The secondary side is not allowed for open circuit. Once it's open circuited, current I1 at the primary side would fully turn to magnetizing current, φm and E2 would increase sharply. As a result, the iron core would occur supersaturation magnetization, heat seriously and even burn out coils. Meanwhile, supersaturation magnetization of the magnetic circuit would increase errors. Under normal operation, secondary side of the current transformer is nearly short circuited, if it's broken suddenly, the excitation electromotive force increases sharply, the magnetic flow in the iron core shows seriously saturated flat waves. As a result, the secondary side winding would induce high spike waves when the magnetic flow passes through zero, it can be thousands or even tens of thousands of volts, thus endangering the personnel safety and insulation performance of instruments.
Blog
Soft starter is used for controlling AC induction motor in soft start & soft stop. It applies to various squirrel-cage asynchronous motor control of load, the motor can smooth starting under any working conditions, protect the drag system, protect motor from inrush current and voltage impact, ensure reliable motor starting. Smoothly soft stopping function can effectively solve the inertial system surge problem, and eliminate the drag system of inertial impact.
Common fault for the iron core of an AC contactor is about the large noise. If it's caused by insufficient coil voltage after inspection, adjust the power voltage. If it's caused by bad contact between contact surfaces of dynamic and static cores, make contact surfaces smooth to ensure a good contact. If the noise is caused by the break of short circuit ring, replace or weld the short circuit ring. Another common fault is that the armature doesn't fall when powering off. This may be caused by small spring pressure between contacts, adjust the contact force please. If it's caused by block of armature or mechanical part, remover the barrier. There should be a clearance of 0.1～0.2mm in the central pillar of E-shaped core, if the clearance disappears due to iron core wear, the iron core may be stuck, repair the central pillar plane of the E-shaped core.
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?
In primary treatment, the suspended solid pollutants in the sewage will be removed, and most physical treatments can only meet the requirements of primary treatment. After the primary treatment, 30% BOD can be removed from the wastewater. It doesn’t meet the emission standard. Primary treatment is a pre treatment of secondary treatment.
In secondary treatment, colloid and dissolved organic pollutants (BOD, COD) in the waste water will be removed, and the removal rate can be higher than 90%. The organic pollutants meet emission standards. Use pH meter to monitor whether the emissions of organic pollutants are up to standard.
In tertiary treatment, non biodegradable organic pollutants, N, P and other soluble inorganic substances that lead to eutrophication of water bodies are further processed. Main methods are biological nitrogen and phosphorus removal method, coagulant sedimentation method, sand filtration method and activated carbon adsorption method.
The infrared thermometer is used for measuring the surface temperature of the object. ATO infrared thermometer is non-contact, handheld and easy to operate, especially suitable for measuring the temperature of various hot, hazardous or hard-to-reach objects. This infrared thermometer consists of Optics, temperature sensors, signal amplifier, processing circuit and LCD display. The Optics collects the infrared energy emitted by the object and focus it to the sensor. Then the sensor transforms the energy into an electricity signal. The signal will be turned into a digital number shown on the LCD after the signal amplifier and processing circuit.
Voltage stabilizer is a kind of power supply equipment which can automatically adjust the output voltage. Its function is to stabilize the power supply voltage which fluctuates greatly and cannot reach the requirement of electrical equipment within its set value range, so that various circuits or electrical equipment can work normally under rated working voltage. With the increasing number of household electrical equipment, the use of voltage stabilizer is more and more extensive. Domestic voltage stabilizer is mainly used to stabilize the voltage of TV, refrigerator, air conditioner, etc. Next, ATO will show you how to install a voltage stabilizer for home.
1P, 2P, 1P+N, 3P, 4P, 4P+N, P means that the miniature circuit breaker (MCB) is equipped with a protective pole (knife pole), N means that the neutral conductor is only equipped with knife pole, but no protection modules. Both 2P and 1P+N are called two pole switch, 4P and 3P+N are called 4 pole switch. Neutral conductor of 1P+N and 3P+N don't have protection, so they are much cheaper, the neutral conductor pole acts along with the phase line pole. Some circuit breakers divide 1P+N into two types: one adopts two module width, another adopts one module width (small size). For these poles, how to select a right miniature circuit breaker?
Current transformer consists of closed iron core and winding. It has few primary winding that are connected in series in the current circuit under measurement; however, it has many secondary winding, which are connected in series in the measuring instrument and protection circuits. The current transformer plays the role of converter and electrical isolation, it's a sensor for measuring instrument, relay protection and other secondary equipment to obtain current information of primary circuit in power system. It converts the high current to a low current by ratio, its primary end is connected with the primary system, while the secondary end is connected with the measuring instrument and relay protection.
A conductor will produce magnetic field in a certain range of space it occupies when it's powered on, so all electric conductors carrying current are inductive on a general sense. However, a long straight conductor often generates a small inductance, the generated magnetic field is not strong, so the actual line reactor is a wire wound solenoid, which is also called air core line reactor. Sometimes an iron core would be inserted into the solenoid to generate greater inductance, which is called iron core line reactor. Reactance is divided into inductive reactance and capacitive reactance, in the more scientific division, both impedor (inductor) and reactance (capacitor) are called line reactor. However, as inductor appeared earlier and was called line reactor, the capacitor people often say only refers to the reactance, and line reactor refers specifically to the inductor.
Main function of three-phase output line reactor is to compensate the influence of long line distributed capacitance, restrict the output of harmonic current and improve output high frequency impedance, thus protecting the inverter.
Safety light curtain is a powerful safety laser sensor for machine guarding and personal safety. It is rather convenient and flexible in wiring and installation. The safety light curtain is equipped with flexible and relevant software, which can easily change the shielding and blanking effect according to the customers' various on-site requirements. It greatly reduces the time for re-arrangement and re-wiring. However, due to the complexity of the production process, the on-site product models often change, the settings for the safety light curtain also change accordingly. There are still some common problems in installation and maintenance. Today, ATO will tell you how to solve these problems.
Load cell is based on the principle that resistance changes when the resistance strain gauge pasting on the surface of elastomer is forced deformation. Load cell converts the change of resistance to mV signal so as to complete the process of converting external force into electrical signal. According to its principle and structure, the fault of strain gauge load cell is often caused by some human or natural factors.
Current-limiting start mode
When the motor starts, the output voltage increases rapidly until the motor current reaches the set current-limiting value and then keeps below the set value. As the output voltage gradually increases, the motor speeds up. When the motor reaches the rated speed, the bypass contactor attracts, the output current drops rapidly to the rated current or below, the starting is thereof completed.
When the motor load is lighter or the setting value is rather larger, the maximum starting current may not reach the set current-limiting value. Current-limiting mode is generally applicable for situations that has strict restrictions on starting current.
Digital counter is a LED control meter that can be used for counting (number/length/footage/batch/event/time), measuring (frequency/rotational speed/linear speed/flow) and position control. The most common way is to connect a digital counter with a photoelectric sensor or a rotary encoder to form a number counting system. The photoelectric sensor or rotary encoder outputs signal for counting number, and the digital counter displays the counting number. Another way, after the digital counter SV is set, once the counting number PV reaches SV, the digital counter internal relay will operate and alarm to realize process control.
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.
Side blow of static contact and moving contact knife in closing
The fault cause is that the inappropriate position of static contact and moving contact knife causes side blow in closing. Check whether the fastening screw of moving contact knife of disconnect switch is too loose or too tight. Check whether the split ring on both sides of static contact of fuse type disconnect switch has movement or deforms or is damaged owing to poor contact, overheating or annealing.
Solution: adjust the degree of tightness and position between blades of fastening screw of level 3 moving contact, adjust the degree of tightness of moving contact knife, adjust moving contact knife to the center between moving contact knife and static contact, no side blow in closing test, no jam in closing. Fuse type disconnect switch adjusts the split ring on both sides of static contact to put the gap between static contacts at the center line of blades of moving contact knife. Then, conduct closing test.
1 Electromagnetic Design
For a common asynchronous motor, major performance parameters considered in design include the overload capacity, start performance ,efficiency and power. As for a VFD, its breakdown slip is inversely proportional to the power frequency, and it can start directly when the breakdown slip is near 1, therefore, the overload capacity and start performance doesn’t need to consider, the key problem to be solved is how to improve the adaptability of the motor to non sinusoidal power supplies. Methods are as follows:
Connect the positive and negative electrode of a 1.5～3V battery with the primary coil L1 and L2 of the transformer respectively, connect the transformer’s secondary side K1, K2 respectively with the positive and negative electrode of a milliammeter. After the loop is well connected, the indicator of milliammeter turns clockwise while connecting K, and turns anticlockwise while disconnecting K, that means the transformer's terminal connecting with the positive electrode of the battery has the same polarity with the terminal connecting with the positive end of the milliammeter, namely L1 and K1 have a same polarity and the transformer is a subtractive polarity. If the indicator turns conversely to the above, the transformer is an additive polarity.
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.
