Beijer Electronics AN-BEI-P2-050 - Manual (Page 5)

APPLICATION NOTE AN-BEI-P2-050 Date: 15/02/12
AN-BEI-P2-050 Open Loop Permanent Magnet Motor Control 5
Auto-tune is a non-rotational function although some minor rotation of the motor shaft may occur. It is not
necessary to disconnect the motor from the driven load for this function to be completed successfully but the rotor
should not be locked such that motion is prevented.
Step 6: Setting baseline values for speed loop gains.
The Default gains values for the speed controller are generally suited to standard induction motor control. PM
motors generally permit high gains values and faster response / improved performance. The recommended
starting values for PM motor control are:-
P4-03: Speed Controller proportional Gain, Set to Value 50 (%).
P4-04: Speed Controller Integral Time Constant, Set to Value 100 (ms).
These values may need to be adjusted at the end of the process when system performance can be monitored for
effective tuning and improvement.
Step 7: Enter or check of menu 7 motor values.
If auto-tune function (P4-02) was completed then the following values will be measured and entered automatically
by the Beijer Frequency Inverter P2. The measured values can be viewed in the listed parameters for reference.
The motor values can be entered manually direct to the parameters listed below (taken from the manufacturer
data) if required:-
P7-01: Stator Resistance, Phase to Phase – measured between motor terminals.
P7-03: Lsd Phase Inductance, ‘d’ component of armature winding inductance.
P7-04: Lsq Phase Inductance, ‘q’ component of armature winding inductance.
It is generally recommended for optimum performance and ease of set-up that the auto-tune procedure is used to
complete these values.
Step 8: Setting Motor magnetising time.
Parameter P7-12, motor magnetising time, is used to set a time delay between drive output enable and the drive
output being ramped to the set-point speed. This delay is used by the drive to establish magnetising current in the
motor windings and to align orientation of the rotor to a known position. Magnetising current applied is 50% of the
value contained in parameter P1-08.
This function creates a start-up delay, however if insufficient time is provided to magnetise and orientate the rotor
position then start up and operational performance could be affected. Set to minimum value where the rotor can
be seen to successfully align prior to start up:-
P7-12: Motor Magnetising Time.
Step 9: Low Speed Boost Phase.
Low speed operation of a PM motor, below the speed range of approximately 20:1, should generally be avoided.
Low output voltage from the drive at low speeds (caused by V/f ratio and proportional to designed nominal motor
voltage) can create instabilities in the motor control model as the known phase angle of the rotor becomes
gradually more difficult to predict.
Beijer Frequency Inverter P2 provides a boost function that can inject some current into the motor at low speed to
help ensure the rotor alignment is maintained and to allow effective operation of the motor at lower speeds.
To implement some low speed boost run the drive at the effective lowest frequency required by the application
and increase boost levels to provide both required torque and smooth operation.
Boost current is set as a percentage of motor nominal current setting (P1-08). Boost frequency (P7-15) sets the
frequency cut off point above which boost current is no longer applied to the motor. Boost frequency is set as a
percentage of nominal motor frequency (P1-09).
Care should be taken not to cause motor over-heating issues through sustained low speed / high current boost
operation.
Below are some recommended settings:-
Default Boost Setting: P7-14: Boost Current = 0%. P7-15: Boost Frequency = 0%
Low Boost Setting: P7-14: Boost Current = 25%. P7-15: Boost Frequency = 10%
High Boost Setting: P7-14: Boost Current = 50%. P7-15: Boost Frequency = 20%
Beijer Frequency Inverter P2 PM motor configuration is now complete.