Schneider Electric 58 TRX Skip Frequency Diagram, Low Speed Run Time Limit, IR Compensation, Gain

f (Hz) SkipFreq.eps

5 Hz

Reference

Skip Frequency

Diagram

09/2003

Altivar® 58 TRX AC Drives

Adjustment Parameters

Skip Frequency

This parameter, also referred to as jump frequency, allows suppression of a critical speed which causes mechanical resonance phenomena. Prolonged operation of the motor within a frequency band of 5 Hz is prohibited. The frequency band is adjustable over the speed range. A representation of this is shown to the left. There are three skip frequency settings.

This function is useful for applications involving light-weight machines, such as bulk product conveyors, with unbalanced motors. It is also useful for applications involving fans and centrifugal pumps.

Low Speed Run Time Limit

This function, also referred to as a sleep function, is used to stop the motor after running at low speed for a programmed amount of time, with the run command present and zero speed reference. The length of run time at low speed is adjustable from 0.1 to 999.9 seconds. The factory setting is 0 s, which disables this function. The motor will re-start if the frequency reference becomes greater than the low speed or the run command is cycled.

This function can be used for automatic starting and stopping of pressure-regulated pumps.

IR Compensation

This parameter is used to adjust low-speed torque for optimal performance. Adjust this parameter to compensate for the resistive voltage drop of the motor stator windings and the conductors connecting the motor and drive controller.

The factory setting is 100%, with a range of 0 to 150%. (If using special motors such as synchronous permanent magnet motors, synchronous wound field motors, or synchronous reluctance motors, the adjustment range can be expanded and is 0 to 800%.)

This parameter is typically used to boost torque performance during low speed operation. If an auto- tune is performed, adjustment of this parameter is usually not required.

Slip Compensation

This parameter is used to adjust the slip compensation to improve speed regulation.The factory setting is 100%, with a range of 0 to 150%.

Induction motors develop torque based on the slip, which is the difference between the speed of the rotating magnetic field in the stator and the speed of the rotor. As the load increases, the slip increases to produce the necessary torque. In applications where the change in speed due to slip is undesirable, the slip compensation should be increased. When this parameter is increased, the drive controller will automatically increase the output frequency. The amount of increase is proportional to the increase of the load, allowing one setting for the entire speed range.

Gain

This parameter allows adjustment of the drive controller’s response time to sudden changes in the motor load. The factory setting is 20%, with a range of 0 to 100%.

Decreasing the gain parameter slows the response time of the drive. Increasing the gain parameter makes the drive respond more quickly. This parameter should be increased when it is not desirable for motor speed to change as the motor load changes, such as in applications that have fast cycle times or high torque requirements.

Stability

This parameter allows adjustment of speed overshoot of the drive controller to sudden changes in the motor load. The factory setting is 20%, with a range of 0 to 100%.

Increasing the stability setting dampens the overshoot. This parameter should be adjusted with the gain setting to tune the drive response to meet desired performance on applications that have fast cycle times or high torque requirements.

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