Energy saving analysis of EC fans compared to AC fans
This post will analyze the differences between EC fans and AC fans from the perspective of their actual manufacturing solutions, operating principles, dynamometer data of related motors, actual air volume test data of fans, actual application scenarios of AC axial fans and EC axial fans, and industry development trends.
Actual manufacturing solutions for AC motors
Stator Winding Squirrel-Cage Rotor Stator-Rotor Assembly Schematic
From the actual pictures, we can see that the AC motor's cross-slot winding scheme makes part of the enameled wire protrude beyond the core.
The main process of the AC motor's operating principle is as follows
1. The stator winding is connected to an alternating current, and a rotating and changing magnetic field is generated in the winding.
2. The stator's rotating and changing magnetic flux lines pass through the squirrel cage rotor. According to the principle of electromagnetic induction, a rotating and changing induced magnetic field will be induced on the rotor, and the rotor magnetic field "follows" the changes in the stator magnetic field.
3. The two magnetic fields interact with each other to drive the rotor to rotate.
The actual manufacturing plan of the EC motor
Stator Winding Permanent Magnet Rotor Stator and Rotor Assembly Diagram
From the pictures of the real object, it can be seen that EC motors mostly use centralized windings, which are similar to the single-tooth winding of the coil around the stator, and the enameled wire has a shorter cross-wire distance. The enameled wire exceeds the core plane relatively less.
Operating principle of EC motor
The operating principle of EC motor can be simplified into the following three steps:
1. The input AC power is rectified and converted into DC power by the controller, and the DC power is then converted into AC power of the required frequency through inversion, and then input to the motor winding through the enameled wire head connected to the electric control board. The controller generates a rotating magnetic field by connecting the windings in sequence.
2. The rotating magnetic field interacts with the magnetic field of the permanent magnet rotor to drive the motor to rotate.
3. The controller can accurately determine the position of the rotor magnetic field by monitoring the sensors, current and back electromotive force and other signals, and then conduct the corresponding winding to form a driving magnetic field.
Energy-saving analysis of EC motors in principle and application compared with AC motors
From the above analysis, it can be seen that AC motors establish an effective magnetic field through electromagnetic induction, so part of the electrical energy is used to establish the magnetic field, and the efficiency of converting kinetic energy is reduced. EC motors use permanent magnets, so there is no need for electrical energy to establish the rotor magnetic field, so there is no energy loss.
Secondly, there are differences in the winding and magnetic field effects. In the cross-slot winding process of AC motors, a large part of the enameled wire will exceed the core, which will cause leakage and heat, thereby reducing the efficiency of the motor's conversion into kinetic energy. The winding method of EC motors can reduce this loss.
Because of the induction design principle of AC motors, the rotor and stator have a fixed slip design. When the motor exceeds the designed load, the actual slip of the motor will deviate from the designed slip, thereby narrowing the overall high-efficiency range. The permanent magnet design and drive control design of EC motors will effectively avoid this situation. In order to reduce this defect of AC motors, inverters are often used in actual applications to adjust the speed of AC motors. Variable frequency speed regulation mainly includes three processes: rectification, inversion and control. In these three processes, the conversion efficiency varies depending on the operating point, roughly ranging from 85% to 96%. The main energy loss is in the rectification and inversion links, accounting for about 90% of the total loss. The actual test value of the controller efficiency of EC motors is mostly above 97%. In general, AC motors with inverters can improve the operating efficiency of AC motors to a certain extent, but there is still some gap compared to EC.
The following is the dynamometer curve of a certain AC motor and an EC motor of the same power and speed range.
From the curve, we can draw a conclusion: EC motors are more efficient and have a wider range of high efficiency.
Energy saving analysis of test data of AC fans with inverters and EC fans:
Through the analysis of the data, it can be seen that at the typical operating point of 100Pa for large axial flow fans, the static pressure efficiency of the EC solution is 3.3% higher than that of the AC plus inverter solution.
