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Chapter 4 Explanation of Functions
4 - 89
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
status
Symptom Adjustment method Adjustment item
Momentary speed
variation is negative.
Increase the motor constant R2 step by step from the
set value up to 1.2 times as high as the set value.
H021/H221/H031
Powering
Momentary speed
variation is positive.
Reduce the motor constant R2 step by step from the set
value down to 0.8 times as high as the set value.
H021/H221/H031
Increase the motor constant R1 step by step from the
set value up to 1.2 times as high as the set value.
H020/H220/H030
Regenerating
Torque is insufficient at
low frequencies
(several Hz)
Increase the motor constant Io step by step from the set
value up to 1.2 times as high as the set value.
H023/H223/H033
Starting
The motor generates an
impact when it starts.
Reduce the motor constant J from the set value. H024/H224/H034
Reduce the speed response setting. H005/H205
Decelerating
The motor runs
unsteadily.
Reduce the motor constant J from the set value. H024/H224/H034
Torque-limited
operation
Torque is insufficient
during torque-limited
operation at a low
frequency.
Reduce the overload restriction level to lower than the
torque limiter level.
b021, b041 to b044
Low-frequency
operation
Motor rotation is
inconsistent.
Increase the motor constant J from the set value. H024/H224/H034
starting
Motor runs backwards
for short moment.
Set 01 (enable) on reverse run protection function
(b046)
b046
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 "α" calculated by the expression below does not exceed
200%. Otherwise, the motor may be burnt out.
α = "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 "α" should
be 200%:
Torque limit (b041 to b044) = α x (motor capacity)/(inverter capacity) = 200% x (0.4
kW)/(0.75 kW) = 106%
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
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