Film capacitors(Metal Oxide Varistor), film capacitor is widely used in the cross-linking of the analog signal, power supply noise bypass (anti-cross-linked) place. The film capacitor When the electrode based on a metal foil, and polyethylene ethyl acrylate, polypropylene, poly stupid plastic film such as vinyl or a polycarbonate, from the overlap of the ends, wound into a cylindrical structure of a capacitor.
Nickname film capacitors
Capacitor categories, called on their models in the market are not uniform:
1, polyester capacitors: usually say polyester capacitors Model: called for PEI in adapting the CL11 to foreign countries or foreign companies or PEM, the main material for polyester film, the full name of the felt-type polyester / ester film capacitors, the price of such a capacitor cheap, small size, electrical performance is not bad, the loss slightly bigger.
2, metallized capacitor: the domestic call CL21, CBB21 (a lot of people capacitor CBB model called CBB capacitor), foreign called MEF and MPP Its main material is polyester metallized film and polypropylene metallized film(Metal Oxide Varistor).
3, CBB capacitor: CBB21, CBB18, CBB81 capacitor collectively, people say CBB capacitor means CBB81 abroad called the PPS metallized polypropylene capacitors within the string type high-pressure, anti-current voltage capability, loss is the safest choice of most engineers, the drawback is that expensive, bulky, feet away from the general in 15,20 mm.
4, polyester capacitors and polypropylene capacitors: called raw materials for capacitors, CL is a polyester material, CBB polypropylene material.
The thin film capacitor structure
The internal structure of the thin film capacitor main ways: metal foil (or on plastic foil obtained by metal processing) as an electrode plate, to the plastic as the dielectric. Through winding or multilayer technology derived. The various arrangements of the foil and the film can be derived from a variety of configurations.
The classification of the film capacitor
1, the dielectric classification;
(The medium electrode plate) arrangement taxonomy;
3, the structure of the taxonomy;
The line ends taxonomy.
The classification of a film capacitor
Depending on the dielectric film capacitors can be divided into the following three categories:
A, T type: i.e. PE T-Polyethylene terephthalate (polyethylene terephthalate (or ester))
, P-type: P P-Polyethylene (polypropylene)
3, N-type: i.e. PE N-Polyethylene naphthalate (polyethylene naphtha)
The main characteristics of the thin film capacitor
Film capacitors on the application of the main characteristics:
1, Promise sexual;
Insulation resistance is high;
3, excellent frequency characteristics (wide frequency response);
4, the dielectric loss is small.
Function of the film capacitor
DC power supply lines is mainly applied to the DC voltage control apparatus(Metal Oxide Varistor) commercial frequency ripple less, while avoiding transmitted to the AC power line control means generates high-frequency clutter, so looking into the capacitor from the AC power line or rectifier, For 50Hz frequency, it is necessary to render the low impedance; looking into the capacitor by the control device for high-frequency clutter, but also presents a low impedance; if impedance is 0, then the ripple voltage and high-frequency clutter voltage will become 0.
Therefore, the electrode area S is increased, the electrical capacity can be increased. In addition to the electric capacity, often also parasitic various impedance, in the occasion of the electrolytic capacitor, the electrode is configured to elongate metal foil wound into a cylindrical shape, in addition to the electric capacity, yet additional elongate electrodes arising inductance component. Further, the electrode leads to an external terminal used wire inductance component; while the ratio of the electrolyte constituting the electrolytic capacitor of the cathode resistance of about 100 Ω-cm, and this is one of the elements to restrict the effect of the filtering.
The capacitor of the film (film) based on the plastic film as an insulating material, the metal foil wound into a cylindrical shape or become integrated layered, in order to increase the area. However, in the occasion of the film capacitor into a cylindrical shape, even if the wound, since the electrode leads to pass through the metal flame spraying for the contact (metalcon) a after its inductance can be reduced a lot.
The efficacy of the film capacitor in parallel
A transistor down chopper (chopper), the 50kHz as switching DC power line high-frequency clutter voltage waveform. 2200μF electrolytic capacitor terminal, about there 2V of the clutter, if 2.2μF film capacitor in parallel, it will inhibit become 0.1V. If the electrical capacity of the thin film capacitor is not sufficient, the peak voltage of the clutter will be reduced, the vibration frequency is low, it will easily be seen(Metal Oxide Varistor).
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