In recent years, DC air conditioners have become increasingly popular due to their many advantages over conventional air conditioners. Since the compressor consumes the most power of any air conditioning system, changes in compressor technology have made it possible to deploy better and more efficient air conditioners or heat pumps.
AC Induction Motors
In a three-phase AC induction motor, the windings of the motor stator are designed to produce a rotating magnetic field when a three-phase AC voltage is applied to the windings.
The rotor usually has a winding embedded in an iron laminate. When power is applied to the windings, a magnetic field is generated in the rotor, causing it to react with the magnetic field in the stator.
The rotating magnetic field of the stator pulls the rotor, which tries to keep up with the rotating field. The lag or slip is about a few percent. This design is one of the traditional ways to drive a three-phase motor in a compressor.
DC Brushless Motors
In a DC brushless motor used in a DC inverter air conditioner or heat pump, the motor rotor consists of permanent magnets and the stator has windings on it.
Compared to typical DC motors, there are no brushes and commutators, thus eliminating problems such as sparking, brush life, brush residue and electrical noise. The motor's windings are connected to a power electronic control that determines the motor's speed through the use of a microcontroller.
Various protection and monitoring circuits are built into the electronic control to ensure efficiency and reliability. Due to its better reliability and energy efficiency, this type of motor is being used in more designs.
As a result, the main advantages of DC brushless motor compressors are quiet operation, compactness, longer life, energy efficiency and better capacity control, resulting in a more comfortable environment for the people using the equipment. Its use is no longer limited to air conditioning equipment, but can also be used in refrigerators, washing machines, pumps and fans.
DLCP24-18Y3A DC ELECTRIC AIR COMPRESSOR
DC Inverter Control Circuit
The electronic control is the most complex part of the DC inverter system, thus making it one of the most expensive parts of the air conditioner, the other part being the compressor.
The control circuit of a DC compressor consists of the following.
Part 1, the DC converter
The DC converter uses four diodes connected like a bridge to convert the input power from AC to DC. Inductors and capacitors are connected before the converter to reduce the electrical noise introduced into the power supply due to the switching of the transistors.
Part 2, PFC or Power Factor Correction
Being an active power converter means that the power factor correction of this design is able to correct the power factor of the device to over 98% compared to other LC (inductor and capacitor) filter based solutions.
Part 3, IGBT Transistor Inverter
This section generates the 3-phase voltage supply for the DC compressor motor. The compressor's brushless DC motor will receive a voltage close to the 3-phase sinusoidal voltage that turns the motor on. The speed of the motor can be controlled from low to high by changing the power supplied to the motor through the switching of the transistors. When immediate cooling or heating is required, the motor will turn at the highest speed. When the room temperature stabilizes, the motor will rotate at a lower speed.