1. Input AC power supply overvoltage
In this case, the input voltage exceeds the normal range. Generally, the load is lighter on holidays, the voltage rises or falls, and the line fails. At this time, it is better to disconnect the power supply, check, and process.
2. Power generation overvoltage
The probability of occurrence of this situation is relatively high, mainly because the synchronous speed of the motor is higher than the actual speed, so that the motor is in the power generation state, and the frequency converter has no brake unit installed, and two cases can cause this fault.
(1) When the inverter drags the large inertia load, its deceleration time is set relatively small. During the deceleration process, the speed of the inverter output is relatively fast, while the load is slowed down by the resistance of the load, so that the speed of the load drag motor It is higher than the speed corresponding to the frequency of the inverter output, the motor is in the power generation state, and the inverter has no energy feedback unit, so the voltage of the DC circuit of the inverter tributary rises, exceeds the protection value, and the fault occurs, which often occurs in the paper machine. In the dry part, dealing with such a fault can increase the regenerative braking unit, or modify the inverter parameters to set the inverter deceleration time longer. The function of increasing the regenerative braking unit includes energy consumption type, and talks about DC bus absorption type and energy feedback type. The energy consumption type is in the DC loop of the inverter and talks about a braking resistor. The DC bus voltage is detected to control the on and off of the power tube. And talk about DC bus absorption type used in multi-motor transmission system, this system often has one or several motors often work in the power generation state, generating regenerative energy, which is absorbed by the motor in the electric state through the chat bus. The energy feedback type inverter-side converter is reversible, and the inverter can return the regenerative energy to the grid when regenerative energy is generated.
(2) This fault may also occur when multiple electric actuators are operating the same load, mainly due to no load distribution. Taking two motors to drag a load as an example, when the actual rotational speed of one motor is greater than the synchronous speed of the other motor, the motor with a high rotational speed is equivalent to the prime mover, and the low rotational speed is in a power generating state, causing a malfunction. In the paper machine often occurs in the press section and the net section, and load distribution control is required during processing. It is possible to adjust the characteristics of the inverter in the branch of the paper machine drive speed chain.
The bimetal thermometer combines two metals with different linear expansion coefficients, and one end is fixed. When the temperature changes, the two metals have different thermal expansion, which drives the pointer to deflect to indicate the temperature.
WSS series bimetal thermometer is a kind of field measuring instrument for measuring medium and low temperature. It can directly measure the temperature of liquid, steam and gas medium in the range of - 80 ℃~+500 ℃ in various production processes. It is suitable for temperature measurement when the precision is not high in industry. As a temperature sensing element, bimetallic sheet can also be used for automatic temperature control.
The bimetallic thermometer can be divided into axial, radial, 135 ° and universal types according to the connection direction of the pointer plate of the bimetallic thermometer and the protective tube.
â‘ Axial bimetal thermometer: the pointer plate is vertically connected with the protective tube.
â‘¡ Radial bimetal thermometer: the pointer plate is connected with the protective tube in parallel.
③ 135 ° directional bimetal thermometer: the pointer plate is connected with the protective tube at 135 °.
â‘£ Universal bimetal thermometer: the connecting angle between the pointer plate and the protective tube can be adjusted at will.
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