jbcapacitors blog

Jun, 1980, founded in Tainan, Taiwan to produce Plastic Film Capacitors.
Feb, 1982, started to produce Snap-in, Screw & Lug type Aluminum Electrolytic Capacitors.
Dec, 1984, established sales office and warehouse in Hong Kong Located in N.T., HK
July, 1987, moved to China and built up joint venture in Hefei, Anhui Province, China.
Dec, 1988, started production of Snap-in, Screw & Lug Aluminum Electrolytic Capacitors in China.
Dec, 1988, started production of Snap-in, Screw & Lug Aluminum Electrolytic Capacitors in China.
Aug, 1993, jb Capacitors became sole proprietorship enterprise in China.
Jun, 2003, jb Capacitors set up sales office in Dongguan, Guangdong Province, China.
March, 2005, started to produce SMD Aluminum Capacitors.

Aluminum is used for the electrodes by using a thin oxidization membrane. Large values of capacitance can be obtained in comparison with the size of the capacitor, because the dielectric used is very thin. The most important characteristic of electrolytic capacitors is that they have polarity. They have a positive and a negative electrode.[Polarised] This means that it is very important which way round they are connected. If the capacitor is subjected to voltage exceeding its working voltage, or if it is connected with incorrect polarity, it may burst. It is extremely dangerous, because it can quite literally explode. Make absolutely no mistakes.

Generally, in the circuit diagram, the positive side is indicated by a "+" (plus) symbol.

Electrolytic capacitors range in value from about 1µF to thousands of µF. mainly this type of capacitor is used as a ripple filter in a power supply circuit, or as a filter to bypass low frequency signals, etc. Because this type of capacitor is comparatively similar to the nature of a coil in construction, it isn't possible to use for high-frequency circuits. (It is said that the frequency characteristic is bad.)

Description :

1. High frequency operation.
2. High du / dt.
3. High insulation resistance.
4. Flame retardant epoxy resin (UL 94V-0).

Specification :

1. Operating temperature: -40℃~+100℃.
2. Capacitance range: 0.0022μF~1μF.
3. Capacitance tolerance: ±10% (K).
4. Rated voltage: 300V, 280V, 275V. 250V.AC
5. Dissipation factor: 0.08% max at 1KHz 20℃ 0.3% max at 10KHz 20℃.
6. Insulation resistance: 1.R≥30,000MΩ (C≤0.33μF) 1.R≥10,000MΩ (C>0.33μF)

These Metallized Polypropylene Capacitors are specifically designed for high current, high frequency applications like switching power supplies. Film capacitors offer a much higher degree of reliability and stability than other types of capacitors. Polypropylene capacitors are non-polar, they come in the all case styles, including Wrap & Fill, Epoxy Case, and Metal Hermetically Sealed.

Metallized Polypropylene capacitors have high current end terminations to handle high pulse currents as well as high RMS currents. Detailed specifications as well case sizes for our standard Axial Wrap & Fill are linked www.jbcapacitors.com For custom designs please contact our sales with your specific requirements as we specialize in custom made capacitors.

All capacitors have a voltage rating. This tells you how much voltage the dielectric (insulator) can withstand before allowing DC to pass between its plates. Sometimes a capacitor has a working voltage (i.e. WVDC working voltage DC) and a surge voltage. The working voltage tells you how much voltage the capacitor can withstand long term (for the normal life of the capacitor). The surge voltage is the voltage is can withstand for short periods of time. Generally, if too much voltage is applied to a capacitor, it will fail. In electrolytic capacitors, the forming voltage (voltage used to anodize the plates) and the thickness of the paper element determine the working voltage of the cap. In film type capacitors, the insulating material (polyethylene, polypropylene...) will determine the maximum working voltage.

The aluminum foil that makes up the plates in the electrolytic capacitor is treated in a few different processes to make it work properly and more efficiently. The most important process is the anodizing of the foil. Anodizing is a process that forms a very thin layer of aluminum oxide on one or both sides of the foil when the foil is immersed in an acidic solution and direct current is applied to the foil (one lead of the DC power supply is connected to the foil and the other is connected to a conductive plate in the acidic solution). This layer of aluminum oxide is the dielectric (insulator) and serves to block the flow of direct current. To increase the surface area on the foil (and ultimately increase capacitance), the foil can be etched by a chemical process. This would be done before the anodizing.

Electrolytic caps are more complex than film capacitors and are generally used for larger capacitance values (0.47 microfarad and higher). The electrolytic capacitor generally consists of 2 layers of aluminum foil with a layer of paper material between the plates. It looks a little like this:

When a DC voltage source is applied to a capacitor there is an initial surge of current, when the voltage across the terminals of the capacitor is equal to the applied voltage, the current flow stops. When the current stops flowing from the power supply to the capacitor, the capacitor is 'charged'. If the DC source is removed from the capacitor, the capacitor will retain a voltage across its terminals (it will remain charged). The capacitor can be discharged by touching the capacitor's external leads together. When using very large capacitors (1/2 farad or more) in your car, the capacitor partially discharges into the amplifier's power supply when the voltage from the alternator or battery starts to fall. Keep in mind that the discharge is only for a fraction of a second. The capacitor can not act like a battery. It only serves to fill in what would otherwise be very small dips in the supply voltage.

Vibration Test:

Test condition E for 720P, test condition B all others; no mechanical damage, short, open or intermittent circuit.

Moisture Resistance:

The hermetically sealed units shall be tested as outlined in the Moisture Resistance testing of section J. As a result of the test there shall be:

• No visible damage
• Max. ∆ C of ± 0.25%
• Min. IR = 33% of initial limit
• Max. DF = 0.12%

Capacitive reactance (symbol Xc) is a measure of a capacitor's opposition to AC (alternating current). Like resistance it is measured in ohms, Ω, but reactance is more complex than resistance because its value depends on the frequency (f) of the electrical signal passing through the capacitor as well as on the capacitance, C.

The reactance Xc is large at low frequencies and small at high frequencies. For steady DC which is zero frequency, Xc is infinite (total opposition), hence the rule that capacitors pass AC but block DC.

For example a 1µF capacitor has a reactance of 3.2kΩ for a 50Hz signal, but when the frequency is higher at 10kHz its reactance is only 16Ω.

Note: the symbol Xc is used to distinguish capacitive reactance from inductive reactance XL which is a property of inductors. The distinction is important because XL increases with frequency (the opposite of Xc) and if both XL and Xc are present in a circuit the combined reactance (X) is the difference between them.