Permanent magnet variable frequency air compressors have become a hot topic and highlight in the industry due to their energy-saving and high-efficiency characteristics. The original high-energy-consuming air compressors on the market are gradually being replaced or replaced by permanent magnet variable frequency air compressors, which can directly bring users 20%-40% cost savings.
With the development of science and technology, air compressors, as an important power equipment, are widely used in many industrial fields such as machinery, metallurgy, building materials, electronics, power, chemicals, food, and textiles. However, air compressors are high-energy-consuming equipment, accounting for more than 30% of the electricity consumption in some industries, hence the nickname "electricity guzzler".
In recent years, permanent magnet variable frequency air compressors have become a hot topic and highlight in the industry due to their energy-saving and high-efficiency characteristics. The original "energy hogs" in the market, namely air compressors with high energy consumption, are gradually being replaced or replaced by permanent magnet variable frequency air compressors, which can directly bring users 20%-40% cost savings.
Why are permanent magnet variable frequency air compressors so popular in the market? The current booming use of permanent magnet variable frequency air compressors in industry inevitably brings to mind power frequency driven air compressors. So, what are the differences between the two?
I. Stable air pressure
1. Because the variable frequency screw air compressor utilizes the stepless speed regulation feature of the frequency converter, it can start smoothly through the controller or the PID regulator inside the frequency converter; and it can quickly adjust and respond in situations where the air consumption fluctuates greatly.
2. Compared with the upper and lower limit switch control of power frequency operation, the air pressure stability is improved exponentially.
II. Shock-free startup
1. Since the frequency converter itself includes the function of a soft starter, the maximum starting current is within 1.2 times the rated current. Compared with the power frequency starting, which is generally more than 6 times the rated current, the starting impact is very small.
2. This impact is not only on the power grid, but also on the entire mechanical system, and is greatly reduced.
III. Variable Flow Control
1. A fixed-frequency driven air compressor can only operate at one discharge capacity, while a variable-frequency air compressor can operate at a wider discharge capacity range. The frequency converter adjusts the motor speed in real time according to the actual air consumption to control the discharge capacity.
2. When air consumption is low, the air compressor can be put into automatic sleep mode, which greatly reduces energy loss.
3. Optimized control strategies can further improve energy-saving performance.
IV. AC power supply has better voltage adaptability.
1. Due to the overmodulation technology used in the frequency converter, it can still output sufficient torque to drive the motor when the AC power supply voltage is slightly low; and it will not cause the voltage output to the motor to be too high when the voltage is slightly high.
2. In situations where self-generated electricity is generated, frequency converters demonstrate their advantages even more.
3. Based on the characteristics of the motor's voltage (VF) (variable frequency air compressors operate below the rated voltage in energy-saving mode), the effect is significant in sites with low grid voltage.
5. Low noise
1. Most operating conditions of the frequency converter system are below the rated speed, which reduces the mechanical noise and wear of the main unit, and extends maintenance and service life.
2. If the fan also uses frequency conversion drive, the noise of the air compressor during operation can be significantly reduced.
The difference between variable frequency and fixed frequency is obvious. The energy-saving and efficiency advantages of permanent magnet variable frequency air compressors are essential for winning the market.
While variable frequency air compressors are advantageous, their inherent operating principle means users still face certain risks when using permanent magnet variable frequency air compressors. The greatest risk is demagnetization due to high temperatures. As is well known, the key component of a permanent magnet motor is the magnet, which is extremely vulnerable to high temperatures. Permanent magnet variable frequency air compressors will gradually demagnetize under prolonged high temperatures; the higher the temperature, the greater the risk of demagnetization.
There are many cases of permanent magnet air compressors failing due to demagnetization of the magnets in various industries. Once a permanent magnet air compressor demagnetizes, the speed is astonishing. After partial demagnetization, the motor current will continue to increase, energy consumption will rise, and the user's electricity costs will increase. At the same time, there is a possibility that the motor will "break down" at any time, which may even lead to the scrapping of finished products in the product line.
What factors can trigger the risk of demagnetization?
1. High Temperature Resistance Rating of Permanent Magnet Motors: The magnetic material of permanent magnet motors uses neodymium iron boron (NdFeB) magnetic material. As the latest development in rare earth permanent magnet materials, it is known as the "King of Magnets" due to its excellent magnetic properties. Its main components include: 29%-32.5% neodymium (rare earth metal), 63.95-68.65% iron (metallic element), and 1.1-1.2% boron (non-metallic element). Another important performance indicator for permanent magnet motors is their high temperature resistance rating. Exceeding this rating, the magnetic flux density drops sharply. High temperature resistance ratings are divided into: N series (resistant to temperatures above 80 degrees Celsius); H series (resistant to temperatures above 120 degrees Celsius); and SH series (resistant to temperatures above 150 degrees Celsius).
2. Motor Protection Rating: Protection ratings are divided into IP23 and IP54. IP23 motors, due to temperature constraints, can only be designed as open-type motors. Air compressors are often used in harsh environments where dust, moisture, salt spray, and other corrosive gases shorten their lifespan. In particular, metal-containing dust entering the motor will severely affect the magnetic wire distribution, causing a decrease in efficiency. The higher protection rating of IP54 motors avoids these risks.
3. Motor heat dissipation: Due to the special material of permanent magnet motors, how to ensure heat dissipation and cooling is a key point. Currently, permanent magnet variable frequency air compressors on the market mainly use three motor cooling methods: air cooling, water cooling, and oil cooling.
(1) Air cooling: low cost, worst heat dissipation, high maintenance cost, and large size.
(2) Water cooling: good heat dissipation, highest cost (requires water tank, water pump or water circulation system), prone to corrosion and rust, and has the highest requirements for sealing.
(3) Oil cooling: small size, good heat dissipation, low cost, and can utilize the air compressor lubricating oil circulation system.
In recent years, with the slowdown of national economic growth and the adjustment and transformation of industrial development, the growth rate of market demand for air compressors has gradually slowed down, intensifying competition among air compressor companies. At the same time, under the national policy of energy conservation and emission reduction, and the need for user companies to reduce energy consumption and cut costs, the emergence of permanent magnet variable frequency air compressors has provided a lifeline for major air compressor manufacturers struggling in fierce competition, prompting them to rush into the variable frequency air compressor trend. More and more variable frequency air compressor brands have emerged in the market, some using foreign brands and adopting foreign names, others claiming joint ventures and foreign technology, all hoping to capitalize on the opportunity. The industry has grown rapidly due to increased participation, but behind this seemingly prosperous scene lie many unstable factors.
The development of variable frequency air compressors has been rapid in recent years, but the growing pains have been constant. News reports of substandard air compressors and even explosions have raised concerns about product quality outside the industry. This not only affects the healthy development of the industry but also seriously impacts the interests of customers.
Therefore, while we understand and promote the advantages of permanent magnet variable frequency air compressors, we must also understand and demonstrate their shortcomings and disadvantages, so as to alert manufacturers and warn users!
