Working Principle of BLDC Motor
The BLDC motor is mainly composed of the motor body, position sensor, electronic commutation circuit and driver. The motor body is similar in structure to a permanent magnet synchronous motor, but it has neither cage windings nor other starting devices. The stator windings are generally made into multiple phases (three-phase, four-phase, five-phase and so on). The rotor is composed of permanent magnet steel according to a certain number of pole pairs (2p=2, 4...). In a brushless DC motor, the armature winding is arranged on the stator, and the permanent magnet poles are arranged on the rotor. The position of the armature winding of each phase of the stator relative to the magnetic field of the permanent magnet of the rotor is sensed by the rotor position sensor electronically or electromagnetically. Moreover, it uses its output signal to drive the corresponding power switch transistor connected with the armature winding through an electronic conversion circuit according to a certain logic program, and commutate the current switch to the corresponding armature winding. With the rotation of the rotor, the rotor position sensor continuously sends out signals, causing the armature winding to be continuously energized in sequence, and the energization state is constantly changed. As a result, the direction of the current flowing in the coil conductor under a certain magnetic pole is always the same, and the rotor keeps running.
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As an important form of energy generation, air compressors are widely used in various industrial fields, including mechanical, metallurgy, Electronic power, medicine, packaging, chemicals, food, textile, transportation and so on.
Direct drive of air compressor refers to the motor main shaft to drive the rotor by the coupling and the gearbox speed, which is not actually a direct drive in practical sense.
Direct drive in the true sense means that the motor is directly connected with the rotor (Coaxial), which has the same speed. This situation is obviously very rare. Therefore, it is a wrong view that there is no energy loss in direct drive.
Another drive way is belt driven, which allows the rotating speed of the rotor to be changed by pulleys of different diameters.
As a relatively safe transformer in the power industry, isolation transformer has been widely used in electronic industry or industrial and mining enterprises, machine tools and mechanical equipment in general circuit control power supply, safety lighting and indicator power. Due to its excellent product performance, isolation transformer has been used in more fields and scope, and may gradually replace the ordinary transformer. What's the difference? The following is a simple analysis of the main differences between the isolation transformer and the ordinary transformer.
Although three-phase isolation transformers and single-phase isolation transformers are different types of step-up & step-down isolation transformer products, they all have very similar functions and can be used for converting voltage and current, safe isolation and voltage regulation, and play a very important role in many professional fields. However, there are significant differences between them.
People found that the air conditioner also has a little dehumidification function in the process of using the air conditioner. Nowadays, air-conditioning manufacturers have deliberately added a dehumidification mode based on the two modes of cooling and heating to increase the selling point of air-conditioning. However, consumers still have many doubts about whether to buy air conditioners or dehumidifiers. So which one is more cost-effective to buy a dehumidifier or an air conditioner with dehumidification?
Industrial camera can be divided into interlaced scanning industrial cameras and progressive scanning industrial camera according to scanning mode.
Most displays and industrial cameras adopt the interlaced scanning, but it actually looks like a smooth image in human eyes. Industrial cameras usually get odd rows of images first, for CCIR standard, industrial cameras get the even rows after 1/50 seconds, but for EIA standard, the industrial cameras get the even rows after 1/60 seconds.
The instrument transformers like current transformer and potential transformer (also called voltage transformer) are both used for measuring devices, which have a similar working principle to transformers. The current transformer can reduce the high current to low current, while the potential transformer steps down the high voltage to low voltage for measuring the circuit or in the power distribution. They both separate the measurement circuit from the high-voltage grid to protect safety of the personnel.
Relays and transistors have a similar basic function, that is, both play roles of electronic switches. However, relays and transistors are very different from each other. Now let’s take a quick peek at the differences between relays and transistors.
What is the frequency converter? Frequency converter outputs the AC power to pure sine wave after the transformation of AC→DC→AC, the output frequency and voltage can be adjusted within a certain range. It is different from the variable frequency drive (VFD) used for motor speed regulation, and also different from the common AC regulated power supply. An ideal AC power supply is characterized by stable frequency, stable voltage, zero internal resistance and pure sinusoidal voltage waveform (without distortion). Frequency converter is quite close to the ideal AC power supply, so more and more countries use it as standard power supply to provide the best power supply environment for electrical appliances, so as to assess the technical performance of electrical appliances.
Image sensor is an important part of the industrial camera. According to difference of the original, it can be divided into CCD and CMOS sensors. In the last 25 years of the last century, CCD technology has been leading the trend of the imaging sensor. It is a high-resolution and high-quality image sensor which can be integrated on a very small chip. However, in recent years, with the rapid development of the semiconductor manufacturing technology, the size of the integrated transistor is becoming smaller and smaller, and the performance is much better. CMOS image sensor obtains rapid development in the recent years, and it seems CMOS image sensor has overtaken CCD image sensor. CMOS provides the performance on a par with CCD in the mid-end and low-end applications, and has a significant advantage in price. With the development of technology, CMOS will also occupy a space in the high-end application field. This paper makes a detailed explanation to the difference between CCD and CMOS image sensors in the industrial camera.
Have you ever though why your motor has a shorter service life than that of others? Let us tell you, your motor may need a soft starter. Generally, the motor shall adopt a soft starter as soon as its power exceeds 20hp (15kW), otherwise it will affect the use and operation of other equipment in power grid and damage the motor. Why should the soft start controller be used? What are the benefits of using motor soft starter?
As the common part of the electrical device, both the surge protection device and lightning arrester have the function of preventing from over-voltage, especially preventing from the lightning over-voltage. However, the two have great differences.
- Different voltage level from the perspective of application field
- Different protecting objects
- Different insulation level or withstand voltage level
- Different installation position
Current transformer is mainly used to measure the current of busbar and primary side with iron core coils in AC occasion. It can detect the DC current, can be single core or dual cores, generally, it's equipped with auxiliary DC winding. Such a structure is simple, reliable and slow. Technology and design of the current transformer are complex, its common precision is 5%, it's difficult to reach 0.5% because phase position and compensation are difficult. A current transformer is an electrical component that turns large current into small current, it doesn't change the current frequency but only the size. Its secondary side current is 5A, that means the output rated current is 5A. It's mainly used for electrical control, measurement, protection and signal.
The gas solenoid valve is used for various ambient temperature, high temperature, negative pressure, low pressure and high pressure applications. The applicable fluid is air, nitrogen, oxygen, hydrogen, helium, carbon dioxide gas, argon gas, methane and other gas pipelines. Generally, solenoid valve for gas is mainly used in wide applications such as medical apparatus and instruments, rubber plastic machinery, clothing equipment, drying equipment and pharmacy industry, cooling industry, HVAC industry, electroplating coating industry, food and beverage industry and vacuum equipment industry.
As everyone knows, direct starting of water pump would cause the water hammer effect. Namely when the water pump starts and stops, water impacts the pipe and cause a serious water hammer. When the power is off suddenly or the valve turns off quickly, a water impact wave generates due to inertia of pressure flow, which is like the knock of a hammer, so it’s called water hammer. Sometimes the force generated from water impact wave may be great and damage valve or pump, therefore, to avoid the negative effect of water hammer effect, the pump’s rotation speed should increase to the rated speed slowly when it’s started. Two methods are applicable, one is the variable frequency starting, another is the soft starting.
Safety relay has special color, generally yellow. Current safety relay acts reliably and flexibly, it's mainly used to control the power supply circuit. When an emergency occurs, the circuit controlled by the safety relay is disconnected by pressing the emergency stop switch, thus ensuring safety.
Infrared temperature measurement technology plays an important role in production, product quality control and monitoring, on-line fault diagnosis and safety protection, as well as energy saving. Compared with the contact-type temperature measurement method, infrared temperature measurement has the advantages of fast response time, non-contact, safe use and long service life. Non-contact infrared thermometer involves three major series of portable, on-line and scanning thermometer, with various accessories and computer software. Moreover, each series has different types and specifications. Among these thermometers with various specifications, it is very important for users to choose a correct type of infrared thermometer.
Iron core of the AC contactor is usually laminated by silicon steel sheet, so as to reduce the eddy current and hysteresis loss generated by alternating magnetic field in iron core, avoid the iron core overheating. However, iron core in the DC contactor's coil would not generate eddy current and there is no heating problem in DC core, so the iron core can be made of a complete cast steel or cast iron. Coil of DC circuit has no inductance, so the coil has more turns, thus leading to large resistance and copper loss. In order to keep a good heat dissipation for the coil, the coil is generally made into a thin and cylindrical shape. Coil of AC contactor has less turns and small resistance, but the coil also gives heat, so the coil is generally made into a fat and short cylindrical shape. Meanwhile, a clearance is left to facilitate heat dissipation while avoiding the coils from being burned out. In order to eliminate vibration and noise generated by electromagnet, a short circuit ring is embedded on the surface of static iron core of the AC contactor, while the DC contactor doesn't need a short circuit ring.
Industrial thermocouple and RTD protective casing are almost the same. Some temperature measuring elements are small in size, such as the armored type, and they also have similar shape. So, how to identify whether it is RTD or thermocouple without nameplate or unknowing the type? The following methods are listed to figure out the RTD and thermocouple for your reference.
The common line reactors in electrical power system include series reactors and paralleling reactors. Series reactors are mainly used to limit short-circuit current or ultraharmonics in filter by connecting with capacitor in series or in parallel. The line reactors in power grid of 220kV, 110kV, 35kV and 10kV are used to absorb the idle work of charging capacity of cable line. Operating voltage can be adjusted by adjusting the number of line reactors in parallel. Ultra-high voltage paralleling reactor can improve the operation conditions relating to reactive power of electrical power system including:
