YASKAWA T1000A Technical Manual page 123

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 5.19
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.
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Residual Voltage Detection Speed Search
This method detects the motor speed and rotation direction my measuring the residual voltage from the rotating motor.
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Activating of Speed Search
Speed Search can be activated as described below. Note that the Speed Search type must be selected in parameter b3-24
independent of the activation method.
1. Automatically activate Speed Search with every Run command. Here, external Speed Search commands are ignored.
2. Activate Speed Search using the digital input terminals.
The following input functions for H1-
Setting Description
61 External Search Command 1
62 External Search Command 2
To activate Speed Search by a digital input, the input must always be set together with the Run command, or the Run
YASKAWA ELECTRIC SIEP C710616 30B YASKAWA AC Drive T1000A Technical Manual
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 5.19 Speed Search at Start
can be used.
Table 5.7 Speed Search Activation by Digital Inputs
b3-24 = 0
Closed: Activate Current Detection Speed Search from the
maximum output frequency (E1-04).
Closed: Activate Current Detection Speed Search from the
frequency reference.
Waits twice as long as L2-04
Frequency reference
set to the drive
b3-02
Activate Speed Estimation Speed Search
5.2 b: Application
5
b3-24 = 1
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