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Menu 5
Commander SK Advanced User Guide 75
Issue Number: 9 www.controltechniques.com
The motor rated frequency and the motor rated voltage (Pr 5.09) are used to define the voltage to frequency characteristic applied to the drive (see
Pr 5.09). The motor rated frequency is also used in conjunction with the motor full load rpm to calculate the rated slip for slip compensation (see
Pr 5.08).
The motor rated current should be set at the machine nameplate value for rated current.
This value is used in the following:
Current limit, see Pr 4.07 on page 65
Motor protection system, see Pr 4.15 on page 68
Slip compensation, see Pr 5.08
Vector mode voltage control, see Pr 5.09 on page 76
Dynamic V to f control, see Pr 5.13 on page 78
The rated full load rpm is used with the motor rated frequency and No. of motor poles to calculate the rated slip of the induction machine in Hz.
The rated slip is used to calculate the frequency adjustment required to compensate for slip from the following equation:
If slip compensation is required, Pr 5.27 must be set to On(1) and 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 rated 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.
If Pr 5.08 is set to 0 or to synchronous speed, slip compensation is disabled.
If the full load speed of the motor is above 9999rpm, slip compensation should be disabled. This is because a value above 9999 cannot be entered in
Pr 5.08. It may be useful to disable slip compensation when using the Commander SK on a high inertia load e.g. fan or high speed spindle motor.
5.06 Motor rated frequency {39}
Coding
Bit SP FI DE Txt VM DP ND RA NC NV PT US RW BU PS
1 111
Range 0.0 to 550 Hz
Default Eur: 50.0, USA 60.0
Second motor
parameter
Pr 21.06
Update rate Background
5.07 Motor rated current {06}
Coding
Bit SP FI DE Txt VM DP ND RA NC NV PT US RW BU PS
12 1 111
Range 0 to RATED_CURRENT_MAX A
Default Drive rated current (Pr 11.32)
Second motor
parameter
Pr 21.07
Update rate Background
5.08 Motor rated full load rpm {07}
Coding
Bit SP FI DE Txt VM DP ND RA NC NV PT US RW BU PS
111
Range 0 to 9999 rpm
Default Eur: 1500, USA 1800
Second motor
parameter
Pr 21.08
Update rate Background
Rated slip Motor rated frequency No. of motor pole pairs Motor full load rpm 60⁄×()– Pr 5.06 Pr 5.11 2⁄()Pr 5.08 60⁄()×[]–= =
Slip compensation Rated slip Active current Rated active current⁄×=
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