YASKAWA A1000 Series Technical Manual page 148

5.2 b: Application
Figure 5.19
AC power
frequency
<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.
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 5.20
Run command
Output
frequency
Output
current
Min. Baseblock Time (L2-03)
<1> The wait time for Speed Search (b3-05) determines the lower limit.
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 the 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 Search 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.
148
supply
ON OFF
Output
Output
current
Min. Baseblock Time
(L2-03)
Figure 5.19 Speed Search after Baseblock
Decelerates at the Speed
Search decel time set to b3-03
ON
OFF
Starts at the speed
speed that was detected
1.0 s
<1>
Figure 5.20 Speed Search at Start
Starts at the speed
that was detected
Several miliseconds
b3 -05 <1>
Waits twice as long as L2-04
YASKAWA ELECTRIC SIEP C710616 27C YASKAWA AC Drive A1000 Technical Manual
Selected
frequency
reference
common_TMonly
Frequency reference
set to the drive
common_TMonly
b3-02