u
Current Limit
This function provides a current limit of the pump (motor). The function is designed to prevent long-term overload conditions
of the pump, especially if the motor and drive are oversized compared to the pump. The drive will attempt to limit the output
current by reducing the frequency reference. The frequency is reduced using an internal current PI regulator. When the Current
Limit function is active, the alarm "Current Limit Foldback" will be displayed on the HOA keypad. This function will only
operate correctly when the drive is connected to a variable torque motor load such as a centrifugal pump. More specifically,
it will only operate if the load is such that output current increases as output frequency increases (and vice-versa). The current
limit function reduces the pump speed to just above the lower value between the minimum pump speed (P1-06) or the minimum
output frequency. If PI mode is enabled (b5-01 > 0), a special limit will be applied to the PID integrator when output current
limit is active to prevent integrator wind-up.
n
Start Up Procedure
1.
Set all other parameters required for the application such as PI control loop, sleep, motor, and I/O parameters
2.
Turn on the current limit function by setting Q3-01 to 1 (enabled). The default setting is 0 (disabled).
3.
Set the desired current limit in Q3-02. This value should not exceed the motor, pump or drive’s ratings. This does not
in any way change the motor (oL1) and inverter (oL2) overload functions.
4.
If desired, program a multi-function digital output (H2-
oo
) to 89 (Output Current Limit) to annunciate the alarm.
n
Related Parameters
No.
Parameter Name
Setting Values
Q3-01
Output Current Limit Select
Default: 0
Range: 0, 1
Q3-02
Current Limit
Default: 0.0 A
Minimum: 0.0
Maximum: 1000.0
H2 Multi-Function Digital Output Settings
H2-
oo
Setting
Function
Description
89
Output 1 Limit
Closed: Drive output speed is being limited due to the output current limit or the single phase foldback
regulator.
The drive displays an alarm on the keypad when the drive is in output current limit.
HOA Keypad Display
Minor Fault Name
Current Limit
Foldback
Current Limit Foldback
Cause
Possible Solution
Drive output speed is being limited due to
the output current limit.
• Reduce the load.
• Verify setting of Q3-02.
• Change to a larger drive size.
4.6 U1000 iQpump Presets and Functions
YASKAWA TOEPYAIUPW01A YASKAWA AC Drive - U1000 iQpump Matrix Drive User Manual
115
4
Start-Up Programming & Operation