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Diagnostics Optimization CT MODBUS RTU Technical Data
230 E300 Design Guide
Issue Number: 1
The position feedback device can be aligned statically by connecting the motor to a d.c. power supply as already shown. The motor will move to one
of a number of positions defined by the number of motor poles (i.e. 3 positions for a six pole motor, etc.). The position feedback device should be
adjusted so that the position displayed by the drive is (n x 65536) / (Number of poles / 2), where n = 0, 1, etc.
RFC Feedback Mode (C14), which can be changed even when the motor is running, selects the feedback method used to provide position feedback
to control the motor. When sensorless mode is used, a filter with a 4 ms time constant is automatically included in the speed feedback as this is
required for this system to operate correctly. The possible speed controller bandwidth will be reduced by a factor of approximately 10 compared with
the bandwidth possible with a position feedback device. The maximum and minimum for the speed references are limited by the
VM_POSITIVE_REF_CLAMP variable minimum/maximum which prevents the speed from exceeding the level where the position feedback cannot
be interpreted correctly. This limit is disabled if RFC Feedback Mode (C14) is 2 or 3, so that it is possible to change between operation with or without
position feedback if the speed range needs to be extended beyond the limit of the position feedback device. Care should be taken not to exceed a
speed that would damage the position feedback device.
0: Position feedback
RFC mode is active using position feedback.
1: Sensorless
RFC mode using a sensorless algorithm to provide position feedback, is used to control the motor.
2: Position feedback with no maximum speed limit
RFC mode with position feedback. The maximum reference limit is disabled.
3: Sensorless with no maximum speed limit
RFC mode using a sensorless algorithm to provide position feedback, is used to control the motor. The maximum reference limit is disabled.
It should be noted that when sensorless mode is active the maximum torque that can be produced at low speeds (i.e. < 2 % or rated speed) is
reduced.
If sensorless mode is being used and is active and the motor speed is below Motor Rated Speed (B07) / 10 then a special low speed algorithm must
be used to control the motor. Sensorless Low Speed Mode (C15) is used to select the algorithm to be used.
0: Injection
A high frequency signal is injected into the motor to detect the motor flux axis. This can be used in a similar way to operation with position feedback
except that for the drive to remain stable the speed controller bandwidth may need to be limited to 10 Hz or less and the current limit may need to be
limited (see Sensorless Mode Low Speed Current (C16)).
C14 RFC Feedback Mode
Mode RFC-A, RFC-S
Minimum 0 Maximum 3
Default 0 Units
Type 8 Bit User Save Update Rate 4ms read
Display Format Standard Decimal Places 0
Coding RW, Txt
Value Text
0 Feedback
1 Sensorless
2 Feedback NoMax
3 Sensorless NoMax
C15 Sensorless Low Speed Mode
Mode RFC-S
Minimum 0 Maximum 1
Default 0 Units
Type 8 Bit User Save Update Rate Background read
Display Format Standard Decimal Places 0
Coding RW, Txt
Value Text
0 Injection
1 Non-salient
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