AKD User Guide | 8 Configuring Motor Settings
8.7 Calculations
WorkBench uses the following equations to calculate parameter values.
8.7.1 Current Loop
The current loop proportional gain (IL.KP) must be such that the current loop closed loop crossover frequen-
cy/bandwidth (BW) nominal is the lesser of 2000 Hz or (PWM Frequency/4).
Then, with this frequency:
IL.KP = 2*π*(desired bandwidth in Hz)*(motor L line-line in H)
Setting the D and Q components
8.7.2 Velocity Loop
VL.KP = (2*π*75)*(2*Jm/Kt) = 300*PI*Jm/Kt
VL.KI = 5
8.7.3 Position Loop
PL.KP = ??
8.7.4 Slider Tuning
The slider tuning algorithm in WorkBench currently uses the following algorithm.
8.7.4.1 Input - Motor Data
The values for inertia, Jm (Kg / cm2), and torque constant, Kt (Nm/A), are obtained from either the SFD or the
motor model number that you select.
8.7.4.2 Constants
Velocity Loop Bandwidth – BW = The default value is 75Hz.
Input - Inertia Ratio – Q = The default is 1.
8.7.4.3 Output - Control Loop Gains
VL.KP = 2 * π * BW * Jm * (1+Q) * 0.0001/Kt
VL.KPI = BW*0.08 -1 (minimum of 1)
PL.KP = BW/5
8.8 Foldback
Thefoldback featurein theAKD protects boththemotorandthedrive from overheating. Twocurrent foldback algo-
rithms runinparallelinthedrive: thedrivefoldback algorithmandthe motorfoldback algorithm. Eachalgorithmuses
different sets of parameters. Eachalgorithm has its ownfoldback current limit, IL.DIFOLD (drive foldback)andIL.M-
IFOLD (motorfoldback). The overall foldback current limit is theminimum of thetwoat any givenmoment.
IL.IFOLD = min (IL.DIFOLD, IL.MIFOLD).
72 Kollmorgen | December 2010
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