Yaskawa AC Drive Z1000 AC Drive HVAC Fan - Manual (Page 32)

Run command
Output
frequency
Output current
OFF ON
b3-02
Decel time set
set to b3-03 Waits for twice
as long as L2-04
Selected
frequency
reference
Minimum Baseblock Time (L2-03)
Max. output frequency
or the specified
frequency reference
Figure 1.11 Current Detection Speed Search at Start or Speed Search Command by Digital Input
Notes on Using Current Detection Type Speed Search
• Shorten the Speed Search deceleration time set to b3-03 if an oL1 fault occurs while performing Current Detection Speed
Search.
• Current Detection Speed Search is not available when using OLV Control for PM motors.
• Increase the minimum baseblock time set to L2-03 if an overcurrent or overvoltage fault occurs when performing Speed
Search after power is restored following a momentary power loss.
n Speed Estimation Type Speed Search (b3-24 = 1)
This method can be used for a single induction motor connected to a drive. Do not use this method if the motor is one or more
frame size smaller than the drive, at motor speeds above 200 Hz, or when using a single drive to operate more than one motor.
Speed Estimation is executed in the two steps described below:
Step 1: Back EMF Voltage Estimation
This method is used by Speed Search after baseblock (e.g., a power loss where the drive CPU continued to run and the Run
command was kept active). Here, the drive estimates the motor speed by analyzing the back EMF voltage and outputs the
estimated frequency and increases the voltage using the time constant set in parameter L2-04. After that, the motor is accelerated
or decelerated to the frequency reference starting from the detected speed. If there is not enough residual voltage in the motor
windings to perform the calculations described above, the drive will automatically proceed to step 2.
AC power
supply
Output
frequency
Output
current
OFF ON
Starts at the speed
that was detected
Selected
frequency
reference
Min. Baseblock Time
(L2-03)
Several miliseconds
b3 -05 <1>
Figure 1.12 Speed Search after Baseblock
<1> After 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 insufficient residual voltage in the motor after extended power losses, when Speed
Search is applied with the Run command (b3-01 = 1), or when an External search command is used.
1.2 b: Application
32 YASKAWA ELECTRIC SIEP YAIZ1U 03A YASKAWA AC Drive – Z1000 Programming Manual