y5U P: 10mm Ammo RoHS Y Kinked	VY1102M35Y5UQ6TV0
Y1Z332MA5008100B000	Y1 3300pF 500VAC  Y5V +/-20% P:10mm Bulk RoHS Y Kinked	VY1332M43Y5VQ6BV0
Y1P221KA5008100A000	Y1 220pF 500VAC Y5P +/-10% P:10mm Ammo RoHS Y Kinked	VY1221K31Y5SQ6TV0

 

Y2 cross reference:

 

P/N of UF Capacitors	Description  of UF Capacitors	P/N of Competitor
Y2U222MA2500075B000	Y2 2200pF 250VAC Y5U +/-20% P: 7.5mm  Bulk RoHS Straight lead	WYO222MCMYA0KR
Y2U102MA2502075B000	Y2 1000pF 250VAC Y5U +/-20% P:7.5mm  Bulk RoHS outside lead	YU0AC102M060X
Y2U472MA2500075B000	Y2  4700pF 250VAC Y5U +/-20% P;7.5mm Bulk RoHS straight lead	WYO472MCMCF0KR
Y2Z103MA2508075A000	Y2 0.01uF 250VAC Y5V +/-20% P:7.5mm Ammo RoHS Y Kinked	DE2F3KH103MN7A
Y2P471KA2508075A000	Y2 470pF 250VAC Y5P +/-10% P:7.5mm Ammo RoHS  Y Kinked	DE2B3KH471KN3A

 

How to Obtain a Quote from UF Capacitors? 

 

You can easily send an email to lily@ufcapacitors.com, the engineering and sales team in UF Capacitors will help you select the correct polymer aluminum capacitors.

 

For more details, pls visit our website: www.ufcapacitors.com