Siemens MICROMASTER Vector Operating Instructions Manual page 37

5. OPERATING MODES
In many cases, when default factory parameters are used, the default stator resistance set in P089 will generally suit the default power
rating set in P085. Should the inverter and motor ratings differ, an automatic Stator Resistance calibration should be performed by
setting P088 =1. Continuous Boost (P078) and Starting Boost (P079) are dependent on the value of Stator Resistance - too high a
value may cause overcurrent trips or motor overheating.
5.3.2 Flux Current Control (FCC) Operation (P077 = 1)
Flux Current Control operates by monitoring and maintaining the motor flux current continuously. This ensures that the best
performance and efficiency are obtained. FCC is not as complex as SVC, and therefore is easier to set up and operate.
Note: This mode can result in reduced power consumption.
5.3.3 Sensorless Vector Control (SVC) Operation (P077 = 3)
When SVC operating mode is selected (P077=3), the inverter uses an internal mathematical model of the motor, together with accurate
current sensing, to calculate the position and speed of the rotor. It is therefore able to optimise the applied voltage and frequency to the
motor to give improved performance.
Setpoint
Input
Figure 5.3.3 : MICROMASTER Vector sensorless Vector operation
Although there is no position or speed feedback from the motor, the control system is a closed loop system because it compares the
internal motor model performance with the desired performance. The system must therefore be carefully set up and stabilised for best
performance.
Setting up SVC Operation
1. Set the correct Motor parameter settings in Parameters P080 to P085.
2. Select Sensorless Vector Operating mode P077 = 3
3. Ensure that the motor is cold and apply a run command. The display will show CAL to indicate that it is measuring the motor stator
resistance. After a few seconds the motor will run. Calibration only occurs the first time that a run command is given following P077
being set to 3. It can be forced by changing P077 from SVC operation and back again, or by selecting P088 =1 (Stator Resistance
Calibration). Interrupting the calibration process by disconnecting the power or removing the run command may give erroneous
results and calibration should be repeated. If motor parameters are changed recalibration is also recommended.
Like any control system, SVC must be stabilised by setting the Gain (P386) and Integral (P387) terms. Actual values and setting
4.
up is determined by testing, but the following procedure is suggested:
Whilst the inverter is operating under typical conditions, increase the value of P386, the loop gain, until the first
signs of speed instability occur. The setting should then be reduced slightly (approx. 10%) until stability is restored.
As a guide, the optimum setting required will be proportional to the load inertia.
© Siemens plc 1999
P, I,
Processor
(P386, P387)
Error
Motor Model Speed, Position and Torque feedback
Output to Motor
Internal Motor
Model
37
English
G85139-H1751-U529-D1
4/8/99