Nidec Digitax HD M753 EtherCAT User Manual Download Page 82

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Digitax HD M753 Control User Guide

Issue Number: 3

8.1.3

Open loop motor control

Pr 00.046 {05.007}

Rated Current

Defines the maximum continuous motor current

The motor rated current parameter must be set to the maximum continuous current of the motor. The motor rated current is used in the following:
•

Current limits (see section 8.2

Current limits

on page 92, for more information)

•

Motor thermal overload protection (see section 8.3

Motor thermal protection

on page 92, for more information)

•

Vector mode voltage control (see

Open Loop Control Mode

(00.007), later in this table)

•

Slip compensation (see

Enable Slip Compensation

(05.027), later in this table)

•

Dynamic V/F control

Pr 00.044 {05.009}

Rated Voltage

Defines the voltage applied to the motor at rated frequency

Pr 00.047 {05.006}

Rated Frequency

Defines the frequency at which rated voltage is applied

The

Rated Voltage

(00.044) and the

Rated Frequency

(00.047) are used to

define the voltage to frequency characteristic applied to the motor (see

Open

Loop Control Mode

(00.007), later in this table). The

Rated Frequency

(00.047) is also used in conjunction with the motor rated speed to calculate
the rated slip for slip compensation (see

Rated Speed

(00.045), later in this

table).

Pr 00.045 {05.008}

Rated Speed

Defines the full load rated speed of the motor

Pr 00.042 {05.011}

Number Of Motor Poles

Defines the number of motor 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

00.045

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

00.042

is also used in the calculation of the motor speed display by the drive for a given output frequency. When Pr

00.042

is set to ‘Automatic’, the

number of motor poles is automatically calculated from the rated frequency Pr

00.047

, and the motor rated speed Pr

00.045

Number of poles = 120 x (

Rated Frequency

(00.047) /

Rated Speed

(00.045)) rounded to the nearest even number.

Pr 00.043 {05.010}

Rated Power Factor

Defines the angle between the motor voltage and current

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

Rated Current

(00.046), 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 00.040), overleaf).

Pr 00.040 {05.012}

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

(05.017),

Transient Inductance

(05.024),

Maximum Deadtime Compensation

(05.059) and

Current At Maximum Deadtime

Compensation

(05.060) which are required for good performance in vector control modes (see

Open Loop Control Mode

(00.007), 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

00.043

. To perform a

Stationary autotune, set Pr

00.040

to 1, and provide the drive with both an enable signal (terminal 2 & 6) and a run signal (terminal 11 or 13).

•

A rotating autotune should only be used if the motor is unloaded. A rotating autotune first performs a stationary autotune, as above, then a rotating test is
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 that level for 4 seconds.

Stator Inductance

(05.025) is measured and this value is used in conjunction with other motor parameters to

calculate

Rated Power Factor

(05.010). To perform a Rotating autotune, set Pr

00.040

to 2, and provide the drive with both an enable signal (terminal 2 &

6) and a run signal (terminal 11 or 13).

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 2
& 6, setting the

Drive Enable

(06.015) to OFF (0) or disabling the drive via the

Control Word

(06.042) and

Control Word Enable

(06.043).

Output
voltage

/ 2

00.044

/ 2

00.047

Output