Siemens SINAMICS S120 Function Manual page 548

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Function modules

9.12 Moment of inertia estimator

Function description

In applications in which the motor runs predominantly at constant speed, the converter can only

rarely calculate the moment of inertia using the "Moment of inertia estimator" (see Chapter

"Moment of inertia estimator (Page 540)"). Moment of inertia precontrol is available for

situations such as these. The moment of inertia precontrol assumes that there is an

approximately linear relationship between the moment of inertia and the load torque.

Configuring the function

Proceed as follows to configure the function:

1. Ensure that the acceleration precontrol scaling is not equal to zero: p1496 ≠ 0.

2. Activate the acceleration model of the speed controller precontrol: p1400.20 = 1.

3. Configure the moment of inertia precontrol using p5310.

Using bit 0, you can activate the calculation of the characteristic (p5312 ... p5315)

Using bit 1, you can activate the moment of inertia precontrol. The following bit combinations

are possible:

The status word of the moment of inertia precontrol is indicated in r5311.

Example: Horizontal conveyors

For a horizontal conveyor, in a first approximation, the moment of inertia depends on the load.

The relationship between load torque M

characteristic.

The following applies in accordance with the respective direction of rotation:

● Positive direction of rotation:

Moment of inertia J = p5312 · load torque M

● Negative direction of rotation:

Moment of inertia J = p5314 · load torque M

p5310.0 = 0, p5310.1 = 0 Moment of inertia precontrol not active

p5310.0 = 0, p5310.1 = 1 Cyclic calculation of the coefficients without moment of inertia precontrol

p5310.0 = 1, p5310.1 = 0 Moment of inertia precontrol activated (without cyclic calculation of the

p5310.0 = 1, p5310.1 = 1 Moment of inertia precontrol activated (with cyclic calculation of the co‐

Relationship between load torque M

(commissioning)

coefficients)

and torque is saved in the converter as linear

Function Manual, 06/2019, 6SL3097-5AB00-0BP2

Drive functions