Siemens SIMOVERT MASTERDRIVES Manual page 222

Functions
7.3.4 Position test function
1. Switching on
2. Setpoint
3. Encoder
adjustment
7-56
On synchronous motors, the torque control must be able to detect the
position of the rotor in the motor so that the current is always injected at
the correct position. That position is supplied by the encoder, which is
installed in the motor (resolver, multiturn encoder, encoder). The
encoder is mounted on the rotor wit the correct alignment in the factory.
However, if the encoder is replaced as the result of a fault or if a non-
Siemens synchronous motor is operated on the MASTERDRIVES
converter, the alignment of the encoder and the direction of rotation
must be checked and corrected, if necessary.
The position test consists of injecting a current with a fixed angular
position into the stator of the synchronous motor. The rotor must be
free to move so that it can align itself toward the injected current with its
permanent magnet (if necessary, release the holding brake and
decouple from the mechanical system).
The converter switches to status "Operation with position test" when the
ON command is output and while parameter P115 = 8 or value 1 is
pending on binector input "Source position test" (P549).
The user must set a current setpoint so that the motor aligns itself (e.g.
100 % at P260 "source M(set)" or 1 % speed setpoint, which also
results in 100 % torque setpoint via the speed controller).
The current causes the free moving motor to align itself to the fixed
electrical angle. Depending on the number of poles of the motor, this
will be one of several possible mechanical angular positions within one
revolution of the motor. (For example, for a six-pole motor there are
three mechanical angular positions within one revolution into which the
motor can lock. It is of no consequence for the adjustment into which of
the three positions the motor locks.)
The incorrect orientation of the encoder can be read off in mechanical
degrees in r286 "position test angle" (function diagram 390). A value of
± 1° mechanical for motors with a low number of poles (<= 8 poles) lies
within the range of measuring inaccuracy and need not be altered. (This
degree of inaccuracy can even be induced by turning the motor shaft
slightly by hand during measurement.)
When the encoder is replaced, correction should preferably be made
mechanically, i.e. by disconnecting the encoder, turning it until the
"position test angle" r286 shows the value 0° and then tightening it again
so that the encoder is again installed in the position as set in the factory.
If it is not completely safe to align the encoder mechanically during
operation, the deviation can also be corrected by parameterizing an
offset in P132 "angular offset" to a position test angle r286 of 0°. Making
the correction in the parameters is especially recommended for motors
of non-Siemens suppliers who install their encoders in a standard
position other than that of SIEMENS. During operation with position
test, it is possible to change parameter P132 "angular offset" manually
with the position test, or reduce it automatically with a falling edge at
binector input "source position test" (P549) by the current displayed
value r286 "position test angle".
In both cases, the position test angle r286 must finally show the value
0°.
6SE7087-6QX70 (Version AG)
Compendium Motion Control
05.2006
Siemens AG
SIMOVERT MASTERDRIVES