Emerson Powerdrive F300 Getting Started Manual page 93

8.1.3 RFC-S Sensorless mode
Permanent magnet motor without Position feedback
Pr 00.046 {05.007} Rated Current
The motor rated current parameter must be set to the maximum continuous current of the motor. The motor rated
current is used in the following:
• Motor thermal overload protection (see section 8.2
information)
Pr 00.042 {05.011} Number Of Motor Poles
The number of motor poles parameter defines the number of electrical revolutions in one whole mechanical
revolution of the motor. This parameter must be set correctly for the control algorithms to operate correctly. When
Pr 00.042 is set to "Automatic" the number of poles is 6.
Pr 00.040 {05.012} Autotune
There are two autotune tests available in RFC-S sensorless mode, a stationary autotune and an inertia
measurement test.
• Stationary Autotune
The stationary autotune can be used to measure all the necessary parameters for basic control. The tests
measures Stator Resistance (05.017), Ld (05.024), No Load Lq (05.068), Maximum Deadtime Compensation
(05.059) and Current At Maximum Deadtime Compensation (05.060). If Enable Stator Compensation (05.049) = 1
then Stator Base Temperature (05.048) is made equal to Stator Temperature (05.046). The Stator Resistance
(05.017) and Ld (05.024) are then used to set up Current controller Kp Gain (04.013) and Current Controller Ki
Gain (04.014). To perform a Stationary autotune, set Pr 00.040 to 1, and provide the drive with both an enable
signal (on terminal 29) and a run signal (on terminal 24).
• Rotating Autotune
In sensorless mode, if Rotating autotune is selected (Pr 00.040 = 2), then a stationary autotune is performed.
• Inertia measurement test
NOTE: It is not possible to perform this test if, after autotune, the ratio No load Lq (05.072) / Ld (05.024) < 1.1 and
Pr 05.064 has been set to Non-salient.
The inertia measurement test can measure the total inertia of the load and the motor. This is used to set the
speed loop gains (see Speed loop gains) and to provide torque feed-forwards when required during acceleration.
The test may give inaccurate results, if the motor rated speed is not set to the correct value for the motor, or if
standard ramp mode is active. During the inertia measurement test a series of progressively larger torque levels
are applied to the motor (20 %, 40 % ... 100 % of rated torque) to accelerate the motor up to 3/4 x Rated Speed
(05.008) to determine the inertia from the acceleration/deceleration time. The test attempts to reach the required
speed within 5 s, but if this fails the next torque level is used. When 100 % torque is used the test allows 60 s for
the required speed to be reached, but if this is unsucessful an Autotune trip is initiated. To reduce the time taken
for the test it is possible to define the level of torque to be used for the test by setting Mechanical Load Test Level
(05.021) to a non-zero value. When the test level is defined the test is only carried out at the defined test level and
60 s is allowed for the motor to reach the required speed. It should be noted that if the maximum speed allows for
flux weakening then it may not be possible to achieve the required torque level to accelerate the motor quickly
enough. If this is the case, the maximum speed reference should be reduced. To perform an Inertia measurement
autotune, set Pr 00.040 to 4, and provide the drive with both an enable signal (on terminal 29) and a run signal
(on terminal 24).
Following the completion of an autotune test the drive will go into the inhibit state. The drive must be placed into a
controlled disable condition
before the drive can be made to run at the required reference. The drive can be put in to a controlled disable
condition by removing the Safe
Torque Off signal from terminal 29, setting the drive Enable Parameter (06.015) to OFF (0) or disabling the drive
via the control word
(Pr 06.042 & Pr 06.043).
Pr 03.079 Sensorless Mode Filter
When RFC-S sensorless mode is active the measured speed can include some ripple, which increases as the
drive passes into field weakening. A filter is applied to the estimated speed and Sensorless Mode Filter (03.079)
defines the time constant. The default time constant is 4 ms, but this can be extended to improve the filtering. This
is particularly useful when using standard ramp or spinning start with a low friction high inertia load, and can
prevent over voltage trips when the drive has no braking resistor.
Powerdrive F300 Getting Started Guide
Issue Number: 5
Defines the maximum motor continuous current
Motor thermal protection
Defines the number of motor poles
on page 96, for more
93