5.2 b: Application
162 YASKAWA ELECTRIC SIEP C710616 27G YASKAWA AC Drive A1000 Technical Manual
Figure 5.22
<1> Once AC power is restored, the drive will wait for at least the time set to b3-05. If the power interruption is longer than the minimum
baseblock time set to L2-03, the drive will wait until the time set to b3-05 has passed after power is restored before starting Speed
Search.
Figure 5.22 Speed Search after Baseblock
Step 2: Current Injection
Current Injection is performed when there is not enough residual voltage remaining in the motor. This might occur after
after longer power losses, when Speed Search is applied with the Run command (b3-01 = 1), or if an External search
command is used. It injects the DC current set in b3-06 to the motor and detects the speed by measuring the current
feedback. The drive outputs the detected frequency and increases the voltage using the time constant set in parameter
L2-04 while looking at the motor current. If the current is higher than the level in b3-02, then the output frequency is
reduced. When the current falls below b3-02, the motor speed is assumed to be found and the drive starts to accelerate or
decelerate to the frequency reference.
Figure 5.23
<1> The wait time for Speed Search (b3-05) determines the lower limit.
Figure 5.23 Speed Search at Start
Notes on Using Speed Estimation Speed Search
• Rotational Auto-Tuning for V/f Control (T1-01 = 3) needs to be first performed if you plan to use Speed Estimation in
V/f Control. Perform Stationary Auto-Tuning for Line-to-Line Resistance (T1-01 = 2) again if the there is a change in
the cable length between the drive and motor.
• Use Current Detection to search for speeds
beyond 200 Hz, if the application is running multiple motors from the same
drive, or if the motor is considerably smaller than the capacity of the drive.
• Speed Estimation may have trouble finding th
e actual speed if the motor cable is very long. Current Detection should
be used in such situations.
• Use Current Detection instead of Speed Estimation when operating motors smaller
than 1.5 kW. Speed Estimation can
end up stopping smaller motors, as it might not be able to detect the speed or rotation direction of such small motors.
• Short Circuit Braking is recommended instead of Speed Sea
rch when using OLV/PM and AOLV/PM along with a
fairly long motor cable.
• Use Short Circuit Braking instead of Speed Search if attempting to find the speed of a motor
coasting faster than 200
Hz in OLV/PM and AOLV/PM.
AC power
supply
Output
frequency
Output
current
OFFON
Starts at the speed
that was detected
Selected
frequency
reference
Min. Baseblock Time
(L2-03)
Several miliseconds
b3 -05
<1>
Run command
Output
frequency
Output
current
OFF
ON
b3-02 (Speed search operation current)
Starts at the speed
speed that was detected
Waits twice as long as L2-04
Frequency reference
set to the drive
Decelerates at the Speed
Search decel time set to b3-03
1.0 s
Min. Baseblock Time (L2-03)
<1>
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