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HVAC Drive H300 157
Issue Number: 3
8.1.3 RFC-S Sensorless mode
Permanent magnet motor without Position feedback
Pr 00.020 {05.007} Rated Current Defines the maximum motor continuous 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 Motor thermal protection on page 160, for more information)
Pr 00.017 {05.011} Number Of Motor Poles Defines the 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 00.017 is set to "Automatic" the number of poles is 6.
Pr 00.024 {05.012} Autotune
There are two autotune tests available in RFC-S sensorless mode, a stationary autotune and an inertia measurement test.
• Autotune test 1: 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) and No Load Lq (05.068). 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 00.024 to 1, and provide the drive with both an enable signal (on
terminal 29) and a run signal (on terminal 24).
• Autotune test 2: Rotating Autotune
In sensorless mode, if Rotating autotune is selected (Pr 00.024 = 2), then a stationary autotune is performed.
• Autotune test 3: Locked rotor test for load dependant parameters
This test is not implemented at the time of writing.
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. This is
particularly useful when using standard ramp or spinning start with a low friction high inertia load, and can prevent over voltage trips.
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