YASKAWA OYMC V1000, Programming Manual

Page: 50 / 408

1.2 b: Application
50 YASKAWA ELECTRIC SIEP C710606 10A YASKAWA AC Drive - V1000 PRELIM. Programming Manual
◆
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.