No, the inverter with fixed frequency has output voltage, and the motor input has a large current, which causes the protection of inverter.
The inverter can be installed on the wall or in a cabinet, so as not to reduce the heat dissipation effect of the inverter, please install it vertically.
For a digital control inverter, even if the frequency command is ananalog signal, the output frequency is also given reference level. The smallestunit of this differential is known as the frequency conversion reAnswer. Thefrequency reAnswer is usually 0.015~0.5Hz. For example, the reAnswer is 0.5 Hz,so the top of 23Hz can be changed to 23.5 and 24.0 Hz, so the motor's action isalso followed by the level. This creates problems for the use of continuousvolume control. In this case, if the reAnswer is 0.015 Hz, the level of grade 4motor is 1r/min, and it can be fully adjusted. In addition, the given reAnswerand output reAnswer are not the same.
When the motor is in operation, if the instruction frequency is decreased, then the motor becomes an asynchronous generator state and works as a brake, which is called regenerative (electrical) braking.
If the given acceleration time is too short, the output of theinverter frequency changes more than speed change of the angular frequency (electricity),the inverter will trip due to flowing through the overcurrent, and operationwill stop, this is called stall. To prevent the motor from running, check thefrequency control of the current. Speed up when the acceleration current is toolarge. The same is true with deceleration. The combination of the two is thestall function.
The inverter with PG feedback can improve the accuracy. However, the value of the speed precision depends on the accuracy of the PG itself and the frequency of the inverter output.
During open loop, the inverter can change the speed of the motor atthe range of rated slip (1% ~ 5%) even when the motor is running with load. Forthe requirement of high speed regulation accuracy, even if the load change isrequired to operate at a given speed, the inverter with PG feedback can beused.
In engineering practice, themost widely used regulator control law is proportional, integral, differentialcontrol, or PID control, and PID control.
Theparameter setting of PID controller is the core content of control systemdesign. It is based on the characteristics of the controlled process to determinethe ratio of PID controller, the integral time and the size of the differentialtime. There are many methods of PID controller parameter setting, and thecritical ratio method is generally adopted. The whole procedure of PIDcontroller parameters by using this method is as follows:
(1) First select a sampling cycle short enough to let the system work
(2) Only add the proportional control link, until the system has a criticaloscillation of the input step response, and record the proportional amplificationcoefficient and the critical oscillation period
(3) The parameters of PID controller are calculated byformula under certain degree of control.
The electrical device used to set speed detector (PG) to feedback the actual speed to control device, such process is known as the "closed loop", the one needs no PG operation is called "open loop". General inverter is mostly open-loop, some models also use optionals for PG feedback. Speed sensorless closed-loop control method is based on the established mathematical model according to the actual flux of the motor speed, the equivalent of with a virtual speed sensor to form closed-loop control.
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