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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:

The functions of input line reactor
It can restrain harmonic current, improve power coefficient, weaken surge voltage in input circuit, the impact of current on VFD, the influences of power voltage, limit current surge caused by grid voltage change and switching surge, spike pulse or voltage defects in phase change of rectifying circuit, effectively protect VFD and improve power coefficient. Input line reactor not only can stop the disturbance from power grid but reduce the pollution of power grid by harmonic current produced by rectifying unit.

The calibration of load cell and digital display controller is mainly to confirm the weighing signal of zero point and full range of the load cell. That is to say, telling the digital display controller what are zero weight signal and full range weight signal received from the load cell. In this way, the digital display controller will display the value according to the detected weight, or export the matching weight signal to the PLC/DCS control system.

Contact system maintenance

• Check whether the position of the movable and static contact points is aligned, whether the three-phase is closed at the same time; Adjust the contact spring in case of any problem.
• Check the wear degree of contact points, the wearing depth shall not be more than 1mm. In case of contact burning or welding falling, please replace timely; Slight burning will not affect the application. The sand paper can not be used to clean the contact, a shaping file is suitable.
• The resistance shall not be less than 10MΩ when measuring the interphase insulation resistance;
• Check whether the auxiliary contact acts flexibly, the contact travel should comply with the specified value. Check whether the contact is loosening, maintain or replace timely in case of any problem.

Gas flow sensor is mainly composed of a housing, a front guide frame, an impeller, a rear guide frame, a tightening ring and a magnetoelectric induction transducer with an amplifier. The new generation of high precision and high reliability gas flow sensor is designed in accordance with the advanced technology at home and abroad, and is independently developed based on the theories of gas dynamics, fluid mechanics and electromagnetics. It has excellent performance for low pressure and high pressure measurement, multiple signal output and low sensitivity to fluid disturbance, and has been widely used in the measurement of natural gas, coal gas, liquefied petroleum gas and light hydrocarbon gas.

Helical slit flexible coupling
Helical slit flexible couplings are usually called as integrated slit cutting coupling or flexible coupling, they often have good performance and cost economy, and are regarded as preferred products in many applications.
The integrated design of a complete aluminum alloy bar makes it to have advantages of zero backlash drive moment and no maintenance. The helical slit flexible couplings can be broadly divided into two basic series: single head helix slit and multi head helix slit. It has large flexibility but low additional bearing load. Such a slit design is particularly suitable for handling the angular deviation and axial deviation, but not suitable for parallel displacement deviation, because the single head helix slit would produce multiple directional bending when handling parallel deviation, which may result in the excessive stress concentration and earlier damage of the parts.
Multi head helix slit coupling reduces the slit length without losing the ability to rectify deviation, the multi head helix slits are intertwined to enhance the torsional rigidity of the coupling, thus ensuring that the coupling can still withstand considerable torque when it has great rectifying capability. This performance makes it suitable for light load applications, such as the connection between the servo motor and the screw. However, such a design also has its shortcomings. The additional bearing load will increase as the size increases. But in most cases, as the installation error is smaller, the bending moment is also very small, thus ensuring low additional bearing load.

Humidity sensor is widely applied in many fields, particularly in the fields that record the temperature and humidity changes in real time. The temperature and humidity sensor can scientifically and effectively manage, analyze and summarize the recorded contents.

Application in the management of museum cultural relics and archives
It's another area for the application of temperature and humidity sensors. The archive papers can be kept for a longer time at a suitable temperature and humidity condition, once the temperature and humidity condition is changed, the paper will be crisp, important materials will also be lost. So it’s necessary to record the temperature and humidity of the archives, prevent the occurrence of malignant accidents. Application of temperature and humidity sensors simplifies the temperature and humidity record, saves the cost of cultural relics preservation and makes the work more scientific, prevents it from being disturbed by too much human factors.

After connecting the wires accurately according to the wiring diagram and powering on, the meter displays the thermocouple graduation firstly and then the range, measure the nixie tube on the lower part of the meter to display the setting temperature, and measure the nixie tube on the upper part of the meter to display the measuring temperature. If the upper nixie tube doesn’t display the temperature of the heating body but the other states such as “OVER”, “0000” or “000”, meaning that the output part of the meter goes wrong, following inspections shall be made:
Remove the thermocouple from the thermocouple output end of the instrument and then short circuit the thermocouple output end of the instrument with a wire. If the temperature showed on the upper nixie tube is close to the room temperature after powering on, meaning that exterior wire connection of the thermocouple disconnects, replace with a same thermocouple. If it keeps a same state as previous, meaning that the output end of the instrument is damaged in transportation, change an instrument please.

Cause of damage of parallel power capacitor

• When cutting off the capacitor bank, restriking overvoltage caused by breaker restrike leads to the insulation damage or breakdown between capacitors. Some capacitor banks don’t have any overvoltage protection measures nor series reactor, particularly, the frequently operated capacitors easily lead to insulation damage or even explosion.
• Too large current over the capacitor and overcurrent caused by overcurrent harmonics in power grid make the capacitor overheated, insulation reduction or even damage.
• The capacitor is not equipped with a single fuse or the fuse characteristics (characteristic aegis of ampere second) are too poor. When the internal components of the capacitor are seriously breakdown and the fault current is generated, the fuse can't fuse in time. Meanwhile, effective protective relaying measures fail to keep up, overcurrent leads to a sharp rise in the temperature inside the capacitor and thereof leads to capacitor expansion or explosion.
• Poor product quality. The paper oil insulation fails to be dried or dipping treatment under a strict vacuum condition, the residual bubbles inside produce partial discharge under the long-term working voltage, while partial discharge further leads to insulation damage and aging. As a result, the temperature also rises, which eventually leads to electrochemical breakdown of components and the capacitor damages.

When a new system is used for the first time or the meter, sensor is replaced, calibration must be made before use.
There are two kinds of calibration in general, one is the physical calibration (in this mode, two points needs to be calibrated, namely the zero position and the range), and another is the digital calibration.

Physical calibration is applicable for most weighing systems, and digital calibration is used in the fields when the physical demarcation can't be used. However, digital calibration can't eliminate the errors, its accuracy is related with the sensor’s sensitivity, range and wiring system (four-wire or six-wire), the division value or maximum range setting, as well as the signal loss on the junction box and cable.
The scale division and maximum range shall be set before calibration.
Before calibration, the instrument shall be powered on for at least 15 minutes until the sensors and meters reach the thermal equilibrium state.

1. Device lifetime
In the broad sense, the inverter is a Switching Mode Power Supply, so its components can be basically divided into resistor, capacity, diode power devices (IGBT or MOS tubes), inductor and transformer, current sensor, IC, optocoupler and relay.
Generally, service life of the resistor, chip capacitor and ceramic capacitor can be more than20 years. Theoretically, the inductor and transformer are defaulted to work for long time without failure on the design if only not exceeding the material temperature. Diodes and triodes with small power can work more than 100 thousand hours basically; The mechanical life of the relay is generally more than 1 million times and the electrical life is more than 10 thousand times; Generally, power device IGBT or MOS do not consider the life as long as they meet design specifications. The fan and fuse are vulnerable components, they will not affect the service life of the inverter, and they can be replaced as long as they break; service life of the film capacitor is more than 100 thousand hours and that of electrolytic capacitor is 2000-3000H at 105℃, the service life may also be 5000-6000H, and it doubles as the temperature decreases 10℃. Therefore, the weakest device of the inverter lies in the service life of the electrolytic capacitor.

1. Please don’t operate the visible spectrophotometer casually when you don’t know its performance deeply, operations shall be carried out under the guidance of operators skilled in the visible spectrophotometer.

2. Pay attention to sunscreen, anti drenching, damp proof and anti vibration. In case the visible spectrophotometer is dampened, put it in a cool and ventilated place, package after drying.

The gas analyzer is a flow analysis instrument for the measured gas composition. In many production processes, especially those with chemical reactions, it is often not enough to automatically control processes according to physical parameters such as temperature, pressure and flow. There are many kinds of gas analyzers due to the diversity of the gas types being analyzed and the analytical principles. The commonly used gas analyzers include infrared gas analyzers, laser gas analyzers, ultraviolet gas analyzers, thermal conductivity gas analyzers, electrochemical gas analyzers, etc. The gas detector is a kind of gas leak concentration detection instrument, including portable gas detector, handheld gas detector, fixed gas detector, online gas detector. The following is an introduction to the difference between a gas analyzer and a gas detector

Connector is also called as plug socket, it's widely used in all kinds of electrical circuits to connect or disconnect the circuit. The electrical connector has many types and wide applications, proper selection of circular connector is also an important way to improve the connector reliability.

Electrical parameter requirements

1. Rated voltage
   Rated voltage is also known as working voltage, it's mainly determined by the insulation materials used by circular connector and the distance between the contact pairs. Some component devices may not be able to perform their functions when using below the rated voltage.
2. Rated current
   Just the same as the rated voltage, the circular connector may not work normally in the current below the rated current. In the design of circular connectors requirements for rated current are met through the thermal design of the circular connector, because the contact pairs will be heated when current passed due to the existence of conductor resistance and contact resistance.

The detection modes of photoelectric sensor are divided into the following categories: opposite type, reflective plate type, polarizing reflective plate type, direct opposite type, wide beam type, focused mode, fixed-field type and adjustable-field type. Ultrasonic sensor includes two detection mode of opposite type and proximity.

Opposite type
Transmitter and receiver of the opposite detection mode are installed in an opposite mode, the light from the transmitter aims at the receiver directly. When the object blocks the beam, output of the sensor changes to indicate that the detected object is detected.
Reflective plate type
In the reflective plate detection mode, a sensor has both transmitter and receiver. The light emitted from the transmitter shines upon the reflective plate, the reflected light returns to the receiver. When the object blocks the beam, the detected object is detected.

What are the general debugging steps of the automatic transfer switch?

1. Put the double power on the adjustment table and connect the phase line and neutral line ( zero line).
2. For three-pole switch connection, the common and spare zero line need to be connected to zero line terminal (NN and RN).
3. After connecting lines, recheck the lines and then turn on the master switch of the commissioning table, turn on the common and standby power supply. 

In addition to comprehensive parameter testing and effective screening of relays, proper use of relays is also an effective way to improve the reliability of relays. Conversely, improper use will shorten the life of the relay. How to improve the reliability of the relay? Here are some suggestions for your reference.

• Reasonable selection of the working voltage of the relay
  The pull-in voltage of the relay is generally only one-half to two-thirds of its rated working voltage. However, when using the relay, it must work at its rated working voltage, but not the pull-in voltage as the working voltage. This is because, under the condition of the pull-in voltage, although the relay has been operated, the pressure between the moving contacts has not reached the specified value, which will cause the contact resistance between the contacts to be too large, if the contact at high current conditions, when working, it will increase the contact power, which will easily lead to contact ablation and shorten the working life.

Angle of measurement

In order to ensure accurate measurement, keep the infrared thermometer following the surface normal direction of the measured object as possible in measurement (perpendicular to the target surface). If you fail to guarantee the instrument in the normal direction, it is supposed to measure in 45 degree angles with the normal direction, otherwise the displayed value of the infrared thermometer will be low.

Industrial Personal Computer is called industrial PC for short, it's mainly used in the industrial production; Normal computer is called PC for short and is mainly used in personnel or business. Because of the different applications, the technical requirements are different. Ordinary household or office computer is a civil class, while the industrial PC is a industrial level, which has special requirements in structure and other aspects.
On the appearance, the normal computers are open with many heat dissipation holes on the appearance, only a power fan is used to blow outwards to dissipate heat. However, the industrial PC case is completely closed and it's much heavier than the normal computer, meaning that its material is thicker and stronger. It not only has a fan inside, but also another fan to ensure the positive pressure in the case.

Industrial PC is called industrial control computer for full, it is a computer specially designed for industrial control, and is used to monitor and control the machine equipment, production process and data parameters in the production of industrial control computers.
Industrial PC often runs in a bad environment and has higher requirements on the data security, so industrial PC usually has special design, such as reinforcement, dustproof, moisture-proof, anti-corrosion and radiation protection.
Industrial PC also has higher demand for expansibility, the interface design needs to meet specific external devices, so the industrial PC needs to be customized to meet the demand in most cases.
We should know the following clearly on how to choose an industrial PC: which equipment is the industrial PC used; if the communication interface of the industrial PC is sufficient; whether the product quality is up to the standard.