# Brief inverter FAQs（3）

UpdateTime：2013-01-11Clicks：1323Word Size：T|T
1, the so-called open loop is what mean?
The motor device to use a speed detector (PG), the actual speed feedback to the control device to control, known as the "closed loop", need not PG operation is called "open loop". General inverter is open-loop way more, also some models using option for PG feedback. Closed-loop control without speed sensor is according to the established mathematical model according to the actual flux of the motor speed, equivalent to with a virtual speed sensor to form closed-loop control.
2, the actual speed for a given speed have deviation when how to do?
Open loop, frequency converter, even if output for a given frequency, the motor in the load running, the motor speed in the range of rated slip (1% ~ 5%). For speed control precision is high, even if the load changes required to approximate to the given speed running, which has the function of PG feedback frequency converter can be used (optional part).
3, if use motor with PG, speed accuracy can improve after feedback?
Frequency converter with PG feedback functions, accuracy is improved. But the speed accuracy value is determined by the accuracy of the PG and the resolution of the inverter output frequency.
4, stall prevention function is what mean?
If the given acceleration time too short, the output of the inverter frequency changes than speed angular frequency (electricity), the inverter will be tripped by through the overcurrent, full stop, this is called stall. In order to prevent continue to stall to make motor running, going to check out the size of the current to frequency control. When speed up slow acceleration rate appropriately when electric current is too large. Slow down. A combination of up to stall.
5, with acceleration time and deceleration time could be given models respectively, and the deceleration time given models together, what's the point?
Deceleration can be given models, respectively, for a short time haste and slow slow, or for small machine tools need to strict the occasion of a given production takt time is appropriate, but for the occasions, such as fan transmission deceleration time is longer, acceleration and deceleration time can be given.
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