User Manual

Table Of Contents
Closed Loop Speed Mode with Constant Slip Control
Advanced Digital Motor Controller User Manual 137
Watt
V
Amps
RPM
Nm
50Hz
Encoder 64 Pulses
3500
48Bat
100
1450
23
V fase 3 x 27
FIGURE 9-5. ACIM label
For this motor, the VPH can be determined by dividing the 48 V phase to phase motor
voltage amplitude by the 50Hz frequency. In this case 0.96 Volts per Hertz. It is worth
mentioning that the rated voltage in the calculated VPH is related to the amplitude of the
phase to phase voltage (not RMS value). Therefore, if the motor manufacturer provides
the nominal stator voltage in RMS, it should be transformed to peak voltage value.
You can validate that the rated VPH is applied if the motor at no load reaches the rated
speed when applying maximum motor command ( Power =1000).
Note that this value is for the optimal torque as rated on the label. If the load is a lot light-
er, the VpH will be too high and result in excessive current consumption. If the load is a
lot heavier, the VpH will be too low and the motor will not be able to drive it. The VpH will
therefore need to be different from this computed based on actual load conditions. Always
first monitor the motor consumption at no load. Adjust the VpH to a lower value if the no
load current appears too high.
Maintaining Slip within Safe Range
Open Loop, or Scalar, the mode does not require encoders for its operation. If the load is
known to always be within the motor’s max torque, the motor can be trusted to always
be able to drive it. In this case, an encoder does not need to be connected. If an encoder
is connected - to measure and report speed, for example - then it must be configured as
“No Action” in the PC Utility.
For added safety, however, an encoder can be installed and enabled to measure the ro-
tor’s speed, and therefore the slip, in real-time. When the encoder is enabled and config-
ured as “Feedback”, the controller will lower the voltage and frequency if the slip exceeds
twice the value stored in the Optimal Slip configuration.
Prior to enabling the encoder as Feedback, verify that the encoder count direction has the
same polarity as the motor command.
Closed Loop Speed Mode with Constant Slip Control
In this mode, the controller will automatically adjust the voltage and frequency in order to
reach and maintain the desired speed, even as the load is changing, while operating with-
in the optimal slip range.