Technical post: Use icons to tell you the difference between constant speed and frequency conversion!
The fixed speed air conditioner means that the speed of the internal compressor motor is constant and the temperature is adjusted by switching the compressor on and off.
Inverter air conditioner refers to the use of the principle of frequency conversion, the use of variable AC power obtained from the secondary inverter to adjust the speed of the compressor, thereby changing the refrigerant circulation in the pipeline and controlling the output capacity of the air conditioner.
AC frequency conversion means that the rotor rotates through the interaction of the magnetic field between the stator and the rotor. The AC frequency conversion air conditioner has the characteristics of rapid cooling and heating and accurate temperature control.
DC frequency conversion refers to the use of a DC frequency conversion compressor. The rotating magnetic field generated by the compressor stator directly interacts with the permanent magnetic field of the rotor to realize the operation of the compressor. The efficiency of the DC inverter compressor is 10% to 30% higher than that of the AC inverter compressor.
The difference between DC inverter air conditioner and traditional fixed frequency air conditioner
Inverter air conditioner refers to the use of the principle of frequency conversion, using the variable AC power obtained from the secondary inverter to adjust the speed of the compressor, thereby changing the refrigerant circulation in the pipeline and controlling the output capacity of the air conditioner.
The fixed speed air conditioner means that the speed of the internal compressor motor is constant and the temperature is adjusted by switching the compressor on and off.
Inverter air conditioner: Inverter air conditioner is suitable for a wide operating voltage range; low starting current; high power operation, quickly reaching the set temperature, low power maintenance, and room temperature balance, so the cooling and heating are rapid, power saving, and room temperature fluctuations are small.
Fixed-speed air conditioner: The fixed-frequency air conditioner operates at a fixed power and maintains the indoor temperature by frequently turning on and off the machine. Therefore, the cooling and heating speed is slow, which has a large impact on the home power grid and large room temperature fluctuations.
The difference between DC inverter air conditioner and AC inverter air conditioner
The main difference between AC inverter products and DC inverter products is the compressor and control system:
1. The difference between compressors
The compressor motor used in DC inverter air conditioners and AC inverter air conditioners, in principle, is that the stator generates a continuously rotating circular rotating magnetic field, and the magnetic field force interaction between the stator and the rotor generates a torque to continuously drive the rotor to rotate.
①AC frequency conversion:
The compressor uses an AC motor drive principle: an AC inverter compressor is used to rotate the rotor through the interaction of the magnetic field between the stator and the rotor. But its special design makes it possible to change the speed of the motor in a larger range by changing the frequency and voltage of the power supply.
Features: Compared with fixed frequency air conditioners, AC inverter air conditioners have the characteristics of fast cooling and heating and precise temperature control. However, the operation of the AC variable frequency compressor is realized by the interaction of the magnetic lines of force formed by the current passing through the stator winding and the induced current on the rotor winding. Therefore, the rotor winding has current flowing through it, resulting in power loss. Its cost is much lower than DC inverter air conditioner.‘
②DC frequency conversion:
The compressor adopts the driving principle of DC motor: adopting DC inverter compressor, the rotating magnetic field generated by the compressor stator and the permanent magnetic field of the rotor directly act to realize the operation of the compressor. Since the rotor is a permanent magnet, there are no coils/windings, no external power supply is needed, and no power loss is generated, which has high efficiency and energy saving.
Features: high efficiency and low noise. The efficiency of the DC inverter compressor is 10% to 30% higher than that of the AC inverter compressor, and the noise is 5 to 10 decibels lower. AC frequency conversion and DC frequency conversion are two generations of products.
2. Differences in control systems
①AC frequency conversion:
The AC inverter compressor adopts asynchronous control, (220V/50Hz mains power is rectified and filtered to obtain a DC power of about 310V. After this DC power is inverted, the inverter power supply used to control the operation of the compressor can be obtained.
Pulse width modulation (PWM): In each half cycle of the output voltage, the waveform of the output voltage is divided into several pulse waves, because the average value of the output voltage and the duty cycle of the pulse (the width of the pulse divided by the period of the pulse is called Duty ratio) is proportional, so while adjusting the frequency, the pulse voltage amplitude is not changed, but the duty ratio of the pulse is changed, which can achieve the effect of frequency conversion and voltage transformation. This method is called PWM (PuleWidth Modulation) modulation. PWM modulation can directly change the voltage and frequency at the same time in the inverter), and the control circuit is relatively simple.
②DC frequency conversion:
The DC inverter compressor belongs to synchronous control, which detects the position of the compressor rotor at all times, and performs real-time adjustment according to the position of the compressor rotor to control the compressor frequency.
The compressor adopts brushless DC motor (120°) or permanent magnet synchronous motor (180°), and the frequency conversion is DC frequency conversion. If an AC motor is used, the frequency conversion is AC frequency conversion; in addition, full DC frequency conversion means that the compressor, indoor and outdoor fans all use DC brushless motors, and some DC means that only the compressor uses DC brushless motors.
Working diagram of scroll compressor
The working principle of digital scroll compressor:
Digital scroll compressor is realized by the time ratio of load and unload in a time period. The compressor capacity is changed by the periodic engagement and expansion of the scroll. When the external solenoid valve is closed, the compressor output capacity is in a load state. When the external solenoid valve is opened, the compressor has no capacity output and is in an unloaded state. Example: If the set time period is 20 seconds and the load is 10 seconds, which accounts for 50% of the 20 second period, 50% will be output.
Digital scroll compressor
Main structure of digital scroll compressor
The role of PMW valve in digital scroll compressor
The role of PMW valve in digital scroll compressor
Working principle of inverter compressor
The compressor capacity is changed by the speed of the compressor motor. When the indoor load requirements are high, the compressor motor frequency will increase, resulting in faster motor speed and higher capacity. When the indoor load requirement decreases, the frequency of the compressor decreases, thereby reducing the capacity.
Comparison of Digital Scroll and Inverter Scroll Compressor
Digital scroll technology capacity adjustment fast
The output of the digital scroll technology is between 10% and 100%. The compressor output can be changed by changing the ratio of the loading time, so as to achieve continuous capacity output with no level output;
The frequency range of inverter technology is between 52 Hz and 210 Hz. The compressor operates at a limited capacity level (for example: 21 levels), so the capacity output is intermittent. Moreover, when the indoor load suddenly changes from small to large, the frequency of the compressor needs to increase through the intermediate transition section. This means that if the indoor load requirements change, the compressor will have to respond to the new load for a period of time and cannot respond immediately.
Relatively speaking, digital scroll technology is more energy efficient than COP
The digital scroll technology has no frequency conversion loss and no refrigerant hot gas bypass, so it has excellent COP performance within the load range of 10% to 100%. The energy loss at no load is very low (only 10%), which also makes the COP value of the Digital Scroll even higher under partial load.
Frequency conversion technology The frequency conversion system loss accounts for about 15% of the power consumption, which reduces the COP value of the system. When the total capacity requirement of the indoor unit is low (such as 10%, 20% or 30%), the inverter system must use refrigerant hot gas bypass for capacity adjustment, because the minimum capacity output of the inverter compressor is about 40%. When the total indoor capacity requirement is low, energy will be lost due to the bypass of the hot air of the refrigerant, and the COP value of the system will decrease. Because the frequency of the motor is constantly changing, it is difficult to determine the energy efficiency ratio of the frequency conversion system. In order to measure stable operating conditions, an external device must be used to ensure that the compressor frequency is fixed. In this case, the energy measurement does not include the loss of the inverter. In order to obtain the true performance parameters, a typical frequency conversion system loss of 15% must be included, otherwise the data will show an untrue higher COP.
Energy loss:
1. The frequency converter loses 10%;
2. The efficiency loss of the motor after the rotation speed is changed can reach 5-10%;
3. The frequency conversion system needs to be bypassed when the load is low.
Digital scroll technology has low electromagnetic interference
The digital scroll compressor drive only needs simple load and unload control, does not need to change the frequency of the power distribution of the power grid, basically does not generate interference electromagnetic waves, and meets the EMC electromagnetic compatibility requirements; the inverter compressor generates high-order harmonics and is not suitable for use Precision places such as communication rooms do not meet EMC requirements.
Digital scroll system diagram
