page 147, for information about setting this parameter higher then the maximum Heavy Duty current rating.) The motor rated current is used in the following:

•

Current limits (see section 8.3 Current limits on page 147, for more information)

•

Motor thermal overload protection (see section 8.4 Motor thermal protection on page 147, for more information)

•

Vector mode voltage control (see Voltage mode Pr 0.07, later in this table)

•

Slip compensation (see Slip compensation Pr 5.27, later in this table)

•

Dynamic V/F control

Pr 0.44 {5.09} Motor rated voltage

Pr 0.47 {5.06} Motor rated frequency

The motor rated voltage Pr 0.44 and the motor rated frequency Pr 0.47

are used to define the voltage to frequency characteristic applied to the

motor (see voltage mode Pr 0.07, later in this table). The motor rated

frequency is also used in conjunction with the motor rated speed to

calculate the rated slip for slip compensation (see motor rated speed

Pr 0.45, later in this table).

Pr 0.45 {5.08} Motor rated speed

Pr 0.42 {5.11} Motor number of poles

The motor rated speed and the number of poles are used with the motor rated frequency to calculate the rated slip of induction machines in Hz.

Rated slip (Hz) = Motor rated frequency - (Number of pole pairs x [Motor rated speed / 60]) =

If Pr 0.45 is set to 0 or to synchronous speed, slip compensation is disabled. If slip compensation is required this parameter should be set to the

nameplate value, which should give the correct rpm for a hot machine. Sometimes it will be necessary to adjust this when the drive is commissioned

because the nameplate value may be inaccurate. Slip compensation will operate correctly both below base speed and within the field-weakening

region. Slip compensation is normally used to correct for the motor speed to prevent speed variation with load. The rated load rpm can be set higher

than synchronous speed to deliberately introduce speed droop. This can be useful to aid load sharing with mechanically coupled motors.

Pr 0.42 is also used in the calculation of the motor speed display by the drive for a given output frequency. When Pr 0.42 is set to 'Auto', the number

of motor poles is automatically calculated from the rated frequency Pr 0.47, and the motor rated speed Pr 0.45.

Number of poles = 120 x (Motor rated frequency Pr 0.47 / Motor rated speed Pr 0.45) rounded to the nearest even number

Pr 0.43 {5.10} Motor rated power factor

The power factor is the true power factor of the motor, i.e. the angle between the motor voltage and current. The power factor is used in conjunction

with the motor rated current Pr 0.46, to calculate the rated active current and magnetising current of the motor. The rated active current is used

extensively to control the drive, and the magnetising current is used in vector mode stator resistance compensation. It is important that this

parameter is set up correctly. The drive can measure the motor rated power factor by performing a rotating autotune (see Autotune Pr 0.40, below).

Pr 0.40 {5.12} Autotune

There are two autotune tests available in open loop mode, a stationary and a rotating test. A rotating autotune should be used whenever possible so

the measured value of power factor of the motor is used by the drive.

•

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 test

measures the stator resistance (Pr 5.17) and voltage offset (Pr 5.23), which are required for good performance in vector control modes (see

Voltage mode Pr 0.07, later in this table). The stationary autotune does not measure the power factor of the motor so the value on the motor

nameplate must be entered into Pr 0.43. To perform a Stationary autotune, set Pr 0.40 to 1, and provide the drive with both an enable signal (on

terminal 31) and a run signal (on terminal 26 or 27).

•

A rotating autotune should only be used if the motor is unloaded. A rotating autotune first performs a stationary autotune, as above, before rotating the

motor at

base speed in the direction selected for several seconds (regardless of the speed reference). In addition to the stator resistance (Pr 5.17)

and voltage offset (Pr 5.23), the rotating autotune measures the power factor of the motor and updates Pr 0.43 with the correct value. To perform a

Rotating autotune, set Pr 0.40 to 2, and provide the drive with both an enable signal (on terminal 31) and a run signal (on terminal 26 or 27).

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 31, setting the drive enable parameter Pr 6.15 to OFF (0) or disabling the drive via the control word (Pr 6.42 &

Pr 6.43).

Unidrive SP User Guide

Issue Number: 13

Electrical

Getting