YASKAWA GA800 Series Technical Reference page 953

Principles of Operation
HSB increases motor slip by significantly decreasing the frequency supplied to the motor at the same time that
deceleration starts. A large quantity of current flows through the motor to increase the motor loss, and the motor
decelerates while the motor windings consume the regenerative energy.
The drive keeps the motor current at a constant level during deceleration to prevent overvoltage and do automatic
braking and it also keeps a slip level that causes the maximum quantity of deceleration torque.
High Slip Braking Precautions
• Do not use the high slip braking function in these applications:
– Frequent deceleration
– Deceleration time differences
– Continuous regenerative loads
– It is necessary to accelerate again during deceleration
• Motor loss increases during high slip braking. Use this function when the duty time factor is 5% ED or less and the
braking time is 90 seconds or less. The load inertia and motor characteristics have an effect on the braking time.
• The drive ignores the configured deceleration time during high slip braking. To stop motors in the configured
deceleration time, set L3-04 = 4 [Stall Prevention during Decel = Overexcitation/High Flux].
• You cannot use high slip braking to decelerate deceleration at user-defined speeds. To decelerate at user-defined
speeds, use the overexcitation deceleration function.
• You cannot accelerate the motor again during high slip braking until you fully stop the motor and input the Run
command again.
• You cannot use high slip braking and the KEB Ride-Thru function at the same time. If you enable those two
functions, the drive will detect oPE03 [Multi-Function Input Setting Err].
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Overexcitation Deceleration
Overexcitation deceleration quickly decelerates motors without braking resistors. This lets you stop a motor more
quickly than with the ramp to stop processes.
Overexcitation deceleration increases excitation current during deceleration to cause a large quantity of braking
torque through motor overexcitation. You can set the deceleration speed to adjust the deceleration time for
overexcitation deceleration.
Overexcitation deceleration lets you accelerate the motor again during deceleration.
Enter the Run command during overexcitation deceleration to cancel overexcitation deceleration and accelerate the
drive to the specified speed.
To enable this function, set L3-04 = 4, 5 [Stall Prevention during Decel = Overexcitation/High Flux, Overexcitation/
High Flux 2].
When L3-04 = 4, the motor will decelerate for the deceleration time set in C1-02, C1-04, C1-06, or C1-08. If the
drive detects ov [Overvoltage], increase the deceleration time.
When L3-04 = 5, the drive uses the value in C1-02, C1-04, C1-06, or C1-08 to decelerate and it adjusts the
deceleration rate to keep the DC bus voltage at the level set in L3-17 [DC Bus Regulation Level]. The load inertia and
motor characteristics have an effect on the braking time.
Notes on Overexcitation Deceleration
• Do not use Overexcitation Deceleration with a braking resistor.
• Do not use Overexcitation Deceleration for these applications. Connect a braking resistor to the drive as an
alternative to Overexcitation Deceleration.
– Frequent sudden decelerations
– Continuous regenerative loads
– Low inertia machines
– Machines that have no tolerance for torque ripples
• Motor loss increases during overexcitation deceleration. Use this function when the duty time factor is 5% ED or
less and the braking time is 90 seconds or less. The load inertia and motor characteristics have an effect on the
YASKAWA SIEPC71061737B GA800 Drive Technical Reference
12.10 n: Special Adjustment
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953