Siemens SIMOVERT MASTERDRIVES Manual page 220

Functions
Using the
kT estimator
7-54
The kT estimator needs the most exact possible motor parameter
values in order to attain high torque accuracy. Before use is made of
the kT estimator, motor identification (P115 = 2) must therefore be
performed to define the values for P119, P120 and P121. The motor
should be at room temperature for identification.
The motor temperature is needed by the estimator for tracking the
temperature-dependent variables. If no motor temperature sensor is
wired up, good accuracy is attained only during operation at the
temperature at which motor identification was performed.
The kT estimator is not activated until a definite speed (P091.1) is
reached. The voltage at the converter terminals is always subject to
minor errors, introduced by voltage drops at the semiconductors, etc.
The lower the speed and hence the output voltage, the more the
estimate is disturbed by minor voltage errors. That is why the estimate
is turned off below a definite speed (factory setting: 20 % of rated
speed). When the speed falls below this level, the last-estimated value
is frozen.
The estimator is activated by setting the maximum deviation (P091.2) to
a value greater than 0 %. To turn on the estimator, this value can be set
to 30 %.
The standstill torque constant (P098) is preassigned with the stored
value in the case of a Siemens motor, and with the value
M_rated/i_rated in the case of a non-Siemens motor. The value can
vary as a result of manufacturing tolerances. If the estimator has been
activated and the motor speed is higher than the selected speed, a
corrected standstill torque constant value can be read from visualization
parameter r088. This value can then be entered in P098.
The temperature dependence (P090.2) of the magnet material is set to
12 % at the factory. This means that magnetization declines by 12 %
when the temperature of the rotor rises by 100 K. This is the usual
value for the neodymium-iron-boron magnet material now used. If no
temperature sensor is connected, the temperature adaptation is turned
off.
The temperature adaptation is also effective when the estimated value
is frozen or when the estimator was turned off with P091.2 = 0.
6SE7087-6QX70 (Version AG)
Compendium Motion Control
05.2006
Siemens AG
SIMOVERT MASTERDRIVES