Siemens SINAMICS S120, Function Manual

Page: 146 / 1094

Servo control
4.12 Encoderless operation
Drive functions
146
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
Commissioning/optimization
1. Estimate the motor current p1612 on the basis of the mechanical conditions (I = M/kt).
2. For synchronous motors with high overload setting (p0640 significantly higher than
p0305), it may be necessary to reduce the current limiting in encoderless operation
(p0642).
3. For a third-party motor, carry out the stationary measurement - and if possible - also the
rotating measurement and accept the determined data (see Chapter "Motor data
identification (Page 149)"). Check the current controller setting.
4. If the total moment of inertia has not already been determined using the rotating
measurement, you have the possibility of determining the total moment of inertia as
follows:
–
If an encoder is being used, and the motor has a restricted traversing path (e.g.
encoderless operation is only used when an encoder develops a fault or only for the
upper speed range):
Determine the moment of inertia using the rotating measurement of the motor data
identification (p1959 = 420 hex (i.e. only commutation angle and Lq characteristic),
p1960 = 1). If you carry out the motor data identification using the STARTER screen,
set p1959, start the measurement and accept the result.
– If the motor can endlessly rotate (with and without encoder)
Determine the moment of inertia using the rotating measurement of the motor data
identification (p1959 = 404 hex (i.e. only commutation angle and moment of inertia),
p1960 = 1). If you carry out the motor data identification using the STARTER screen,
set p1959, start the measurement and accept the result.
– You can also determine the moment of inertia using the "Moment of inertia estimator"
function module (see Chapter "Moment of inertia estimator (Page 583)"). As the
moment of inertia is also determined in operation using this function module, we
recommend that the "Moment of inertia estimator" function module is used if the total
moment of inertia changes during operation.