Sensorless Vector, 0 Hz Domain Control - Hitachi SJ700-2 Instruction Manual

4.2.97 Sensorless vector, 0 Hz domain control

The 0Hz domain sensorless vector (SLV) control function
incorporates Hitachi's own torque control system and
enables high-torque operation in the 0Hz range (0 to 3 Hz).
This control function is best suited for driving a lifting
machine, e.g., crane or hoist, that requires sufficient torque
when starting at a low frequency.
To use this function, specify "04" for the V/F characteristic
curve selection (A044/A244).
Before using this function, be sure to optimize constant
settings for the motor with reference to Section 4.2.91,
"Motor constant selection."
The parameters related to the 0Hz-range sensorless vector
control are as follows:
1) The Zero LV lmit for 1st/2nd motors (H060/H260) is the
parameter that specifies the output current for the constant-
current control in the 0 Hz range (about 3.0 Hz or less). The
parameter value is expressed as a ratio of the output current
to the inverter's rated current.
2) The Zero LV starting boost current (H061/H261) is the parameter to specify the current for boosting at
motor start-up with a frequency in the 0 Hz range. The parameter value is expressed as a ratio of the
boost current to the inverter's rated current. The value of the boost current is added to the current value
specified by "H060/H260" only at starting.
Item
Zero LV lmit
Zero LV starting boost current
When using this function, observe the following precautions:
1) Be sure to use an inverter of which the capacity is one class higher than the motor to be driven.
2) 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.
3) If you cannot obtain desired characteristics from the motor driven under the 0Hz-range 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.
Immediately Overcurrent or
after overvoltage protection
deceleration function operates.
Low-frequency Motor rotation is
operation inconsistent.
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: 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 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%
Function code Range of data
H060/H260 0.0 to 100.0 (%)
H061/H261 0. to 50. (%)
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 I0 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 motor constant I0 step by step from the set
value down to 0.8 times as high as the set value.
Specify "00" (always on) or "01" (always off) for the
AVR function select (A081).
Increase the motor constant J from the set value.
4 - 91
Chapter 4 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 limit (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 m
H020/H2 20: 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 motor
H051/H251: PI integral gain, 1st/2nd motors
H052/H252: P proportional gain setting, 1st/2
motors
H060/H260: Zero LV lmit, 1st/2nd motors
H061/H261: Zero LV starting boost current
1st/2nd motors
Current limiter for the low-speed range
Quantity of boost current at starting
oto rs
s
nd
,
Description
Adjustment item
H021/H221/H031
H021/H221/H031
H020/H220/H030
H023/H223/H033
H024/H224/H034
H005/H205
H024/H224/H034
H023/H223/H033
A081
H024/H224/H034