外文翻译--基于plc的异步电动机运行监控系统的设计与实施(编辑修改稿)

外文翻译--基于plc的异步电动机运行监控系统的设计与实施(编辑修改稿)内容摘要：

tput states are stored in fixed memory locations (output image memory Q). The output values held in memory are then used to set and reset the physical outputs of the PLC simultaneously at the end of the program scan. For the given PLC, the time taken to plete one cycle or the scan time is 0, 18 ms/K (for 1000 steps) and with a maximum program capacity of 1000 steps. 外文翻译（原文） 9 The development system prises a host puter (PC) connected via an RS232 port to the target PLC. The host puter provides the software environment to perform file editing, storage, printing, and program operation monitoring. The process of developing the program to run on the PLC consists of: using an editor to draw the source ladder program, converting the source program to binary object code which will run on the PLC’s microprocessor and downloading the object code from the PC to the PLC system via the serial munication port. The PLC system is online when it is in active control of the machine and monitors any data to check for correct operation. A. PLC Speed Control Software In Fig. 4, the flowchart of the speed control software is illustrated. The software regulates the speed and monitors the constant speed control regardless of torque variation. The inverter being the power supply for the motor executes this while, at the same time, it is controlled by PLC’s software. The inverter alone cannot keep the speed constant without the control loop with feedback and PLC. From the control panel, the operator selects the speed setpoint spn and the forward/backward direction of rotation. Then, by pushing the manual start pushbutton, the motor begins the rotation. If the stop button is pushed, then the rotation stops. 外文翻译（原文） 10 Fig. 4. Flowchart of speed control software. The AIM receives the trip signal sI from the stator current sensor, the speed feedback signal from the tachogenerator, and the spn signal from the control panel. In this way, the PLC reads the requested speed and the actual speed of the motor. The difference between the requested speed by the operator and the actual speed of the motor gives the error signal. If the error signal is not zero, but positive or negative, then the PLC according to the putations carried out by the CPU decreases or increases the V/f of the inverter and, as a result, the speed of the motor is corrected. Fig. 5 Flowchart of monitor and protection software The implemented control is of proportional and integral (PI) type (., the error signal is multiplied by gain PK , integrated, and added to the requested speed). As a result, the control signal is sent to the DOM and connected to the digital input of the 外文翻译（原文） 11 inverter to control V/f variations. At the beginning, the operator selects the gain PK by using a rotary resistor mounted on the control panel (gain adjust) and the AIM receives its voltage drop as controller gain signal (0 –10 V). The requested speed spn is selected using a rotary resistor and the AIM reads this signal. Its value is sent to the AOM and displayed at the control panel (speed set point display). Another display of the control panel shows the actual speed puted from the speed feedback signal. A third display shows the load torque puted from the load current signal in Newtonmeters (N m). Their corresponding signals are output to the AOM (Table IV). During motor operation, it is not possible to reverse its direction of rotation by changing the switch position. Before direction reversal, the stop button must be pushed. For motor protection against overloading currents during starting and loading, the following mands were programmed into the software. i) Forward/backward signal is input to DIM. ii) Speed setpoint signal spn , the load current LI , the stator current SI , and the speed feedback signal are input to AIM. iii) At no load  , if the speed set point is lower than 20% or spn 300 r/min, the motor will not start. vi) In all other situations, the motor enters in the speed control mode and the speed control software is executed as described in Subsection A. C. Cutoff and Restart Motor Software In Fig. 6, the flowchart of this software is shown. • In overloading situations, the motor is cut off and the trip lamp (yellow) is lit. The operator must release the thermal relays and then must turn off the trip lamp by pushing trip or stop button. The thermal relays are set to the motor rated current A. 外文翻译（原文） 12 Following this, the motor can be started again. • The motor can be cut off by the operator pushing the stop button: the display of the actual speed is set to zero, the start lamp (green) turns off, and the stop lamp (red) turns on and remains lit for 3s. • The load must be disconnected immediately after the motor cuts off and before the drive system is restarted. The motor will not start before 3s after cut off even if the start button is pushed. VI. RESULTS The system was tested during operation with varying loads including tests on induction motor speed control performance and tests for trip situations. The PLC monitors the motor operation and correlates the parameters according to the software. At the beginning, for reference purposes, the performance of induction motor supplied from a standard 380 V, 50Hz work was measured. Then, the experimental control system was operated between no load and full load ( N m) in the two different modes described in Section III: a) induction motor fed by the inverter and with PLC control。 b) induction motor fed by the inverter. The range of load torque and of speed corresponds to the design of the PLC hardware and software as described in the previous sections. The speed versus to。