12.3 b: Application
732 YASKAWA SIEPC71061737D GA800 Drive Technical Reference
This function stops and restarts a coasting PM motor. The drive short circuits all the three motor phases to make
braking torque in the motor.
Set this parameter to 0.00 to disable the function.
Note:
• Short circuit Braking will let external forces rotate the PM motor. Use DC Injection Braking to prevent motor rotation from external forces.
• Motor speed and load conditions can make it necessary to install a dynamic braking option on the drive.
■ b2-13: Short Circuit Brake Time @ Stop
No.
(Hex.)
Name Description
Default
(Range)
b2-13
(01BB)
Short Circuit Brake Time @
Stop
Sets the Short Circuit Braking time at stop.
A1-02 = 8: 0.00 s
Other than A1-02 = 8: 0.50 s
(0.00 - 25.50 s)
This function fully stops a PM motor with a large inertia during deceleration and will not let the inertia continue to
rotate the motor.
Short Circuit Braking operates for the time set in b2-13 when output frequency is less than the value set in b2-01 [DC
Injection/Zero SpeedThreshold] or E1-09 [Minimum Output Frequency].
Set this parameter to 0.00 to disable the function.
Note:
Motor speed and load conditions can make it necessary to install a dynamic braking option on the drive.
■ b2-18: Short Circuit Braking Current
No.
(Hex.)
Name Description
Default
(Range)
b2-18
(0177)
Short Circuit Braking
Current
Sets the Short Circuit Braking Current as a percentage of the motor rated current.
100.0%
(0.0 - 200.0%)
The Short Circuit Braking current cannot be higher than the drive rated current, although you can use b2-18 to set a
higher current level. The maximum rated current is 120% when the drive is set for Normal Duty (C6-01 = 1 [Normal
Duty Rating]). The maximum rated current is 150% when the drive is set for Heavy Duty (C6-01 = 0 [Heavy Duty
Rating]).
◆ b3: Speed Search
The Speed Search function detects the actual speed of a coasting motor, then restarts the motor before the motor stops.
Use Speed Search in these conditions:
• To continue operation after momentary power loss
• To switch from commercial power supply to drive power
• To restart a coasting fan
For example, the drive output turns off and the motor coasts when there is a momentary loss of power. After you
return power, the drive does Speed Search on the coasting motor, and restarts the motor from the detected speed.
When you use a PM motor, enable b3-01 [Speed Search at Start Selection].
There are two types of Speed Search for induction motors: Current Detection and Speed Estimation. Use parameter
b3-24 [Speed Search Method Selection] to select the type of Speed Search.
Parameter settings are different for different types of Speed Search. Refer to Table 12.22 for more information.
Table 12.22 Speed Search and Related Parameters
Parameter
Speed Estimation Current Detection 2
b3-24 = 1 b3-24 = 2
b3-01 [Speed Search at Start Selection] x x
b3-03 [Speed Search Deceleration Time] - x
b3-05 [Speed Search Delay Time] x x
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