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 1 for more information.
Table 1. 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
|
|
b3-06 [Speed Estimation Current Level 1]
|
x
|
-
|
|
b3-07 [Speed Estimation Current Level 2]
|
x
|
-
|
|
b3-08 [Speed Estimation ACR P Gain]
|
x
|
-
|
|
b3-09 [Speed Estimation ACR I Time]
|
x
|
-
|
|
b3-10 [Speed Estimation Detection Gain]
|
x
|
-
|
|
b3-14 [Bi-directional Speed Search]
|
x
|
x
|
|
b3-17 [Speed Est Retry Current Level]
|
x
|
x
|
|
b3-18 [Speed Est Retry Detection Time]
|
x
|
x
|
|
b3-19 [Speed Search Restart Attempts]
|
x
|
x
|
|
b3-24 [Speed Search Method Selection]
|
x (1)
|
x (2)
|
|
b3-25 [Speed Search Wait Time]
|
x
|
x
|
|
b3-26 [Direction Determination Level]
|
x
|
-
|
|
b3-29 [Speed Search Back-EMF Threshold]
|
-
|
-
|
|
b3-31 [Spd Search Current Reference Lvl]
|
-
|
x
|
|
b3-32 [Spd Search Current Complete Lvl]
|
-
|
x
|
|
b3-33 [Speed Search during Uv Selection]
|
x
|
x
|
|
b3-54 [Search Time]
|
-
|
-
|
|
b3-55 [Current Increment Time]
|
-
|
-
|
|
b3-56 [InverseRotationSearch WaitTime]
|
-
|
x
|
Note:
-
To use Speed Estimation Speed Search with V/f Control, do Rotational Auto-Tuning before you set the Speed Search function. If the wire length between the drive and motor changed since the last time you did Auto-Tuning, do Stationary Auto-Tuning for Line-to-Line Resistance process again.
-
If A1-02 = 5, 6 [PM Open Loop Vector, PM Advanced Open Loop Vector] and the wiring distance between the motor and drive is long or if the motor is coasting at more than or equal to 120 Hz, do not use Speed Search to restart the motor. Use Short Circuit Braking.
Current Detection 2
Use this Speed Search function with induction motors. Set b3-24 = 2 [Speed Search Method Selection = Current Detection 2]. Current Detection Speed Search injects current into the motor to detect the speed of an induction motor. Speed Search increases the output voltage for the time set in L2-04 [Powerloss V/f Recovery Ramp Time], starting from the maximum output frequency or the frequency reference.
Figure 1. Current Detection 2 after Momentary Power Loss
Note:
After you restore power, the drive will not do Speed Search until the time set in b3-05 [Speed Search Delay Time] expires. This means that the drive will not always start Speed Search when the time set in L2-03 [Minimum Baseblock Time] expires.
If you enter the Run command at the same time as Speed Search, the drive will not do Speed Search until the time set in L2-03 expires. When the value set in L2-03 < b3-05, the drive will use the wait time set in b3-05.
Figure 2. Speed Search Selection at Start (Current Detection Type)
| Warning |
|
Sudden Movement Hazard
Do not do Current Detection Speed Search with light loads or a stopped motor.
If you do Auto-Tuning in these conditions, the motor can suddenly accelerate and cause serious injury or death.
|
Note:
-
You cannot use Current Detection Speed Search with PM motors.
-
If the motor is rotating in reverse, you cannot do Speed Search.
-
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.
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 (120 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:
-
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.
Figure 3. Speed Search after Baseblock
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.
-
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.
Figure 4. Speed Search Selection at Start
Note:
Set the lower limit of the delay time to b3-05 for when Speed Search starts.
Speed Search and Operation Conditions
These conditions apply to Speed Search operation. When A1-02 = 0, 2 [Control Method Selection = V/f Control, Open Loop Vector], set b3-24 [Speed Search Method Selection] before you do Speed Search.
-
Do Speed Search with each Run Command
The drive ignores a Speed Search command from the external terminals.
-
Use an MFDI to do an External Speed Search Command
To use an MFDI to do Speed Search, input the Run command at the same time that terminal Sx set for Speed Search activates, or after Speed Search activates.
Set Speed Search to H1-xx to do the function externally. You cannot set external Speed Search 1 and 2 at the same time.
Table 2. Execute Speed Search via the Digital Input Terminals
|
H1-xx Setting
|
Name
|
Current Detection 2
|
Speed Estimation
|
|
61
|
Speed Search from Fmax
|
ON: Speed Search starts from E1-04 [Maximum Output Frequency].
|
External Speed Search commands 1 and 2 work the same.
The drive estimates the motor speed, then starts Speed Search from the estimated speed.
|
|
62
|
Speed Search from Fref
|
ON: Speed Search starts from the frequency reference immediately before you input the Speed Search command.
|
-
Do Speed Search with Each Auto Restart
Set L5-01 [Number of Auto-Restart Attempts] = 1 or more. After an Auto Restart fault, the drive automatically does Speed Search.
-
Do Speed Search after Momentary Power Loss
Set L2-01 = 1, 2 [Power Loss Ride Through Select = Enabled for L2-02 Time, Enabled while CPU Power Active].
-
Do Speed Search after You Clear the External Baseblock Command
When there is an active Run command and the output frequency is higher than the minimum frequency, you must clear the external baseblock command to do Speed Search.