29. Since the dead zone is actually a non-working zone, the higher the carrier frequency is, the greater the accumulated value of the dead zone in each cycle will be, and the average value of the output voltage of the inverter will become smaller, so that under the same torque, the frequency conversion The higher the current value of the device.
30. If the carrier frequency is 5KHZ, in the cycle of 50HZ, there will be 100 voltage modulation waves, and the inverter tube will be turned on alternately twice in each cycle, so there will be 200 times of alternate turn-on, just press the dead zone. If the time is 4us to calculate, then the dead zone accumulation time is 800us, then the output value of the voltage is reduced by 4%, 380*96%=364, and the voltage becomes lower. If the dead time is reduced to 2KHZ, then there will only be 80 alternate turn-on times, then the output value of the voltage will be reduced by 1.6%, 380*98.4=374, which is closer to the rated voltage.
31. What is four-quadrant operation? In the first quadrant, the speed, power, and torque are all positive, that is, forward running. In the second quadrant, the speed is positive, the torque is reverse, and the power is negative. This is Forward braking. In the third quadrant, the speed, power, and torque are all reversed, that is, reverse operation. In the fourth quadrant, the speed is reversed, the torque magnetic field is positive, and the power is negative, which is reverse braking.
32. Use the computer instead of the touch screen to communicate with the PLC, and modify the port number in the serial device to be consistent with the port number monitored by the data line. At this time, the simulation download is performed to test the communication.
- 33.In the communication data, read-only, write-only, read-write, three data should be paid attention to. In the touch screen program, do not assign the value in the device channel, which will affect the corresponding data value in the PLC device.
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