
Parameter b2-13 sets the time for Short-Circuit brake operation at stop. Disabled when set to 0.00 s.
No.
Name
Setting Range
Default
b2-13
Short Circuit Brake Time at Stop
0.00 to 25.50 s
0.50 s
u
b3: Speed Search
The Speed Search function allows the drive to detect the speed of a rotating motor shaft that is driven by external forces (e.g.
fan rotating by windmill effect or motor driven by load inertia). The motor operation can be directly started from the speed
detected without needing to stop the machine before.
Example: When a momentary loss of power occurs, the drive output shuts off. This results in a coasting motor. When power
returns, the drive can find the speed of the coasting motor and restart it directly.
The drive offers two types of Speed Search, Speed Estimation and Current Detection. Both methods are explained below
followed by a description of all relevant parameters.
n
Speed Estimation Type Speed Search (b3-24 = 1)
This method can be used for a single motor connected to a drive. It should not be utilized if the motor is one or more frame
sizes smaller than the drive, at motor speeds above 130 Hz, or when using a single drive to operate more than one motor.
The Speed Estimation type distinguishes two kinds of operation, Back EMF voltage estimation and DC current injection.
Back EMF Voltage Estimation
This method is used by Speed Search after short Baseblock (e.g. a power loss where the drives CPU kept running and the Run
command was kept active). Here the drive estimates the motor speed by analyzing the back EMF voltage. It 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.
AC power
supply
Output
frequency
Output
current
OFF
ON
Starts at the detected speed
Selected
frequency
reference
Min. Baseblock Time
(L2-03)
Several milliseconds
b3 -05 <1>
Figure 5.11 Speed Search after Baseblock
<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.
5.2 b: Application
130
YASKAWA ELECTRIC SIEP C710606 18F YASKAWA AC Drive – V1000 Technical Manual