B3: Speed Search - YASKAWA T1000V Technical Manual

b2-12: Short Circuit Brake Time at Start
■
Short-Circuit braking can be used in Open Loop Vector for PM motors. By shorting all three motor phases it produces a
braking torque in the motor and can be used to stop a coasting motor before starting it.
Parameter b2-12 sets the time for Short-Circuit Brake operation at start. Disabled when set to 0.00 s.
No.
b2-12
■ b2-13: Short Circuit Brake Time at Stop
The Short-Circuit braking described for parameter b2-12 can also be applied at the end of deceleration in order to
completely stop high inertia loads. Short circuit braking is initiated when the output frequency falls below the higher of
the values b2-01 and E1-09.
Parameter b2-13 sets the time for Short-Circuit brake operation at stop. Disabled when set to 0.00 s.
No.
b2-13

◆ 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.
■ 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.
Figure 5.11
<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.
YASKAWA ELECTRIC SIEP C710606 44B YASKAWA AC Drive T1000V Technical Manual
Name
Short Circuit Brake Time at Start
Name
Short Circuit Brake Time at Stop
AC power
supply
ON OFF
Output
frequency
Output
current
Min. Baseblock Time
(L2-03)
Figure 5.11 Speed Search after Baseblock
Starts at the speed
that was detected
Several miliseconds
b3-05 <1>
5.2 b: Application
Setting Range
0.00 to 25.50 s
Setting Range
0.00 to 25.50 s
Selected
frequency
reference
Default
0.00 s
Default
0.50 s
5
115