YASKAWA GA700 Technical Manual page 609

Figure 11.29 Speed Search Selection at Start (Current Detection Type)
Note:
Note the following points when using Current Detection Speed Search.
• Current Detection Speed Search cannot be used with PM motors.
• Speed Search will not be performed if the motor is rotating in reverse.
• Caution should be taken when using Current Detection Speed Search with light loads or a stopped motor, because the motor may
suddenly accelerate.
• Lower the value set in b3-03 if oL1 [Motor Overload] is triggered when executing Current Detection Speed Search.
• Set a higher value in L2-03 if oC [Overcurrent] or ov [Overvoltage] is triggered when executing Current Detection Speed Search after
recovering from a momentary power loss.
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Speed Estimation
This Speed Search function is used with induction motors. Set b3-24 = 1 [Speed Search Method Selection =
Speed Estimation]. This function has the advantage of using less current and a shorter search time. Speed Search
can be performed even if the motor is rotating in reverse. There is no concern of sudden acceleration after power
is restored following a power loss.
Note:
Speed Estimation Speed Search cannot be performed in the following situations. Use Current Detection Speed Search instead.
• When operating multiple motors on a single drive.
• When using a high-speed motor (200 Hz or higher)
• When using a motor 1.5 kW or smaller
• When the motor output is more than 1 frame size smaller than the drive capacity
• When using a long wiring distance between the drive and motor
Speed Estimation Speed Search estimates the motor speed in the following two steps.
1. Residual Voltage Search
The drive searches for residual voltage when there is a short baseblock time. The drive estimates the motor
speed and direction of rotation by the residual voltage in the motor. The drive outputs the motor speed it
estimated as frequency, then raises voltage using the deceleration rate set in L2-04. Once the output voltage
matches the V/f pattern, the drive accelerates or decelerates the motor to the frequency reference. If the drive
is unable to estimate the motor speed due to low residual voltage, then it will automatically execute Current
Injection.
Note:
Once power is restored, the drive waits for the time set in b3-05. If power loss is longer than the time set in L2-03, the drive will begin
Speed Search when the time set in b3-05 has passed after the power recovery.
2. Current Injection
YASKAWA ELECTRIC SIEP C710617 01B YASKAWA AC Drive GA700 Technical Manual
Figure 11.30 Speed Search after Baseblock
11.3 b: Application
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