YASKAWA iQpump Micro CIMR-PW Series User Manual page 125

<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 L2-03, the drive will wait for b3-05 after the power has returned before starting Speed Search.
Current Injection
This method is used when there is no detectable back EMF, e.g. 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. If the resulting current is higher than the level in b3-02 the output frequency
is reduced. When the current becomes lower than b3-02 the motor speed is assumed to be found and the drive starts to accelerate
or decelerate to the frequency reference.
command
Output
frequency
Output
current
Min. Baseblock Time (L2-03)
<1> The wait time for Speed Search (b3-05) determines the lower limit.
Note: If the Run command is quickly switched off and then back on again when the drive is set to "Coast to stop" as the stopping method, Speed
Search will operate as shown in
Notes on Using Speed Estimation Type Speed Search
• Auto-Tuning needs to be first performed if you plan to use Speed Estimation. Perform Auto-Tuning again if the there is a
change in the cable length between the drive and motor.
• Use Current Detection to search for speeds beyond 130 Hz or 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 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.
Current Detection Type Speed Search (b3-24 = 0)
n
Current Detection Speed Search can be applied to any motor. Be aware that sudden acceleration may occur when using Current
Detection with relatively light loads.
This method detects the motor speed by reducing the output frequency and measuring the current. The frequency reduction
starts from the maximum output frequency or from the set frequency reference. As long as the output frequency is higher than
the rotor speed, the slip will cause a high current. The closer the output frequency comes to the rotor speed, the lower the
current draw will be. When the output current drops below the level as set in b3-02, the output frequency stops decreasing and
normal operation resumes.
The following time chart illustrates how Current Detection Speed Search operates after a momentary power loss:
YASKAWA TOEP YAIQPM 03B YASKAWA AC Drive - iQpump Micro User Manual
Decelerates at the Speed
Search decel time set to b3-03
ON
OFF
Run
Starts at the detected speed
1.0 s
<1>
Figure 5.14 Speed Search at Start
Figure 5.13.
Waits for L2-04 x 2 time
Frequency reference
set to the drive
b3-02
5.2 b: Application
5
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