NORD Drivesystems BU0510 - Manual (Page 64)

POSICON position control for NORD frequency inverters, SK 530E and above
64 Subject to technical alterations BU 0510 GB-3911
6.4 Setting the speed and position controls
The speed and position controls are set as would be the case if there was no synchronous operation.
Therefore, if possible, the speed control should first be set in parameter P300 "Servo Mode", then the position
control in parameter P600 "Position Control" and then the synchronisation control should be commissioned.
The dynamic results are improved, the more sharply the controls can be set. From experience however, the
position control functions better if the I component in the speed control is not too large. The speed control
should therefore be set for a slight overshoot. This results in a P component which is as high as possible (until
noises occur at low speeds), and a rather moderate I component. The setting of the torque limits and the
selected ramps must be made so that the drive can always follow the ramp.
6.5 Taking a speed ratio between master and slave into account
A speed ratio between the master and the slave can be taken into account via the parameters P607 "Speed
Ratio" and P608 "Reduction Ratio".
For SK 53xE devices the entries are made in the arrays of the encoder type which is not used.
For SK 54xE devices an appropriate Array [-05] is available for the entries.
N
Slave
= P607 [ - xx] / P608 [ - xx] * N
Master
P105
Slave
= P607 [ - xx] / P608 [ - xx] * P105
Master
* 1,05 ... 1,5
P410
Slave
= 0
P411
Slave
= P105
Master
There is also the possibility of changing the speed ratio between the master and the slave via an analog input.
The ratio can be continuously varied between -200% and a maximum of 200% of the master speed. The
analog input can be scaled via the parameters P402/P404 and P403/P408 (see Manual BU 0500) according to
requirements. For negative values there is a change of direction of rotation. The function of the analog inputs
(P400, P405) should be set to Function 47 = Speed ratio factor. It is possible to adjust the speed ratio "online",
however, it should be noted that the "Position slip error" in parameter P630 "Position Slip Error" can take on
considerably larger values than for normal synchronous operation during the adjustment, as acceleration or
braking to the new speed must be performed.
6.6 Monitoring functions
6.6.1 Achievable precision / Position monitoring
The achievable precision, i.e. the deviation of the master and slave drives depends on several factors. Here, in
addition to the settings of the speed control and the position control, the path, i.e. the drive or the mechanics of
the system, play a decisive role. The minimum value of the achievable precision is however determined by the
type of transmission. A deviation of at least 0.1 rotations should be expected. In practice, a value of more than
0.25 motor rotations should be planned for. The deviation between the master and the slave can be monitored
by the relay function "Position Reached" with the slave. The relay switches off if the set value in P625 "Output
Hysteresis" is exceeded or the difference between the specified and the actual speed 2Hz + the set value in
P104 "Minimum Frequency" is exceeded. The minimum frequency for the slave can be calculated with the
following formula:
P104 = 0.25 ... 1,0 * (P625 [Rotation] * 4,0Hz * P611 [%]) – 2Hz
For a permissible deviation of one rotation and a position control P of 5% this results in a speed component for
the position control of 20Hz. If P104 "Minimum Frequency" is set to a considerably lower value, the relay
message is determined by the exceeding of the speed by the slave and not by the maximum deviation in
position. This especially applies, the shorter the ramp times are set for the slave.