Applications of Film Capacitors

Film capacitors have various names; plastic film capacitors, polymer film capacitors, or film dielectric capacitors.

These are electrical capacitors with an insulating plastic film as their dielectric. They are sometimes combined with paper to act as a carrier for electrodes.

Film capacitors can be made metallic with zinc or aluminum by applying either of the metals directly to the plastic film.

The bipolar nature of film capacitors makes them popular for high-frequency circuits. Again, each film provides different temperatures, making them the right choice of dielectric for the optimal solution to any circuits' needs.

Besides, film capacitors are known for their; stable capacitance, high insulation resistance, and low dissipation factor. This makes them suitable for a wide range of applications for optimum performance.

Here some applications for plastic film capacitors;

1. Used in light ballasts

A light ballast is a device used to properly start and operate the electrical conditions of fluorescent lamps.

This limits the amount of current passing through the fluorescent lamps, which would be destructive to the tubes due to a rise in the tubes' negative resistance levels.

Using an inductor will result in poor power factors when the current is shifted from the phase. More advanced light ballasts are developed to adjust circuit topology with Power Factor Correction (PFC).

In a fluorescent power system, the ballast regulates current passing to the lamps by providing sufficient voltage to start the lamps. If this system is not in place, the lamps could take too much current, overheat and probably burn out.

Again, this maintains the temperatures of the optimal electrodes to increase the life span of lamps. The ballast's output must meet the exact requirements that match the lamps' electrical specifications to achieve the rated lamp life from a fluorescent lamp system.

For example, a four-foot T8 type of lamp sets a specific voltage of either 277volts or 347 volts. Hence make sure you find a ballast compatible with your type of lamp.

Some advantages of using light ballasts are;

● They are easy to dim.

● Reduced heat.

● Instant start options.

● They produce steady light and fade over time.

2. Power film capacitors

This application is for large power ranges. Film capacitors made for power usage are similar to those made from small appliances but soften marked and specified for historical purposes.

Engineers design both AC and DC power capacitors. Altenatinating Current capacitors are used in close-tuned or low-turned filter circuits for filtering and absorbing harmonics. They are operating in reversing voltages in appliances like magnetizing equipment.

AC capacitor works well as snubbing and damping capacitors when connected in a series with a resistor. Also, it damps undesirable voltages caused by the charge carrier storage effect during switching of power semiconductors.

For high voltage testing equipment, DC capacitors are used to reduce the AC component of fluctuating DC voltages.  DC-filter capacitors are used for energy storage intermediate for DC circuits such as transistors, frequency converters for poly-phase drives, and thyristor power converters.

Some advantages of using these power film capacitors are;

● Much lower aging compared to electrolytic capacitors of similar values.

● Metallic construction has high self- healing properties.

● High rated voltages, up to the range of kV possible.

However, there some disadvantages that come with using power film capacitors;

● Possibility of flammable under overload conditions

● Large physical size compared to electrolytic capacitors.

● A limited number of types in surface-mount technology

3. Electric circuits

For electric filter purposes, film capacitors specifically, polypropylene meet class 1  criteria for their low electrical loss and linear behavior for a wide range of temperature and frequency range.

They are used for resonant circuits and oscillators in applications like loudspeakers as audion crossovers.

PP film capacitors are suitable when applications that need a high current pulse-like welding machine, time-domain reflectometer, generate high-energy light or X-ray flashes, and defibrillators.

Also, film capacitors are used as decoupling capacitors to suppress transients or noise from electronics.

PPTFE film capacitors are used in equipment withstand very high temperatures like the aerospace industry, military equipment,  burn-in- circuits, and geographical probes.

Some advantages of using film capacitors in electric circuits are;

● Electricity stability.

● Reduced cost of maintaining the electric systems

● Make electricity more reliable.

4. Damping/ Snubbers capacitors

There are used as energy-absorbing to minimize voltage spikes caused by circuit inductance when a switch opens. Snubbers improve electromagnetic compatibility (EMC) by eliminating voltage transient. Also, it suppresses the sparks of switch contacts.

Snubbers circuits are incorporate in film capacitors and consist of resistors in series. They are connected in parallel with semiconductors to damp undesirable voltage spikes.

These film capacitors are expected to be very reliable because if the snubber RC  circuitry fails, a power semiconductor will be destroyed in most cases.

Some advantages of using snubber capacitors are;

● Reduces the power dissipation  in switching networks

● Limits rate f rise for voltage and current

● Reduces EMI by damping current and voltage ringing.

5. EMI/RFI  and  Safety  suppression film capacitors

AC line filter safety capacitors are critical components in reducing or suppressing electrical noise caused by electrical equipment operation.

This protects against electrical shocks that might emanate from the electronics.

Electrical impendence decreases with increasing frequency, so the suppression capacitor helps in the interference reduction.

This prevents electric equipment and machinery, like a motor, from receiving and sending radio and electromagnetic frequency interference.

Most Radio Frequency Interference is metallic  PP film capacitors, but some made from paper are still being used. Some advantages of using these metallic PP film capacitors are;

● Easy connection and low inductance.

● High voltage per element.

● Non-polar dielectric.

● High current per capacitance.

● No leakage of poisonous or dangerous electrolyte.

● High compatibility to withstand over two times the rated average.

Conclusion

Film capacitors come in all shapes and forms to suit specific applications, from large scale appliances like in the electric grid system to small equipment like sound speakers.

The main advantage is to regulate electricity flow and safeguard electric equipment from getting destroyed from too much current flow due to increasing their lifespan.

Even in homes, film capacitors protect you from electric malfunction by keeping all electronic equipment using these capacitors from overheating and causing electric hazards.