Tag: how to

Cause of current transformer burning up

•  Secondary open circuit of the current transformer produces high voltage to burn out the current transformer.
• Long-term use of the current transformer makes the insulation aging, local breakdown or discharge occurs and overvoltage is thereof produced, thus burning out the current transformer.
• The aluminum contact surface of current transformer’s primary connection is seriously oxidized, which results in large contact resistance. The contact resistance gives out heats and burns out the current transformer
• Long-term overload operation makes the current transformer to give out heat, it is thereof burned out.

The vibration frequency of body is not in line with that of grading ring. Owing to the damping of transformer oil, grading ring has a low vibration frequency. And owing to single point welding and aluminum sheet welding, it has a poor mechanical strength. In the long-term operation, the vibration brought by the inconsistent vibration frequency of earth tag of line reactor (aluminum, welding) and grading ring causes metal fatigue and cracks. Solution: fix ascending flange base and body to reduce free-running vibration.

Displacement sensor, also called linear sensor, is a linear unit sensing metal. The function of sensor is to transform the tested physical quantity into electric quantity. The working principle of straight line displacement sensor is same as that of slide rheostat. It is used as voltage divider to present the actual position of tested position through relative output voltage. There are a few requirements for the work at the position:

Oil replacement and drying treatment of electric reactor: if the long idle time or operation time or other nature and human factors cause insulation deterioration of line reactor, water inflow or oil deterioration, oil replacement and drying treatment should be conducted to line reactor. Oil replacement of line reactor: lift the body of line reactor out, drain sump oil, wash oil tank, and wash the greasy dirt on the body of electric reactor if any. After drying, fill electric reactor with oil and replace all grease-proof rubber seals. Theline reactor can be operated only after passing the test.
Drying treatment of line reactor: its body has many drying methods. Users can adopt zero phase sequence drying method, eddy drying method, short circuit drying method and oven drying method when they dry line reactor by themselves.

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.

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.

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. 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.

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.

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.

In practical application, after human body intrudes into the range of safety light curtain, besides that safety light curtain needs certain response time, the machine also needs certain braking time. Therefore, to guarantee personal safety of operators, installation position of safety light curtain must meet requirements of safety distance. Otherwise, there is still the possibility of an accident.

Switching power supply (SMPS) is widely used due to its compact size, light weight and high efficiency. But it has its own disadvantage of producing noises, which not only affect the normal operation of the circuit, but also interfere with the neighboring electronic equipment. So how to reduce the noise of SMPS? First of all, we need know where the noise comes from, and then we can eliminate it accordingly.
The noise of switching power supply can be divided into two major categories: one is the interference formed by the internal components of SMPS, and the other is the interference caused by the external factors. There are many sources of noise, such as external interference like lightning, mechanical vibration, poor contact and so on. Besides, improper design of circuit, improper parameter selection of components, unreasonable layout and wiring will also increase the power supply noise.

How to choose a right switching power supply? Six tips will give you a guide of selecting a right SMPS power supply: voltage, power, load characteristics...
How to use a switching power supply properly? To use a SMPS power supply properly and in long service life, some suggestions are made for your reference.

Power line filter is electrical equipment which effectively filters particular frequency point in the power line or the frequency out of the particular frequency point. It is a passive bi-directional network, that is, one end is power supply, and the other end is load. When selecting an EMI power line filter, what should be taken into considerations? Rated voltage, rated current, insertion loss...

How to select a right solid state relay? When selecting solid state relay(SSR), it should be based on the actual application conditions and SSR performance parameters, and especially take into consideration the overcurrent and overvoltage conditions in the use and the load capacity of SSR, which is helpful to achieve the long life time and high reliability of solid state relays. Then, follow the questions and find the detailed answers to choosing a right  SSR.