Electrical Encyclopedia: High-voltage switchgear, busbar bridge and transformer connection method
1. The current is transmitted along the metal conductor. The busbar is made of metal material. In the circuit, the function of the busbar is to transmit electrical energy.
2. The function of the busbar bridge is to fix the busbar inside, and to support, fix, protect, and dissipate heat.
3. The incoming line cabinet is mainly the switch cabinet. The inside is mainly the circuit breaker and other equipment. There are also busbars inside. The electric energy is passed from the outside of the incoming line cabinet to the circuit breaker through the busbar, and then the busbar is passed through the busbar. Come out, after a certain distance, to the transformer, complete the control and protection of the transformer. However, the distance from the incoming cabinet to the transformer may be very long. In order to protect the busbar and protect the person who may be close to the busbar, the busbar bridge is used to close the busbar to protect the busbar.
Schematic diagram of switchgear, busbar bridge and transformer
Electrical Encyclopedia: The main reason for circuit breakers false tripping
The main reasons for the accidental tripping of the circuit breaker are: personnel misoperation, self-tripping of the operating mechanism, and electrical secondary circuit problems.
1. When the circuit breaker is accidentally tripped, first check whether it is a personnel misoperation. There are two cases of personnel misoperation: one is the operation error; the other is the misoperation caused by improper protection measures on the relay protection circuit.
2. If it is not a mistake, check the operating mechanism for malfunction. For example, whether the circuit breaker tripping mechanism is faulty or whether the circuit breaker automatically trips due to external vibration.
3. If the operating mechanism is checked, it may be caused by two-point grounding in the operating circuit, causing the circuit breaker to automatically trip, or the operating circuit is short-circuited, or some components in the operating circuit, such as anti-skip relays, may cause poor performance. False trip.
If the insulation state of the inspection circuit is good, the relay protection device should be inspected to check whether the protection device malfunctions and the circuit breaker automatically trips. In order to ensure the power supply to the user, after the line circuit breaker is automatically tripped, the manual or automatic reclosing device can be used for closing.
Electrical Encyclopedia: Circuit Breaker Rejection Failure Handling Procedure
To handle the circuit breaker rejecting the closing fault, it must be good at distinguishing the fault range. The processing steps are as follows:
1. First determine whether the circuit breaker is combined with the pre-volt fault line to cause a trip. The meter can indicate the impact swing caused by the short-circuit current during the closing operation and the sudden darkening of the illumination lamp. The voltmeter indicates a sudden drop to judge. . If it is determined that the line is faulty, isolate the fault area and then cast the circuit breaker.
2. If it is determined that it is improperly operated, check whether there is a lock-up insurance, whether the control switch is reset too fast or not, and whether the transfer switch is in the correct position.
3. Check if the operation closing power supply voltage is too high or too low, check whether the operation closing insurance is blown or poorly contacted, check whether the control switch and the auxiliary contact are in poor contact, whether the circuit is broken or the wiring is wrong.
4. Check if the operating mechanism is stuck and the auxiliary contacts and mechanism are not properly adjusted.
Generally, the gap between the connecting parts of the operating mechanism is unqualified, and it is necessary to inspect and replace the new high-hardness qualified parts.
Electrical Encyclopedia: How to detect capacitors
Capacitors are both the most common electrical components. It is also an easily damaged electrical component. To detect the quality of a capacitor without special instrumentation, the following methods are available:
1, multimeter detection method
For fixed capacitors above O.01μF. The R×1k block of the multimeter can be used to directly test whether the capacitor has a charging process and whether there is an internal short circuit or leakage, and the capacity of the capacitor can be estimated according to the magnitude of the amplitude of the pointer swinging to the right. When testing, first touch the two pins of the capacitor with two meter pens, then change the test pen and touch it again. If the capacitor is good, the multimeter pointer will swing to the right and then quickly return to the infinity position to the left. The larger the capacitance, the greater the swing of the pointer. If the two fingers of the capacitor are touched repeatedly, the pointer of the multimeter will not swing to the right, indicating that the capacity of the capacitor has been less than 0.01μF or has disappeared. During the measurement, if the pointer swings to the right, it can no longer return to the infinity position to the left, indicating that the capacitor is leaking or has broken down.
2, fuse simple detection method
Use a fuse (the rated current In of the fuse is determined by: IN = 0.8 / C (A), where C is the capacitance of the capacitor) and the capacitor to be tested is connected in series to the 220V AC power supply, if the fuse The fuse is broken, indicating that the capacitor has been short-circuited inside. If the fuse of the fuse does not break, after a few seconds of charging, cut off the power supply, and use a screwdriver with an insulating handle to short-circuit the two poles of the capacitor. A spark occurs and the capacitor is good. Conversely, it indicates that the capacitance of the capacitor has become smaller or has been opened. Use this method to judge whether the capacitor is good or bad should be repeated several times to get the correct conclusion.
3, incandescent bulb and capacitor series detection method
Connect the incandescent bulb and capacitor in series with the 220V AC power supply. If the brightness of the incandescent bulb is darker than connecting it directly to the 220V AC power supply, the capacitor is good. If the incandescent bulb is not lit, the inside of the capacitor to be tested is indicated. The circuit has been disconnected; if the brightness of the incandescent bulb is the same as the brightness of the direct connection to the 220V AC power supply, the internals of the capacitor have been shorted.
4, megohmmeter detection method
It can also be detected with a megohmmeter (250V class). Shake the handle, such as the pointer is at infinity, indicating that the capacitor is internally open; if the pointer is at zero, it indicates that the capacitor is internally shorted. It can also be used as a ground test for capacitors by connecting the terminals of the megohmmeter to the terminals and housing of the capacitor. Shake the handle, such as the pointer at zero, indicating the internal ground of the capacitor.
5, the measurement of capacitor capacitance
The capacity of the power capacitor can be measured with a multimeter without a dedicated meter. The specific method is: using a fuse (the specification is determined by the capacitance of the capacitor) and the capacitor to be tested are connected in series to the 220V AC power supply. Use the multimeter's AC voltage file to measure the voltage across the capacitor, U(V).
The current I (mA) through the capacitor is measured with the multimeter's AC current file. Since I=U/XC and XC=1/(2πfC), where f is the frequency of the alternating current. Therefore, the capacitance of the capacitor CC = 3.18 × (I / U) (micro method).
Electrical Encyclopedia: Main points of routine maintenance of electric motors
The main point of daily maintenance inspection of the motor is to find out the abnormal state of the equipment early and handle it in time to prevent the accident from expanding. The maintenance personnel can find abnormal phenomena according to the action and signal of the relay protection device, and can also rely on the experience of the maintenance personnel to judge the accident.
1, the first is the visual inspection
By visually, the following anomalies can be found: whether the external fasteners of the motor are loose, whether the parts are damaged, whether the surface of the equipment is oily or corroded, whether there are discoloration, burn marks and smoke marks at the contact points and joints of the motor. phenomenon. The reason for these phenomena is due to local overheating of the motor, poor conductor contact or burnt of the windings; If the voltmeter is not indicated or is abnormal, it indicates that the power supply voltage is unbalanced, the fuse is blown, the three-phase resistance of the rotor is unbalanced, single-phase operation, and poor conductor contact. If the ammeter indication is too large, it indicates motor overload, bearing fault, winding turn-to-turn short circuit, etc.; motor stalls, caused by: power failure, single-phase operation, low voltage, too small motor torque, excessive load, voltage Falling too large, bearing burned, mechanically stuck, etc.
2, using the auscultation stick to hear the various noises of the motor by hearing
These include electromagnetic noise, ventilation noise, mechanical friction sound, bearing noise, etc., so that the cause of the motor failure can be judged. The causes of noise are mechanical: bearing failure, mechanical imbalance, loosening of the fastening screw, non-conformity of the coupling connection, rubbing of the stator core, etc.; electrical: voltage imbalance, single-phase operation, winding There are open circuit or breakdown failures, poor starting performance, and poor acceleration performance.
3, by smell, you can find the cause of burnt smell, odor caused by: motor overheating, winding burnout, single-phase operation, winding faults, bearing failures.
4, by touching the surface of the casing by hand, you can find the temperature of the motor is too high and the vibration phenomenon
The causes of vibration are: unbalanced mechanical load, looseness of various fastening components, insufficient strength of the motor base, improper coupling of the coupling, uneven air gap or mixed debris, voltage imbalance, single-phase operation, winding failure, Bearing failure, etc.
The cause of excessive motor temperature is overload, cooling air duct blockage, single-phase operation, turn-to-turn short circuit, high or low voltage, three-phase voltage imbalance, poor acceleration characteristics, long starting time, stator and rotor phases. Bad contact of the wiper, starter, frequent start and brake or reverse brake, excessive inlet air temperature, mechanical jam, etc.
Electrical encyclopedia, industrial website Daquan, industrial encyclopedia, electrical headlines, industrial headlines, industrial video, industrial live broadcast, industrial pictures, industrial talents, electric number, electric world, I know best! World industry, industrial data, equipment industry, raw material industry, consumer goods industry, energy industry, transportation equipment, electronic information, industrial software, industrial enterprise, industrial logistics, industrial design, industrial achievement, industrial technology, industrial culture, industrial figures, industrial think tank , talent recruitment, industrial exhibitions.
When the temperature of the motor is estimated by hand to estimate the temperature, since each person's feeling is different and subjective, it is determined by experience.
Routine maintenance inspections are divided into daily inspections, monthly or periodic inspections, and annual inspections.
In the daily inspection, the main inspection of the lubrication system, appearance, temperature, noise, vibration and abnormal phenomena, but also check the ventilation cooling system, sliding friction conditions and the fastening of various components, and carefully check the records.
During monthly or regular inspections, check whether the switch, wiring, grounding device, etc. are loose or not, and if there are any damaged parts, if there are plans and repair measures, check the dust accumulation, clean them in time, check the lead wires and match Whether the line has damage and aging problems. Test the insulation resistance of the motor windings and record.
In addition to the above items, the annual inspection contents should also be disassembled to perform the core check, clean or clean the grease, and check the insulation.
Electrical Encyclopedia: Thermal resistance three-wire system wiring method
Two leads are connected at one end of the thermal resistance sensing element, and one lead is connected to the other end. The form of the lead is called a three-wire system. It can eliminate the influence of the inner lead, and the measurement accuracy is higher than the two-wire system, which is often used in the case where the temperature measurement range is narrow, the wire is too long, or the temperature in the wire wiring is liable to change.
The three-wire lead method is often used in conjunction with the bridge circuit. The two wires are connected to the two bridge arms of the bridge, and the other wire is connected to the power supply of the bridge, eliminating the influence of the lead resistance change. That is, the three-wire lead method can reduce or eliminate measurement errors caused by variations in lead resistance.
In production, thermal resistance temperature meters are mostly measured with an unbalanced bridge. The measuring circuit principle is as shown in Figure 1. Since the resistance value of the copper wire connecting the thermal resistor to the bridge changes with the change of the ambient temperature, if only the connecting wire is connected to a bridge arm, when the ambient temperature changes When connecting the wire resistance.
The change value will be superimposed with the resistance change value of the RTD, resulting in an additional error. Therefore, in the industry, the three-wire wiring method is generally adopted, and the wires 2 and 3 are respectively connected to the two bridge arms of the bridge, when the resistance of the wires changes. Can offset each other to reduce the impact on the value of the instrument. However, the error reduction is limited. For an unbalanced bridge, full compensation can only be obtained at the beginning of the meter scale, and the above additional error is maximum at full scale.
For the unbalanced bridge, the additional temperature error of the power supply lead should also be considered. When there is a current flowing through the superheat resistor to connect the power supply wire 1, there will be a certain voltage drop. When the ambient temperature changes, the upper and lower branch voltages of the bridge It will also change, which will bring some additional temperature error to the meter.
The three-wire wiring method must be used in conjunction with the corresponding wire-made RTD components to achieve true three-wire wiring. However, in reality, many manufacturers use thermal resistance, and most of the thermal resistance components in the protection tube have only two leads, that is, the thermal resistance component is two-wire, although three connection wires are used from the protection tube junction box to the display instrument. But this can only be regarded as a two-wire thermal resistance wiring method, or a three-wire thermal resistance two-wire wiring method.
Pressure Gauges,Door Pressure Gauge,Differential Pressure Gauge,Stainless Steel Manometer
ZHOUSHAN JIAERLING METER CO.,LTD , https://www.zsjrlmeter.com