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The relay contacts’ jumping or switching on/off will cause the change of inductive load and further gas discharge. The current of relay contact on-off is small, there will be no electrical arc between contacts, but there will be a spark at the relay contacts. Due to the existence of inductance in the contact circuit, there will be overvoltage on the inductance when disconnecting the contact circuit. Together with the voltage supply in the contact gap, the contact gap that just separates a little will be broken down and discharged. Limited to energy, there will only be spark discharge. The conversion of capacitance between contacts and energy in inductance makes spark discharge disappear and reappear, becoming a high frequency signal, which will be crosstalk to related circuits by means of high frequency radiation, wire transmission and distributed capacitance, forming interference signals. Furthermore, spark discharges can also damage relay contacts and shorten the service life of contacts, so that sparks may ablate contact surfaces and make the surface uneven, resulting in failure of relay poor contact.

When using uninterruptible power supply (UPS) system, people tend to unilaterally believe that there is no need to maintain batteries. However, the data show that there is about one third UPS host failure or abnormal operation caused by battery failure. Therefore, it is more and more important to strengthen the proper use and maintenance of UPS battery for prolonging the service life of batteries and then reducing the failure rate of UPS system.

Step up or step down transformer is an important part of power grid operation, it's of great significance to the stable operation of the power grid. It meets different power demands by adjusting current and voltage. Once a transformer fails, it will cause great losses to the whole power grid, and further affects the normal operation of industrial production. In order to ensure the efficient operation of transformers, it is necessary to carry out a comprehensive management of the whole process of installation and application, thus reducing potential safety hazards and improving operational efficiency.

Nowadays, the magnetic flow meter (electromagnetic flow meter) has been widely applied to measuring of industrial sewage or wastewater. With a high precision and a long service life, the magnetic flow meter is the top choice for the environmental measuring industry. To choose the correct magnetic flow meter can five fuller play to the magnetic flow meter for specific purposes. Generally, the selection of the magnetic flow meter is based on the following factors including chemical attributes of the fluid medium, pipeline diameter, flow range, liner material, electrode material and output signal.

The AC contactor has found wide applications in the motor-controlled circuit. It is no exaggeration to say that the electric drive of most motors cannot be separated from the control of the AC contactor. Many electricians are very familiar with the AC contactor for their frequency use or maintenance of it. How should we calculate the AC contactor rating for the motor or other equipment and make a right choice? Let us take a look at it.

Modern industrial sensors are vastly different in principle and structure, and there are so many different types of products on the market. How can we find the ideal sensor for a specific application? When the sensor is selected, the corresponding measurement method and measuring equipment can be determined. The success or failure of measurement results largely depends on whether the selection of sensors is reasonable.

With the rapid development of industrial automation, the variable frequency drive, used for frequency conversion debugging, is thereof widely used. As an important role of frequency conversion speed regulation and energy saving, VFD is mainly used to control the AC motor's power control equipment by changing the frequency of the motor's working power supply. It's not only advantageous for improving the enterprise's process and production level, but also plays an important role in energy saving. But how should we choose an appropriate VFD?

Load capacity of soft starter mainly refers to the overload capacity. Due to different working system, actual load capacity of soft starter is also different. For example, the soft starter generally bears a current of 2~4 times of rated current at starting process, and the duration is within 60s. For long-term working systems, the soft starter actually works under short-term overload during starting process. But for short-term working systems, the soft starter actually works under long-term overload during starting process. Thermal capacity of power semiconductor devices (thyristors) is very small, so the overload capacity of devices mainly depends on the overload capacity of power conductor devices and heat dissipation capacity of soft starters.

With the three-phase reactor, in regulating the speed of the original power frequency excitation, the establishment of the feedback voltage maintains the excitation current in the excitation coil to be in a rather small amplitude, which will basically not exceed the maximum value. It can reach the maximum value unless it is in full-speed operation status. The three-phase reactor is widely used in the elevator, wind power generation, solar power generation, railroad engine, metro, machine tool, welding machine, industrial washing machine, airplane, ship, electromechanical laboratory of the university and other fields.

When we get a pressure transducer, it's necessary to do detection for it. The easiest way to test a pressure transducer is to connect it to a display instrument directly. And check whether the display value changes with the pressure. If it is ok. We have to do further detection for the pressure transducer.

Inverter is a kind of transformer converting the low-voltage DC power (usually such as the power output by the battery) into the high-voltage AC high-frequency power (sine wave AC power of 220V 50Hz or 110V 60Hz). Take a 12V DC to 220V AC car power inverter as example to illustrate the working principle briefly. Firstly, the 12V low-voltage DC power in the vehicle is converted into the high-voltage DC power of around 265V, and then the 265V DC power is converted into the sine wave AC power of 220V, 50Hz. The main inner components of power inverter include the Inverter Bridge, filter circuit, oscillator, control logic circuit and so on. At present, a large amount of various power inverters are filled in various e-commerce platforms. The cheapest one is only tens of dollars, but the expensive ones can cost several hundreds or even one thousand dollars. The maximum power it sustains range from dozens of wattages to several hundreds of wattages. Then, what kind of power inverter can we choose?

As to the ripple wave of the switching power supply, it certainly exists both theoretically and practically. Generally speaking, here are some approaches restraining or reducing it.
Reducing EMI - diode back connection inductance
The metal shell can be adopted as the shield which is used to reduce the radiated interference of the external electromagnetic field. In order to reduce the electromagnetic interference of the power line input, the power input terminal is equipped with the EMI power line filter, just as the below diagram shows (EMI filter is also named as the power line filter). This is also a method usually used to restrain the high-frequency noise.

Gas detectors are widely used in petrochemical, environmental protection, gasoline, coal mining and other industries. For all kinds of different safety production occasions and testing requirements, the selection of a suitable gas detector must be very important for every person engaged in safety and health work.
First of all, confirm the type and concentration range of the gas to be tested. The type of gas encountered in each production department is different. All possible situations should be considered when selecting a gas detector.
Then, choose differet types of gas detector based on industrial environment - fixed gas detector and portable gas detector.

For some Microcontrollers, the resistance of sensor connected must be less than 10kΩ when carrying out the A/D transformation. For example, the resistance of Analog Devices's analog acceleration sensor is 32kΩ. It can’t work normally on the PIC and AVR control board. So it’s suggested to read the controller manual carefully before purchasing the sensor, so as to ensure that the sensor can work normally.

The load cell has a certain overload capacity, but it shall still be prevented from overloading in installation. It should be notified that even a short-term overload can still cause permanent damage to the sensor. During the installation, a pad with the same height of the sensor could be firstly used instead if necessary, then replace the pad with the sensor. In normal operation, the sensor should generally be equipped with mechanical structure for overload protection. If the sensor is fixed with screws, the screw should have a certain fastening torque and screwing thread depth. Generally, high strength screws should be used.

Measurement method of a safety relay's DC resistance with a digital multiemter is similar to that with a pointer multimeter. According to the nominal DC resistance of safety relay, place the multimeter in an appropriate resistor and connect two test pens to the leading wire of the relay coil, then measure the resistance. Comparing the measurement result with the nominal resistance, if the error is within ±l0%, it's normal. If the resistance is obviously smaller, partial short-circuit fault exists in the coil; If the resistance is zero, the coil is short circuited; If the multiemter shows "1", the coil breaks.

Measure coil resistance, resistance of a power relay coil can be measured with the R×10Ω band, thus judging whether the coil has open circuit. Measure actuation voltage and actuation current, with an adjustable stabilized voltage supply and ammeter, the power relay can be input with a voltage while the ammeter can be connected in series to monitor. Slowly increase the power supply. Voltage and record the actuation voltage and actuation current when the power relay is attracted. For accuracy, more operations can be repeated to get the average value. Measure release voltage and release current, connect wires as the test above. When the power relay is attracted, reduce the power supply voltage slowly and record the voltage and current as hearing the relay to release again. More operations can be repeated to get the average value.

Oil leakage is a common problem for gear motor, and the problem may be caused by box quality, lubricating oil quality, oil seal quality and air pressure outside and inside the box. Meanwhile, excessive lubricating oil will also lead to oil leakage. Once the oil leakage occurs in the gear motor, corresponding measures should be taken, and this paper ATO will introduce the solutions for stopping gear motor oil leakage.

Gear motor is widely used in the metallurgy, mine, light industry, chemical industry, steel industry, cement, printing, sugaring, food industry, construction, lifting transportation and fan industry. Working environment of these industry may be damp, and damp environment will directly affect the operation of gear motor. How to keep your gear motor dry when works in such a damp environment?