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Unidrive SPM User Guide
17
Issue Number: 3 www.controltechniques.com
3.2 Operating modes
The Unidrive SPM is designed to operate in any of the following modes:
1. Open loop mode
Open loop vector
Fixed V/F mode (V/Hz)
Quadratic V/F mode (V/Hz)
2. RFC mode
3. Closed loop vector
4. Servo
5. Regen
3.2.1 Open loop mode
For use with induction motors.
The drive applies power to the motor at frequencies varied by the user.
The motor speed is a result of the output frequency of the drive and slip
due to the mechanical load. The drive can improve the speed control of
the motor by applying slip compensation. The performance at low speed
depends on whether V/F mode or open loop vector mode is selected.
Open loop vector mode
The voltage applied to the motor is directly proportional to the frequency
except at low speed where the drive uses motor parameters to apply the
correct voltage to keep the flux constant under varying load conditions.
Typically 100% torque is available down to 1Hz for a 50Hz motor.
For further details refer to section 10.1.1
Open loop motor control
on
page 136.
Fixed V/F mode
The voltage applied to the motor is directly proportional to the frequency
except at low speed where a voltage boost is provided which is set by
the user. This mode can be used for multi-motor applications.
Typically 100% torque is available down to 4Hz for a 50Hz motor.
Quadratic V/F mode
The voltage applied to the motor is directly proportional to the square of
the frequency except at low speed where a voltage boost is provided
which is set by the user. This mode can be used for running fan or pump
applications with quadratic load characteristics or for multi-motor
applications. This mode is not suitable for applications requiring a high
starting torque.
3.2.2 RFC mode
Rotor flux control provides closed loop control without the need for
position feedback by using current, voltages and key motor parameters
to estimate the motor speed. It can eliminate instability traditionally
associated with open loop control such as operating large motors with
light loads at low frequencies.
For further details refer to section 10.1.2
RFC mode
on page 138.
3.2.3 Closed loop vector mode
For use with induction motors with a feedback device installed.
The drive directly controls the speed of the motor using the feedback
device to ensure the rotor speed is exactly as demanded. Motor flux is
accurately controlled at all times to provide full torque all the way down
to zero speed.
For further details refer to section 10.1.3
Closed loop vector motor
control
on page 141.
3.2.4 Servo
For use with permanent magnet brushless motors with a feedback
device installed.
The drive directly controls the speed of the motor using the feedback
device to ensure the rotor speed is exactly as demanded. Flux control is
not required because the motor is self excited by the permanent
magnets which form part of the rotor.
Absolute position information is required from the feedback device to
ensure the output voltage is accurately matched to the back EMF of the
motor. Full torque is available all the way down to zero speed.
For further details refer to section 10.1.4
Servo motor control
on
page 144.
3.2.5 Regen
For use as a regenerative front end for four quadrant operation.
Regen operation allows bi-directional power flow to and from the AC
supply. This provides far greater efficiency levels in applications which
would otherwise dissipate large amounts of energy in the form of heat in
a braking resistor.
The harmonic content of the input current is negligible due to the
sinusoidal nature of the waveform when compared to a conventional
bridge rectifier or SCR/thyristor front end.
See the
Unidrive SP Regen Installation Guide
for more information
about operation in this mode.
3.3 Compatible encoders
Table 3-14 Encoders compatible with Unidrive SPM
* This feedback device provides very low resolution feedback and should
not be used for applications requiring a high level of performance
Encoder type
Pr 3.38 setting
Quadrature incremental encoders with or without
marker pulse
Ab (0)
Quadrature incremental encoders with UVW
commutation signals for absolute position for
permanent magnet motors with or without marker
pulse
Ab.SErvo (3)
Forward / reverse incremental encoders with or
without marker pulse
Fr (2)
Forward / reverse incremental encoders with
UVW commutation signals for absolute position
for permanent magnet motors with or without
marker pulse
Fr.SErvo (5)
Frequency and direction incremental encoders
with or without marker pulse
Fd (1)
Frequency and direction incremental encoders
with UVW commutation signals for absolute
position for permanent magnet motors with or
without marker pulse
Fd.SErvo (4)
Sincos incremental encoders
SC (6)
Heidenhain sincos encoders with Endat comms
for absolute position
SC.EndAt (9)
Stegmann sincos encoders with Hiperface comms
for absolute position
SC.HiPEr (7)
Sincos encoders with SSI comms for absolute
position
SC.SSI (11)
SSI encoders (Gray code or binary)
SSI (10)
Endat comms only encoders
EndAt (8)
UVW commutation only encoders*
Ab.SErvo (3)
