YASKAWA GA700 Series Technical Manual page 659

Note:
• You cannot use Current Detection Speed Search with PM motors.
• If the drive detects oL1 [Motor Overload] during Current Detection Speed Search, decrease b3-03.
• If the drive detects oC [Overcurrent] or ov [Overvoltage] during Current Detection Speed Search after the drive recovers from a
momentary power loss, increase L2-03.
• If b3-01 = 1 [Speed Search at Start Selection = Enabled], too much current will flow when the motor starts. If there is too much
current at start it will decrease the service life of the drive IGBTs over time.
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Speed Estimation
Use this Speed Search function with induction motors. Set b3-24 = 1 [Speed Search Method Selection = Speed
Estimation]. This function uses less current and has a shorter search time than other functions. This function lets
you do Speed Search when the motor is rotating in reverse. When you return power after a power loss, the motor
will not suddenly accelerate.
Note:
You cannot do Speed Estimation Speed Search in these conditions:
• When You Operate More than One Motor with One Drive
• When you use a high-speed motor (200 Hz or higher)
• When you use a 1.5 kW or smaller motor.
• When the motor output is more than 1 frame size smaller than the drive capacity
• When there is a long wiring distance between the drive and motor
For these conditions, use Current Detection Speed Search.
Speed Estimation Speed Search uses these two steps to estimate the motor speed:
1. Residual Voltage Search
When there is a short baseblock time, the drive searches for residual voltage. The drive uses the residual
voltage in the motor to estimate the motor speed and direction of rotation. The drive outputs the estimated
motor speed as frequency, then uses the deceleration rate set in L2-04 to increase the voltage. When the output
voltage aligns with the V/f pattern, the drive accelerates or decelerates the motor to the frequency reference. If
the drive cannot estimate the motor speed because of low residual voltage, it will automatically do Current
Injection.
Note:
After you return power, 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 start
Speed Search when the time set in b3-05 is expired after the power recovery.
2. Current Injection
If there is not sufficient residual voltage in the motor, the drive does Current Injection. The drive injects the
quantity of DC current set in b3-06 [Speed Estimation Current Level 1] into the motor windings to estimate
the motor speed and direction of rotation. The drive outputs the estimated motor speed as frequency, then uses
the deceleration rate set in L2-04 to increase the voltage. When the output voltage aligns with the V/f pattern,
the drive accelerates or decelerates the motor to the frequency reference.
YASKAWA SIEPC71061705H GA700 Series Technical Manual
Figure 12.31 Speed Search after Baseblock
12.3 b: Application
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