The I2t protection (motor I2t protection) prevents motor damage due to long over-current operation. In order to set this protection, you need to select a point on the I2t motor thermal protection curve, and then input the I2t over-current value and the I2t time in the Drive Setup dialog. These points, together with the nominal motor current In, define the surface SI2t (see below).
If the motor's instantaneous current is higher than the nominal current of the motor, the difference between the square of the instantaneous current and the square of the nominal current is integrated and compared to the SI2t value (see figure below). When the integral equals the SI2t surface, the I2t protection is triggered.
With other words, when the current through the motor exceeds the nominal current, the drives starts to calculate, at each current loop (fast loop), the difference between the square of the instantaneous current and the square of the nominal current. The value obtained at the current step is added to the value obtained at the previous step, and so on. When the sum is equal or greater than the SI2t surface from the first picture, the drive I2t protection is triggered.
For example, if the nominal current of the motor is 2 A and the I2t protection is set to 3 A for 10 s, the SI2t will be (3^2 -2^2) x 10 = 50 [A^2s]. So, when the sum presented above is equal or greater than 60, the drive I2t protection is triggered.
The I2T protection value can be set from the Drive Setup dialog.
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