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Polyester film capacitor is often referred to as CL capacitor. Their common feature is that they are all wound with metallized polyester film, such as common CL21 capacitor, CL21X capacitor, CL20 axial capacitor, etc. 

What classification and function does metallized polyester film have? Here is a detailed introduction.

Metallized film is to evaporate aluminum or zinc aluminum to the surface of the film in vacuum. 
The material has high dielectric constant, high insulation resistance, good heat resistance and tensile resistance, which is suitable for making metallized polyester film capacitors.

Common classification of metallized polyester film:

Aluminum metallized polyester film with single side and single edge
Aluminum metallized polyester film with double side and single edge
Single side multi string aluminum metallized polyester film
Single side single edge zinc plus aluminum metallized polyester film

The characteristics of metallized polyester film capacitor are as follows:

It has the advantages of wide capacity range, small volume (smaller than polypropylene film capacitance), high temperature resistance (up to 120 ℃), light weight, relatively low price, good self-healing property. Some small capacity can be produced by series metallized film, with high pressure resistance, high temperature wax inner sealing, flame retardant epoxy powder sealing, stable moisture resistance and low noise.

The metallized polyester container has self-healing characteristics, that is, if there is a defect in the plastic film of the capacitor, it will break down when voltage is applied, then the metal film here will evaporate, and there will be no short circuit phenomenon, so that the capacitor can still work normally.

Disadvantages: metallized ester film capacitor is not resistant to high frequency, and the loss is larger at high frequency.

The function of metallized polyester film capacitor is as follows：

It is suitable for DC isolation, bypass and coupling. It is widely used in filtering low pulse circuit.

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According to the media materials:Polypropylene PP, Polyester PET, Polyphenylene sulfide, Poly (naphthalene ethyl ester) PPS, PEN, Polystyrene PS, Polytetrafluoroethylene PTFE, Polycarbonate PC and paper, Acrylic resin

Paint film and so on.

According to the electrode: metal foil, metallization (also divided into aluminum, zinc, zinc aluminum, copper metallization), and the mixed form of the two

According to package: no package, epoxy resin package, plastic shell package, metal shell package, etc

WEET CL20 WMB Series 250V metallized polyester film flat axial capacitor (metallized polyester film capacitor), with metallized polyester film as medium and electrode, wrapped with flame retardant tape and sealed with epoxy resin, has excellent electrical performance, good reliability, high temperature resistance, small volume, large capacity and good self-healing performance. 
It is suitable for AC and DC circuits of instruments and household appliances, and widely used in audio system frequency division circuit.

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WEET WMB 100V MET/MEA(CL20) Capacitors Cross Reference To jbCapacitors, CDE, Vishay and EPCOS TDK B32231

JFG - Axial Metallized Polyester & Polypropylene Film Capacitor

https://www.jbcapacitors.com/Plastic-Film-Capacitors/JFG-Axial-Metallized-Polyester-Polypropylene-Film-Capacitor.html

CDE / Illinois Capacitor
https://www.mouser.com/datasheet/2/88/MWR_series-553021.pdf

Vishay DC Film Capacitors MKT Axial Type MKT1813
https://www.vishay.com/docs/26013/mkt1813.pdf

EPCOS / TDK B32231 Series Film Capacitors
https://www.tdk-electronics.tdk.com/inf/20/20/db/fc_2009/B32231.pdf

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WEET DC Film Capacitors MKT CL20 Axial Flat Type 100V 250V 400V 630V For Audio Hifi Applications
How to understand the Series number of Chinese capacitors?

Capacitor is one of the most widely used electronic components in electronic equipment. It is widely used in isolation, coupling, bypass, filtering, tuning circuit, energy conversion, control circuit and so on.
Frequency characteristics of capacitor: with the increase of frequency, the capacitance of general capacitor presents a law of decline.

Naming method of capacitor model: (according to GB2470-81)
The first part: letter the product name C
The second part: the medium materials of products are indicated by letters

A: tantalum electrolysis 
B: nonpolar film 
C: high frequency ceramics 
D: aluminum electrolytic capacitors
E: other materials electrolysis 
G: alloy electrolysis 
H: paper film composite 
I: glass uranium 
J: metallized paper dielectric 
L: polyester and other polar organic film 
N: niobium electrolysis 
O: glass film 
Q: paint film 
S, T: low frequency ceramics 
V, X: mica paper y mica 
Z: paper. 

Note: when B is used to indicate other capacitors except polystyrene, a letter should be added after B to separate specific materials. Such as CBBxx
When L is used to represent the capacitance of other films other than polyester, the method is the same. CLxx

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CL refers to a type of film, that is polyester film, then CL capacitor refers to polyester film capacitor. 
The common CL capacitors are as follows: CL21 polyester film capacitor, CL21X ultra small polyester film capacitor, CL20 axial polyester film capacitor, etc.

Advantages of CL polyester film capacitor:

1. Small size.
Compared with CBB polypropylene film capacitor, the size of CL capacitor is smaller under the same capacity and voltage. For some places with high requirements for installation space, this feature of CL capacitor is very practical.

2. Higher temperature resistance.
CBB polypropylene film capacitor better can withstand 105 ℃ high temperature, but CL capacitor can withstand 125 ℃ high temperature, if used in higher temperature occasions, CL capacitor will have some advantages.

3. It's cheaper.
Compared with CBB capacitor, the price of CL capacitor will be slightly lower.

The disadvantages of CL polyester film capacitor are as follows

CL capacitors have both advantages and disadvantages. High loss is its biggest disadvantage, especially in high frequency circuit, which is not as good as CBB capacitor.

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What is the Difference Between Metallized Polyester Film CL Capacitors and Metallized Polypropylene Film CBB Capacitors

Polypropylene film capacitor is an inductive structure, which is made of polypropylene as dielectric and aluminum foil as electrode. The conductor is tinned copper clad steel wire and epoxy polypropylene film capacitor is used.

Characteristics of Polypropylene Film Capacitor:

• Small volume and light weight;

• Better stability and reliability.

• The lead wire is directly spot welded to the electrode with low loss.

• It is widely used in the DC and pulse circuits of TV sets, radio recorders, DVD and various communication equipment and electronic instruments.

Polyester film capacitor is also known as CL capacitor, and polypropylene film capacitor is also called CBB capacitor. The two types of capacitors are well differentiated from each other. 
Generally, polyester film capacitor starts with CL, while polypropylene film capacitor starts with CBB. Both of them have the characteristics of self-healing and insensibility.

The main differences between CL and CBB are as follows:

1. The stability of CBB capacitor is higher than that of CL capacitor at high frequency.

2. Under the same temperature change condition, the range of CBB capacitance changing with temperature is smaller than that of CL capacitance.

3. The loss of CBB capacitor is smaller than that of CL capacitor. At the frequency of 1kHz, the tan δ of CBB capacitor is less than 0.001, while that of CL capacitor is less than 0.01.

4. The insulation performance of CBB capacitor and Cl capacitor is particularly good, which is better than other capacitors, while the insulation performance of CBB capacitor is better than that of CL capacitor. For example, when the capacity is less than 0.33uf, the insulation resistance of CBB capacitor is greater than 25000 m Ω, while that of CL capacitor is greater than 7500 m Ω.

5. Compared with CBB capacitor, CL capacitor  has the advantage of small volume. Under the same voltage and capacity, the volume of CL capacitor can be smaller than that of CBB capacitor, which is very useful for customers with limited installation space.

As CBB capacitor has better performance, but its price is more expensive, so there are many CL capacitors in the market that can not be found out by visual inspection. Therefore, Zongqiang Electronic Engineer recommends the following two methods for your reference:

1. Measure the loss value. If it is less than 0.001, it is CBB capacitor, otherwise it is CL capacitor.

2. Conduct the test with palm digital capacitance meter and hair dryer. First, put the capacitor on the capacitance meter to measure the cold state capacitance value, then heat the capacitor with the air blower, and then measure the capacitance value. If the capacitance value changes too much, it is CL capacitor, otherwise it is CBB capacitor

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CL19 is non inductive structure, which is made of metallized polyester film as electrolyte / electrode. 
The conductor is made of tinned copper clad steel wire, the outer layer is wrapped with polyester tape, and both ends are sealed with epoxy resin.

1. Wide capacity range
2. Small size, light weight
3. Excellent self-healing performance
4. It is suitable for DC and VHF signal isolation, bypass and coupling
5. Widely used in filtering, noise reduction, low pulse circuit

Below is  WEET MKT WMA 100V Axial Lead Metallized Polyester Film Capacitor (CYCLOIDAL) CL19 China Part Number Common values in 100VDC.

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WEET MEA MKT MPE CL19 Axial Metallized Polyester Film Capacitor CYCLOIDAL Round Shape Applications generally are suitable for blocking, by-pass, coupling, and decoupling, also suitable for DC impulse and pulse circuit

WEET WMA type Capacitors are Metalized polyester film, non-inductive type, axial. Small size, light weight, excellent self-healing property. Wrapped with polyester adhesive tape and ends filled. High reliability, high capacitance, excellent electrical

characteristic

WEET WMA Audio Capacitors Main Material and Sturcture.

A: Dielectric : Polyester Film

B: Electrodes : Metal Vapor Coating

C: Encapsulation : PET Tapes(UL94V-0)

D: Epoxy Resin Coating(UL94V-0)

E: Lead : Tinned Copper Clad Steel Wire

F: Metal Spray Layer

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Because it is coated with a metal layer on the porcelain tube, two poles are formed inside and outside. Because the tube is empty, it is called through center capacitance. It is a kind of three terminal capacitor, but compared with the common three terminal capacitor, because it is directly installed on the metal panel, its grounding inductance is smaller, and there is almost no influence of lead inductance. In addition, its input and output terminals are isolated by metal plates, eliminating high-frequency coupling. These two characteristics determine that the through core capacitor has the filtering effect close to the ideal capacitance. Moreover, it is an ideal device for interference filtering.

CBB19 is a non inductive structure, which is wound with metallized polypropylene film as dielectric / electrode. The lead wire is made of tinned copper clad steel wire, the outer layer is wrapped with polyester tape, and both ends are filled with epoxy resin.

How to select the capacitor in the audio circuit. In the audio circuit, there are four capacitors, which are coupling capacitor, frequency dividing capacitor, bypass capacitor and filtering capacitor. WEET engineers will introduce the above four capacitors category in next passage. Please follow us, thank you.

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Strong Items in 630VDC CL19, CL20, CBB19, CBB20:

WEET WAA 1.0uF 630VDC 5% MKT Polyester 

WEET WAB 4.7uF 630VDC 5% MKT Polyester 

WEET WAC 2.2uF 630VDC 5% MKP Polypropylene

WEET WAD 2.2uF 630VDC 5% MKP Polypropylene