Air Conditioner Capacitors

Air conditioner capacitors are commonly used in the electric circuit of an air conditioning system. They are used in various circuits for different purposes. We will discuss in greater details where these components are used. However, it is good to go to the fundamentals of a capacitor.

A capacitor is used to store energy in the form of electrical charge. In simple terms, it basically consists of two conductor plates with an insulating material in between them. The insulating material is also called a dielectric and can be made of paper, special non-conductive material or simply the air. They are used in both AC and DC circuits.

The capacitance value is dependence on:

  • Dielectric material (The higher the dielectric K, the higher the capacitance.)
  • Area of the plates (The bigger the area, the higher the capacitance.)
  • Separation distance of the plates (The closer the plates are, the higher the capacitance.)
  • Number of plates (The more the number of plates used to make the capacitor, the higher the capacitance.)

The symbols used to represent capacitors are as shown below.

The unit of measurement is Farad(F) and the common values are uF(microfarad) which is 0.000001 Farad, mF(milifarad), nF(nanofarad) and pF(picofarad). 

Voltage Rating

The voltage rating of a capacitor determines the maximum voltage that should be applied during operation. Take note also of the usable temperature range that can be used. If you are replacing a capacitor, make sure that the capacitance is the same and the voltage rating does not go below the old capacitor that is to be replaced. Also ensure that the type of capacitor used is similar.

Types of Air Conditioner Capacitors

Electrolytic Capacitor 

This capacitor has polarity and have leads that are marked with + or - signs. It is usually used to smooth-en the DC voltage after the voltage has being rectified by the diodes. They helped to reduce the ripples of the DC supply. The bigger the capacitance of the capacitor used, the less the ripple will be. You will find this application in simple linear power supply together with a step down transformer.

Ceramic Capacitors 

Ceramic caps. are used as bypass capacitors to bypass the high frequency content of a circuit. They could be placed parallel to the DC power intake of integrated circuits to bypass certain high frequencies noise in the circuit that may have adverse effect on the sensitive circuitry.

As more tranformerless power supply is becoming common today due to its better efficiency and smaller space, you will see many surface mount capacitors being used in multilayer printed circuit boards.

Safety Capacitors

Safety caps. are commonly used in inverter control circuity of an air conditioner. They can be classified into X or Y types and are used in the live parts of the circuit. Hence, always be careful when dealing with this capacitors as some charge on them may cause shock even when power supply has been cut off.

Good design should have bleeding resistors to remove the charge from the device after the air conditioner has been switched off. Ensure proper certification marks such as VDE, UL and CE markings are presence on the bodies of the capacitors before using them.

These capacitors together with inductor coils are used to reduce the harmonics that are generated from the rapid switching of the AC power supply by the insulated gate bipolar transistors (IGBT).

Start & Run  Air Conditioner Capacitors 

These capacitors are used in single phase electric motors. START cap. is used to shift the phase difference between START windings and RUN windings of a capacitor-start motor. This difference caused a starting torque to be generated that is able to start the motor with full load connected to it. 

The RUN cap. is used to further shift the phase difference between the two windings causing even higher starting torque to be generated. There are markings on the single phase compressor to identify the connections in the motor. The labels are R(connected to RUN winding), S(connected to START winding) and C(common of the two windings).

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