Sensorless Vector Control - Hitachi SJ700-2 Instruction Manual

Sj700-2 series
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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
starting
for 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 "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%
Chapter 4 Explanation of Functions
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 - 90
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
Adjustment item
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

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