1. What does it mean to open a ring?
A speed detector (PG) is provided for the motor device to be used, and the actual speed is fed back to the control device for control, which is called "closed loop". If the PG is not operated, it is called "open loop".
2. What should I do if the actual speed is different for a given speed?
When the ring is open, even if the inverter outputs a given frequency, the motor's speed will fluctuate within the range of rated slip (1%~5%) when the motor is running with load. For the requirement that the speed regulation accuracy is relatively high, even if the load is changed, it is required to operate at a speed close to a given speed, and an inverter (optional) having a PG feedback function can be used.