There are three autotune tests available in RFC-A mode, a stationary test, a rotating test and an inertia measurement test. A stationary autotune will

give moderate performance whereas a rotating autotune will give improved performance as it measures the actual values of the motor parameters

required by the drive. An inertia measurement test should be performed separately to a stationary or rotating autotune.

It is highly recommended that a rotating autotune is performed (Pr 00.040 set to 2).

•

A stationary autotune can be used when the motor is loaded and it is not possible to remove the load from the motor shaft. The stationary

autotune measures the Stator Resistance (05.017) and Transient Inductance (05.024) of the motor. These are used to calculate the current loop

gains, and at the end of the test the values in Pr 04.013 and Pr 04.014 are updated. Maximum Deadtime Compensation (05.059) and Current At

Maximum Deadtime Compensation (05.060) for the drive are also measured. Additionally, if Enable Stator Compensation (05.049) = 1, then

Stator Base Temperature (05.048) is made equal to Stator Temperature (05.046). A stationary autotune does not measure the power factor of

the motor so the value on the motor nameplate must be entered into Pr 00.043. To perform a stationary autotune, set Pr 00.040 to 1, and

provide the drive with both an enable signal (on terminal 29) and a run signal (on terminal 24).

•

A rotating autotune should only be used if the motor is unloaded. A rotating autotune first performs a stationary autotune, a rotating test is then

performed in which the motor is accelerated with currently selected ramps up to a frequency of Rated Frequency (05.006) x 2/3, and the

frequency is maintained at the level for up to 40 s. During the rotating autotune the Stator Inductance (05.025), and the motor saturation

breakpoints (Pr 05.029, Pr 05.030, Pr 06.062 and Pr 05.063) are modified by the drive. The power factor is also modified for user information

only, but is not used after this point as the stator inductance is used in the vector control algorithm instead. To perform a Rotating autotune, set

Pr 00.040 to 2, and provide the drive with both an enable signal (on terminal 29) and a run signal (on terminal 24).

•

The inertia measurement test can measure the total inertia of the load and the motor. This is used to set the speed loop gains (see Speed loop

gains) and to provide torque feed-forwards when required during acceleration.

Applied torque (sensorless mode) This test may give inaccurate results, if the motor rated speed is not set to the correct value for the motor,

or if standard ramp mode is active. During the inertia measurement test a series of progressively larger torque levels are applied to the motor

(20 %, 40 % ... 100 % of rated torque) to accelerate the motor up to

deceleration time. The test attempts to reach the required speed within 5 s, but if this fails the next torque level is used. When 100 % torque is

used the test allows 60 s for the required speed to be reached, but if this is unsucessful an Autotune trip is initiated. To reduce the time taken for

the test it is possible to define the level of torque to be used for the test by setting Mechanical Load Test Level (05.021) to a non-zero value.

When the test level is defined the test is only carried out at the defined test level and 60 s is allowed for the motor to reach the required speed.

It should be noted that if the maximum speed allows for flux weakening then it may not be possible to achieve the required torque level to

accelerate the motor quickly enough. If this is the case, the maximum speed reference should be reduced. To perform an Inertia measurement

autotune, set Pr 00.040 to 4, and provide the drive with both an enable signal (on terminal 29) and a run signal (on terminal 24).

Following the completion of an autotune test the drive will go into the inhibit state. The drive must be placed into a controlled disable condition

before the drive can be made to run at the required reference. The drive can be put in to a controlled disable condition by removing the Safe Torque

Off signal from terminal 29, setting the Drive Enable (06.015) to OFF (0) or disabling the drive via the control word (Pr 06.042 & Pr 06.043)

Pr 00.038 {04.013} / Pr 00.039 {04.014} Current Loop Gains

The current loop gains proportional (Kp) and integral (Ki) gains control the response of the current loop to a change in current (torque) demand. The

default values give satisfactory operation with most motors. However, for optimal performance in dynamic applications it may be necessary to

change the gains to improve the performance. The Current Controller Kp Gain (04.013) is the most critical value in controlling the performance. The

values for the current loop gains can be calculated by performing a stationary or rotating autotune (see Autotune Pr 00.040, earlier in this table) the

drive measures the Stator Resistance (05.017) and Transient Inductance (05.024) of the motor and calculates the current loop gains.

This will give a step response with minimum overshoot after a step change of current reference. The proportional gain can be increased by a factor

of 1.5 giving a similar increase in bandwidth; however, this gives a step response with approximately 12.5 % overshoot. The equation for the integral

gain gives a conservative value. In some applications where it is necessary for the reference frame used by the drive to dynamically follow the flux

very closely (i.e. high speed Sensorless RFC-A induction motor applications) the integral gain may need to have a significantly higher value.

Powerdrive F300 User Guide

Issue Number: 2

Electrical

Getting

Basic

installation

started