Motor Torque vs Current     

Before the drive inverter can be selected, the motor torque requirements must be converted to inverter current requirements.  The Motor Torque vs Current chart below illustrates the torque-to-current conversion model.

Note: For an asynchronous induction motor, or a permanent magnet motor operating in field weakening mode, the chart provides the option to display either the stator phase current, IPh, or the torque producing current, Iq. When no option is provided, the torque producing current, Iq, is displayed.

The motor torque vs current calculation is a non-linear exponential overload model, and makes adjustments for speed dependent losses, bearing friction and motor temperature, among other factors.

Specify the motor speed in the speed input field above the chart, and the torque-to-current model is updated for the given speed.
 

Linear assumption based on the motor torque constant, kto.  This is shown for reference, and to illustrate the considerable error made when assuming kt is linear throughout the entire motor torque range.
 

Illustrates the available motor torque given the inverter peak current rating
 

 

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