Contact Us+8613505873345

Search

Some discussion on energy saving of frequency converter

Jan 19, 2021

Some discussion on energy saving of frequency converter

As an advanced energy-saving technology, inverter technology has been popularized and applied for many years. Inverters are also widely used in all aspects of industry and civil use. But does it really save energy after using the inverter? People often feel different!


    Opinion 1: Some people say that the inverter air conditioner is installed in my home, but it does not save electricity or even consumes more electricity. Therefore, the inverter does not save energy.


    Viewpoint 2: Some people also say that the water pump of our plant's chiller has undergone a frequency conversion transformation, and the energy saving effect is very obvious. So the inverter can save energy.


    Point of view 3: The frequency converter speed regulation seems to save electricity, but because the frequency converter is not efficient, and the efficiency of the motor will be reduced at low speeds, the frequency converter is not energy-saving. Moreover, the cost of configuring the inverter is relatively high. Even if it can save a little electricity, it is not economically cost-effective overall.


    Friends, have you also had the above views?


    Why does the same technology produce different effects? Let's analyze it in detail:


    First, take a look at the basic principles of the inverter:


    Inverters are usually used in fans, pumps, compressors and other equipment, and the medium is fluid. According to the principle of fluid mechanics, when an induction motor drives a load such as a water pump, the flow Q is proportional to the motor speed n, and the pressure H is proportional to the square of the motor speed n. The actual power of the motor is proportional to the flow and pressure as P∝QxH, which is power It is proportional to the 3rd power of the speed. For example, when the motor speed drops to 0.8 times the rated speed, the power consumed by the motor will drop to 0.83=0.512 times the rated power. It can be seen that the use of frequency conversion technology can greatly save energy.


    Based on this theory, let's turn to the several viewpoints mentioned earlier:


    Opinion 1: Some people say that the inverter air conditioner is installed in my home, but it does not save electricity or even consumes more electricity. Therefore, the inverter does not save energy.


    Analysis: According to the above analysis, the premise of the inverter energy saving is that the load is small and the motor speed slows down. The inverter air conditioner at home does not save energy because the load is not reduced at all, and the compressor always runs at a higher speed. For example, under the same climatic conditions, if a 3-hp air conditioner is installed in a room of 10 square meters, the air conditioner will not operate at full capacity, and the inverter air conditioner will definitely save energy; if a room of 100 square meters is also installed with a 3-hp inverter air conditioner, it will definitely not save energy. , Because the air conditioner always runs at full capacity. It can only be said that when the air conditioner manufacturer claims that the inverter air conditioner is energy-saving, it is not clear under what circumstances. Do you feel fooled?


    Viewpoint 2: Some people also say that the water pump of our plant's chiller has undergone a frequency conversion transformation, and the energy saving effect is very obvious. So the inverter can save energy.


    Analysis: Usually in industrial design, loads such as fans and pumps have a relatively large margin, and in most cases, the operating load is low. Under this premise, the frequency conversion energy-saving technology has a lot of energy-saving space. However, the transformation of the frequency converter should be based on the specific project operation conditions and make a technical and economic comparison. Simply put, how long will it take for the initial investment of new construction or renovation to reap the rewards through inverter energy-saving technology.


    Point of view 3: The frequency converter speed regulation seems to save electricity, but because the frequency converter is not efficient, and the efficiency of the motor will be reduced at low speeds, the frequency converter is not energy-saving. Moreover, the cost of configuring a frequency converter is relatively high. Even if it can save a little electricity, it is not economically cost-effective overall.


    Analysis: This point of view considers more comprehensively, considering the efficiency issue from the perspective of energy saving of the entire system. However, what I want to say is that the efficiency of the inverter may be higher than expected. The current mainstream inverter technology can usually reach more than 0.9. When the motor speeds down, the efficiency drops, but the energy consumption is three times the speed. The proportion of the party has decreased. It can be said that when considering the efficiency of inverters and motors, inverter technology is still energy-saving. Of course, the premise is that there is a premise to reduce load operation.


    As for whether the overall economy is cost-effective, only technical and economic comparisons can be made for specific projects.


    Thinking: Frequency converter energy-saving technology is a relatively mature technology, but whether all loads and all operating conditions are suitable for configuration of frequency converters, the answer is no. We still have to make technical and economic comparisons based on specific conditions. In fact, the inverter has a variety of functions, such as speed regulation, soft start, voltage stabilization, etc. Energy saving is only a function brought by the speed regulation, so don't "forget the root".