Emerson unidrive sp, User Manual

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138
Unidrive SP Advanced User Guide
www.controltechniques.com Issue Number: 10
Open-loop
When the drive is enabled with this parameter at zero, the output frequency starts at zero and ramps to the required reference. When the drive is
enabled with this parameter at a non-zero value, the drive performs a start-up test to determine the motor speed and then sets the initial output
frequency to the synchronous frequency of the motor. The test is not carried out, and the motor frequency starts at zero, if the run command is given
when the drive is in the stop state, or when the drive is first enabled after power-up with Ur_I voltage mode, or when the run command is given with
Ur_S voltage mode. With default parameters the length of the test is approximately 200ms, however, if the motor has a short rotor time constant
(usually small motors) the time may be shorter. The drive will set the test time automatically if the motor parameters, including the rated load rpm, are
set up correctly for the motor.
For the test to operate correctly it is important that the stator resistance (Pr
5.17 , Pr 21.12 ) is set up correctly. This applies even if fixed boost (Fd) or
square law (SrE) voltage mode is being used. The test uses the rated magnetizing current of the motor during the test, therefore the rated current
(Pr
5.07 , Pr 21.07 and Pr 5.10 , Pr 21.10 ) and power factor should be set to values close to those of the motor, although these parameters are not as
critical as the stator resistance. For larger motors it may be necessary to increase Pr 5.40 (spin start boost) from its default value of 1.0 for the drive
to successfully detect the motor speed.
It should be noted that a stationary lightly loaded motor with low inertia may move slightly during the test. The direction of the movement is undefined.
Restrictions may be placed on the direction of this movement and on the frequencies detected by the drive as follows:
Closed-loop vector and Servo
When the drive is enabled with this bit at zero, the post ramp reference (Pr 2.01 ) starts at zero and ramps to the required reference. When the drive is
enabled with this parameter at one, the post ramp reference is set to the motor speed. When closed-loop vector mode is used without position
feedback (RFC mode), and catch a spinning motor is not required, this parameter should be set to zero as this avoids unwanted movement of the
motor shaft when zero speed is required. When closed-loop vector mode without position feedback (RFC mode) is used with larger motors it may be
necessary to increase Pr
5.40 (spin start boost) from its default value of 1.0 for the drive to successfully detect the motor speed.
This parameter permanently enables the Stop key on the drive such that the drive will always stop when the Stop key is pressed. If keypad mode is
selected this has no effect because the Stop key is automatically enabled.
The sequencer logic has been designed so that pressing the Stop key, whether the Stop key is enabled or not, does not make the drive change from
a stopped to a running condition. As the Stop key is also used to reset trips this means that if the Stop key is pressed when the drive is tripped, the trip
will be reset, but the drive does not start. (This does not apply to the UU trip which cannot be reset by the user, but is automatically reset when the d.c.
link voltage is high enough). Preventing the drive from starting when the stop key is pressed is implemented as follows.
Sequencer latching not enabled (Pr 6.40=0)
If the Stop key is pressed when the Stop key is enabled (Pr 6.12 =1) or when the drive is tripped the sequencer run is removed, and so the drive stops
or remains stopped respectively. The sequencer run can only then be reapplied after at least one of the following conditions occurs.
1. Run forward, Run reverse and Run sequencing bits all zero
2. OR the drive is disabled via Pr
6.15 or Pr 6.29
3. OR Run forward and Run reverse are both active and have been for 60ms.
4. The drive is in the UU state.
The drive can then be restarted by activating the necessary bits to give a normal start.
6.09 Catch a spinning motor
Drive modes Open-loop, Closed-loop vector, Servo
Coding
Bit SP FI DE TE VM DP ND RA NC NV PT US RW BU PS
1 1 1
Range
Open-loop
Closed-loop vector, Servo 3
1
Default
Open-loop
Closed-loop vector, Servo 0
1
Update rate Background read
Pr 6.09 Function
0 Disabled
1 Detect all frequencies
2 Detect positive frequencies only
3 Detect negative frequencies only
6.12 Enable stop key
Drive modes Open-loop, Closed-loop vector, Servo
Coding
Bit SP FI DE TE VM DP ND RA NC NV PT US RW BU PS
1 1 1
Default Open-loop, Closed-loop vector, Servo 0
Update rate Background read