Emerson 4401 - Voltage mode select {41}

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Commander SK Advanced User Guide 79

Issue Number: 9 www.controltechniques.com

Else, if |active current| ≥ 0.7 x rated active current

V/f ratio = Normal V/f ratio

Although the V/f ratio varies, the value shown as Pr 5.06 does not vary from that set by the user.

Use to avoid instability on unloaded large motors.

0 Ur S Stator resistance and voltage offset measured on each run signal

The stator resistance (Pr 5.17) and the voltage offset (Pr 5.23) are measured and the parameters for the selected motor map are over-written each

time the drive is given a run signal. This test can only be done with a stationary machine where the flux has decayed to zero. Therefore this mode

should only be used if the machine is guaranteed to be stationary each time the drive is enabled. To prevent the test from being done before the flux

has decayed there is a period of 1 second after the drive has been in the ready state during which the test is not done if the drive is re-started. In this

case, previously measured values are used. The new values of stator resistance and voltage offset are automatically saved to EEPROM.

1 Ur No measurements

The stator resistance and voltage offset are not measured. The user can enter the motor and cabling resistance into the stator resistance parameter.

However this will not include resistance effects within the drive inverter. Therefore if this mode is to be used, it is best to use the auto-tuning stationary

test initially to measure the stator resistance.

2 Fd Fixed boost mode.

Neither the stator resistance nor the voltage offset are used, instead a fixed characteristic with boost applied as defined by Pr 5.15 is used. (see

Pr 5.09 on page 76)

Fixed boost mode should be used for multiple motor applications.

3 Ur A Stator resistance and voltage offset measured at first drive enable

The stator resistance and voltage offset are measured once, the first time the drive is enabled and run. After the test has been completed successfully

the mode is changed to Ur mode. The stator resistance and voltage offset are written to the parameters for the currently selected motor map and

these parameters along with this parameter are saved in the EEPROM.

If the test fails the stator resistance and voltage offset are not updated, the mode is changed to Ur, but no parameters are saved. If the drive is

powered down and back up, the drive will carry out another autotune when the drive is enabled and run.

4 Ur I Stator resistance and voltage offset measured at each power-up and after a drive default

The stator resistance and voltage offset are measured when the drive is first enabled after each power-up and after a drive default. The new values of

stator resistance and voltage offset are automatically saved to EEPROM.

5 SrE Square law characteristic

Neither the stator resistance nor the voltage offset are used, instead a fixed square law characteristic with boost applied as defined by Pr 5.15 is used.

(see Pr 5.09 on page 76)

The voltage boost level used in fixed boost mode and square law mode is defined by this parameter. See Pr 5.09 on page 76.

This voltage boost compensates for the voltage drop arising from the stator resistance.

5.14 Voltage mode select {41}

Coding