Technical information

8 – THEORY OF OPERATION
Current Follower
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8.7 Current Follower
When the Starter Type parameter is set to Current Follower, the MX is configured to operate as a Closed Loop current follower.
Current Follower mode can be used to control the current applied to motors, resistive heaters, etc. The Current Follower mode uses
the analog input to receive the desired current command and controls the SCRs to output the commanded current. The MX’s
reference command can be generated from any 0-10V, 0-20mA, 4-20mA source such as a potentiometer, another MX, or an external
controller such as a PLC. When a start command is given, the RUN programmed relay output energizes and the SCRs are gated.
MX Current Follower Mode
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100
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Analog Input (%)
Current Output (% FLA)
Current
Output
A reference input value of 0% results in no output. A reference input value of 100% results in a current output equal to the FLA
setting. The actual voltage or current input that results in a given output can be adjusted through the use of the Analog Input Offset
and Analog Input Span parameters.
Note: The power stack must be rated for continuous non-bypassed duty in order to operate in Current Follower mode continuously.
Note: When operating in Current Follower mode, the acceleration ramp, kick, and deceleration settings have no effect on operation.
Note: When in Current Follower mode the following motor / starter protective functions are available:
- Current Imbalance - Phase Loss
- Over Current - Phase Rotation
- Under Current - Current while Stopped.
- Over Voltage - Motor OL
- Under Voltage - Residual Ground Fault
- Over Frequency - Instantaneous Over Current (IOC)
- Under Frequency