(1) The cooperation between the circuit breaker and the circuit breaker should consider the instantaneous trip device action value of the upper circuit breaker, which should be greater than the maximum expected short-circuit current at the outlet end of the lower circuit breaker.
(2) When the short-circuit current is greater than or equal to the setting value of the instantaneous tripper, the current limiting circuit breaker will trip within a few milliseconds, so the circuit breaker should not be used to complete the selective maintenance requirements of the subordinate maintenance appliances.
(3) The circuit breaker with short delay has a short time limit, and its on-off capacity decreases when its time limit is set at the * large delay, therefore, in the selective maintenance circuit, the short-delay on-off capacity of the circuit breaker should meet the requirements.
(4) It should also be considered that the short-circuit delay returnable characteristics of the upper circuit breaker should not intersect with the action characteristic time curve of the lower circuit breaker, and the short-delay characteristic curve and the instantaneous characteristic curve should not intersect.
(5) When the circuit breaker and fuse are used together, the cooperation between the upper and lower levels should be considered, and the ampere-second characteristic curve of the circuit breaker should be compared with the ampere-second characteristic curve of the fuse, so that in the case of short-circuit current, it can have maintenance selectivity.
(6) When the circuit breaker is used for the maintenance of the distribution line, it is advisable to choose the circuit breaker with a long-delay action over-current tripper, and when a single-phase grounding short circuit occurs at the end of the line, the short-circuit current shall not be less than 1.5 of the setting current of the instantaneous or short-delay overcurrent tripper of the circuit breaker
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The working principle of LS PLC module
When LS PLC is put into operation, its operation process is generally divided into three stages, namely input sampling, user program fulfillment and output rewriting. The completion of these three phases is called a scan cycle. Throughout the operation, the PLC's CPU repeatedly performs the performance at a certain scanning speed on ...
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The basic component of the inverter is LS power generation
The inverter is usually divided into 4 parts: the rectifier unit, the high-capacity capacitor, the inverter and the controller.
Rectifier unit: converts alternating current with a fixed operating frequency into direct current.
High Capacitance: Stores converted electrical energy.
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Calculation method of filter capacitance value of inverter
Alternating current can be converted into direct current using rectifier electricity, but in three-phase electricity, this DC voltage or current contains voltage or current ripple with a frequency of six times the frequency of the power supply. In addition, the inverter inverter will also generate ripple voltage or current due to output and carrier frequency, etc., and reverse ...
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The cause of the failure of low-voltage electrical appliances - LS power generation
In the control circuit of low-voltage electrical appliances, there are simple low-voltage components such as: buttons, safe, etc.; There are also slightly messy low-voltage electrical control components, such as circuit breakers, touch devices, time relays, thermal relays and other simple components, which makes it necessary to diagnose and analyze the cause of the problem.
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Variable frequency regenerative braking method - LS generates electricity
1. Energy consumption type
This method is to connect a braking resistor in parallel in the DC circuit of the inverter, and control the on/off of a power tube by detecting the DC bus voltage. When the DC bus voltage rises to about 700V, the power tube is turned on, and the regenerative energy is passed into the resistor.
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Grounding of the secondary side of the voltage transformer and the current transformer - power generation
1. The transformer is grounded twice
It refers to the grounding of the S2 terminal of the current transformer or the ground of the n terminal of the voltage transformer. As long as the single point is grounded, because the transformer is blocked between the second and the first, before grounding, the secondary winding has no potential connection with the ground, after grounding, the transformer ...
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The wiring distance between the motor and the inverter
Burn two new motors in a row! The output current and voltage of the inverter are balanced, the input voltage is balanced, the current is unstable, and the fluctuation is 20%-50%, the inverter is burned off by a short circuit between 35Hz turns, the grid voltage is very stable, 720V, the interval between the motor and the inverter is 120m, and the input and output terminals of the inverter are powered ...
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Fatal failure of LS power terminal block
From the point of view of application, the function that should be reached is: it is necessary to conduct the local area where the touch part should be conducted, and the touch is reliable. If the insulating part should not be conducted, it is necessary to insulate it firmly. There are three common fatal problems in terminal blocks:
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The given way of the inverter - LS generates electricity
Frequency given meaning and given method
The speed of the motor can be changed by changing the output frequency of the inverter. In order to adjust the output frequency of the inverter, the inverter must supply the signal of the changed frequency, which is called the frequency given signal.
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LS power terminal is faulty
From the perspective of application, the function of the terminal block should be achieved: the contact part should be conducted, and the contact should be reliable. The insulating parts should not be conducted, and it is necessary to insulate them firmly. There are three common forms of fatal failure of terminal blocks:
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The function and function of the inverter VFD - LS produces electricity
1. Energy saving
The energy-saving effect of VFD is mainly manifested in the application of fans and water pumps. After the fan and pump load is selected for frequency conversion speed regulation, the power saving rate is 20% - 60%, because the actual power consumption of the fan and pump load is basically proportional to the cubic speed. When users ask for an average ...
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What is the difference between LS inverter and LG inverter?
LS inverter and LG inverter are the same, there is no difference between the two.
LS inverter, the full name of LS AC inverter governor, after supplying a variety of configurations, converts direct current into communication power, and changes the general power supply ...
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Selection of the color of the conductor of the high and low voltage switchgear - LS power production
1 AC three-phase circuit
a) Yellow for phase A, green for phase B, and red for phase C;
b) Light and blue colors for the neutral line or neutral line;
C) Yellow and green two-color wires are used for safety grounding wires.
2 AC circuits connected by twinax wires or stranded wires: red, black ...
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Inverter circuit structure - LS generates electricity
The main circuit is the power replacement part of the power supply for the asynchronous motor, and the main circuit of the inverter can be roughly divided into two categories: the voltage type is to change the DC of the voltage source to the communication of the DC port of the inverter, and the filter is the capacitor. The current type is to change the DC of the current source to the communication ...
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LS power production contactor application
LS touchers are divided into AC touchers (voltage AC) and DC touchers (voltage DC), which are used in electricity, power distribution and consumption. Toucher broadly refers to the electrical appliances that use the current flowing through the coil to generate a magnetic field in industrial electricity, so that the contacts are closed, so as to control the load.
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Introduction to LS Master-K series PLC programming
LS is an electrical equipment company affiliated to LG, kglwin3.62 programming software Chinese version is a professional plc programming software designed to help daily more efficient planning and development software, the software supports the programming and debugging of LG Master-K series and LG MASTER-K series, and provides ...
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The impact of power quality problems on frequency converters - electricity production
(1) Excessive voltage error will increase the loss of electrical equipment, shorten the life, and work abnormally, which will damage the stability of the synchronous operation of the power system, the stability of the voltage and the economic operation of the power grid, and will cause the inverter system to report overvoltage fault or undervoltage fault.
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The working principle of the LS power production module
When the LS power generation module is put into operation, its working process is generally divided into three stages: input sampling, user program fulfillment, and output rewriting. The completion of these three phases is called a scan cycle. During the entire operation, the PLC's CPU repeatedly performs the upper ...
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An integral part of an electrical solid state relay
Solid state relays consist of three parts: the input circuit, the barrier (coupling), and the output circuit.
Input Circuit:
According to the different categories of input voltage, the input circuit can be divided into DC input circuit, communication input circuit and AC-DC ...
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After the contactor is energized, the start button continuously engages and disconnects ?—— LS generates power
What is the reason why the contactor keeps engaging and disconnecting by pressing the start button after the AC contactor is energized?
In my personal opinion, most of the situation is caused by the wrong coil voltage of the replacement AC contactor, or the purchase of ...
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