Test method of transformer 1.Check whether there are obvious anomalies by observing the appearance of the transformer. Such as whether the coil lead is broken, de-soldering, whether the insulation material has burnt marks, whether the core fastening screw is loose, whether the silicon steel sheet is corroded, whether the winding coil is exposed, etc. 2.Insulation performance test. Use the multimeter R×10k stop to measure the resistance value between the core and the primary, the primary and the secondary, the core and the secondary, the electrostatic shielding layer and the secondary and secondary windings, and the multimeter pointer should mean that the infinite position is not moving. Otherwise, it indicates that the insulation performance of the transformer is poor. 3.Coil on and off detection. The multimeter is placed in R×1 gear, and in the test, if the resistance value of a winding is infinite, it indicates that this winding has […]
E&I Articles
Principle and Structure of Transformer The transformer is a device that uses the principle of electromagnetic induction to change the AC voltage, and the main components are the primary coil, the secondary coil and the core (magnetic core). In electrical equipment and wireless circuits, it is commonly used for lifting voltage, matching impedance, safety isolation, etc. In a generator, whether the coil is moving through a magnetic field or the magnetic field is moving through a fixed coil, the electric potential can be induced in the coil. In both cases, the value of the magnetic flux is unchanged, but the number of magnetic flux of the chain intersecting the coil is changed, which is the principle of mutual induction. A transformer is a device that uses electromagnetic mutual inductance to transform voltage, current and impedance. Transformer components include the body (iron core, winding, insulation, lead), transformer oil, fuel tank and […]
Basic knowledge of electric cabinet There are two types of electric cabinet, one is the distribution cabinet, the other is the control cabinet. From the perspective of structure, the electric cabinet is composed of a shell, steel structure and various mounting plates, as well as components, instruments, measurement and control devices and cables. There are partitions in the electrical cabinet. The partition includes bus compartment, component compartment, outlet compartment and so on. Compartments exist to avoid arc shock and temperature rise. We call the power transmission and control loop the primary loop, the implementation of measurement and control, data acquisition and amplification, display, information exchange loop called the secondary loop. Accordingly, the components in the electrical cabinet are also divided into primary circuit components and secondary circuit components. In addition, the primary loop is also called the main loop, and the secondary loop is also called the control loop. For […]
As a kind of elastic compensation element, expansion joint has the advantages of reliable operation, good performance and compact structure, and has been widely used in chemical industry, construction, water supply, drainage, petroleum, light and heavy industry, refrigeration, health, water heating, fire protection, electric power and other basic engineering fields, playing an important role in people’s life.What is an expansion joint?The expansion joint is also called the compensator, which is a flexible structure set on the container shell or pipe to compensate for the additional stress caused by temperature difference and mechanical vibration. Expansion joints are divided into metal expansion joints and non-metal expansion joints.Below, please compare the performance difference between metal expansion joints and non-metal expansion joints with Xiaobian, so as to have a more in-depth understanding of expansion joints. As an important category of non-metallic expansion joints, rubber expansion joints have a large displacement compensation ability, which can […]
Cause Analysis and Solution of Numerical Jumping When Digital Multimeter Measures The Resistance Value of Motor In the process of motor maintenance and inspection, it is a common method to measure the resistance value of motor winding with digital multimeter. However, sometimes the digital multimeter will encounter the problem of numerical jumping when measuring, and can not obtain stable measurement results, which brings trouble to judge whether the motor is burned out. This paper will analyze the reasons of numerical jumping when the digital multimeter measures the resistance value of the motor from many angles, and give the corresponding solutions. First of all, the motor has not completely stopped running is an important cause of numerical jumping. When the motor stops, due to the remanent magnetic action of the rotor, the induction voltage will pulsate in the motor winding. This induced voltage interferes with the measurement of the digital multimeter, […]
Fault Mechanism and Detection Method of Rectifier Circuit Rectifier circuit is an indispensable part of electronic equipment,its main function is to convert AC power into DC power. However,in the course of use, the rectifier circuit may also have various faults. This paper will analyze the fault mechanism of the rectifier circuit in detail, and provide effective detection means. 1.Failure mechanism The fault of the rectifier circuit is mainly related to the rectifier diode, and there are two possible reasons: one is the destructive influence of the external circuit on the rectifier diode; The second is the quality of the rectifier diode itself. The rectifier diode may have two kinds of hard faults, such as open circuit and breakdown, and soft faults such as forward resistance increase and reverse resistance decrease, which will affect the working stability of the rectifier circuit. 2.Key test points The key test point of the rectifier […]
Rules and Causes of Overheating of Electrical Equipment 1. External thermal faultExternal thermal failure of electrical equipment mainly refers to the exposed joint due to poor crimping and other reasons, under the action of high current, the joint temperature increases, the contact resistance increases, and the vicious cycle causes hidden dangers. Such failures account for more than 90% of external thermal failures. Statistics of thousands of external thermal failures detected in recent years, you can see that the thermal failure of wire clamp and brake contact accounts for 77% of the entire external thermal failure, their average temperature rise is about 30 ° C, the average temperature rise of other external joints is between 20-25 ° C, combined with the detection experience in recent years, according to the number of temperature rises, External failures can be divided into three types: minor, general and serious. 2. Internal thermal failureThe internal thermal […]
Solenoid valve selection and working principle Solenoid valves are divided into three categories in principle: 1) Direct acting solenoid valve: Principle: When energized, the electromagnetic force generated by the electromagnetic coil lifts the closing part from the seat, and the valve opens; When the power is off, the electromagnetic force disappears, the spring presses the closing part on the seat, and the valve is closed. Features: It can work normally under vacuum, negative pressure and zero pressure, but the diameter is generally not more than 25mm. 2) Distributed direct acting solenoid valve: Principle: It is a combination of direct action and pilot principle, when there is no pressure difference between the inlet and the outlet, after the power is turned on, the electromagnetic force directly lifts the pilot small valve and the main valve closing part in turn, and the valve opens. When the inlet and outlet reach the starting […]