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Chapter 4
4.2.96 Sensorless vector control
The sensorless vector control function estimates and controls the
motor speed and output torque on the basis of the inverter output
voltage and output current and the motor constants set on the
inverter. This function enables the inverter to accurately operate the
motor with a high starting torque, even at a low frequency (0.3 Hz
or more).
To use this function, specify "03" for the V/F characteristic curve
selection (A044/A244).
Before using this function, be sure to make optimum constant
settings for the motor with reference to Section 4.2.91, "Motor
constant selection."
When using this function, observe the following precautions:
1) If you use the inverter to drive a motor of which the capacity is
two classes lower than the maximum applicable capacity of the
inverter, you may not be able to obtain adequate motor
characteristics.
2) If you cannot obtain the desired characteristics from the motor driven under the sensorless vector control,
readjust the motor constants according to the symptom, as described in the table below.
Operation
Symptom
status
Momentary speed
variation is negative.
Powering
Momentary speed
variation is positive.
Torque is insufficient at
Regenerating
low frequencies (several
Hz)
The motor generates an
Starting
impact when it starts.
The motor runs
Decelerating
unsteadily.
Torque is insufficient
Torque-limited
during torque-limited
operation
operation at a low
frequency.
Low-frequency
Motor rotation is
operation
inconsistent.
Motor runs backwards for
starting
short moment.
Note 1: Always set the carrier frequency (b083) to 2.1 kHz or more. If the carrier frequency is less than 2.1 kHz, the
inverter cannot operate the motor normally.
Note 2: When driving a motor of which the capacity is one class lower than the inverter, adjust the torque limit (b041
to b044) so that the value "" calculated by the expression below does not exceed 200%. Otherwise, the
motor may be burnt out.
= "torque limit" x (inverter capacity)/(motor capacity)
(Example)
When the inverter capacity is 0.75 kW and the motor capacity is 0.4 kW, the torque limit value is
calculated as follows, based on the assumption that the value "" should be 200%:
Torque limit (b041 to b044) = x (motor capacity)/(inverter capacity) = 200% x (0.4 kW)/(0.75
kW) = 106%
Adjustment method
Increase the motor constant R2 step by step from the set
value up to 1.2 times as high as the set value.
Reduce the motor constant R2 step by step from the set
value down to 0.8 times as high as the set value.
Increase the motor constant R1 step by step from the set
value up to 1.2 times as high as the set value.
Increase the motor constant Io step by step from the set
value up to 1.2 times as high as the set value.
Reduce the motor constant J from the set value.
Reduce the speed response setting.
Reduce the motor constant J from the set value.
Reduce the overload restriction level to lower than the
torque limiter level.
Increase the motor constant J from the set value.
Set 01 (enable) on reverse run protection function (b046)
4-89
Explanation of Functions
Related code
A001: Frequency source setting
A044/A244: V/F characteristic curve selection, 1st/2nd
motors
F001: Output frequency setting
b040: Torque limit selection
b041 to b044: Torque limits (1) to (4)
H002/H202: Motor data selection, 1st/2nd motors
H003/H203: Motor capacity, 1st/2nd motors
H004/H204: Motor poles setting, 1st/2nd motors
H005/H205: Motor speed constant, 1st/2nd motors
H020/H220: Motor constant R1, 1st/2nd motors
H021/H221: Motor constant R2, 1st/2nd motors
H022/H222: Motor constant L, 1st/2nd motors
H023/H223: Motor constant Io, 1st/2nd motors
H024/H224: Motor constant J, 1st/2nd motors
H050/H250: PI proportional gain, 1st/2nd motors
H051/H251: PI integral gain, 1st/2nd motors
H052/H252: P proportional gain setting, 1st/2nd
motors
H021/H221/H031
H021/H221/H031
H020/H220/H030
H023/H223/H033
H024/H224/H034
H005/H205
H024/H224/H034
b021, b041 to b044
H024/H224/H034
b046
Adjustment item
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