B3: Speed Search - YASKAWA V1000 Technical Manual

No.
b2-12
n 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
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.
<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.
YASKAWA ELECTRIC SIEP C710606 16C YASKAWA AC Drive – V1000 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
125