1. The servo system controls the motor speed using a speed loop.
2. For DC motors, the speed is determined by the voltage level, while for AC motors, it's determined by the frequency.
3. Therefore, the output from the speed loop regulator controls either the frequency of the AC motor or the voltage of the DC motor.
4. How does the speed loop detect the motor speed? It relies on an encoder for feedback.
5. The encoder’s feedback pulse frequency equals the encoder resolution multiplied by the motor speed.
6. This means that the motor speed is directly proportional to the frequency of the encoder's feedback pulses.
7. In other words, the speed loop uses the frequency of the encoder pulses as its feedback signal.
8. To set the motor speed, the frequency of the encoder pulses must be specified.
9. Once the encoder pulse frequency is known, the motor speed is effectively defined.
10. However, the operation panel doesn’t allow direct setting of the encoder pulse frequency. Instead, it only allows setting the command pulse frequency, which is referred to as S1 in some systems.
11. The electronic gear ratio is calculated as the encoder resolution divided by the number of command pulses per revolution.
12. Therefore, the number of command pulses per revolution equals the encoder resolution divided by the electronic gear ratio.
13. The command pulse frequency is equal to the number of command pulses per revolution multiplied by the motor speed.
14. Since the encoder pulse frequency is also equal to the encoder resolution multiplied by the motor speed, we can derive that:
Command Pulse Frequency = Encoder Pulse Frequency / Electronic Gear Ratio
15. So, by setting the command pulse frequency, you are effectively setting the encoder pulse frequency, which corresponds to the motor speed in the speed loop.
16. Based on this logic, the user only needs to set the command pulse frequency S1 on the operation panel to control the motor speed in the speed loop.
17. This approach does not require changing the pulse equivalent, the electronic gear ratio, or the number of command pulses already configured.
18. The upper limit of the command pulse frequency is typically the rated technical frequency of the position loop counter or the nominal frequency of the PLC pulse.
19. As a result, the upper limit of the command pulse frequency corresponds directly to the maximum motor speed.
20. To determine the command pulse frequency, you can use the formula:
Command Pulse Frequency = Number of Command Pulses per Revolution × Motor Speed (in revolutions per second)
21. With the motor speed known in revolutions per second, the command pulse frequency can be easily calculated.
22. This method ensures precise control over motor speed and provides a clear link between the command signal and the actual motor performance.
23. Understanding this relationship helps users configure the system more effectively and achieve the desired motor behavior.
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