What is the function of the process overload parameters for the ATV61 and ATV71 series drives?
Resolution:
The Process Overload function in ATV61 and ATV71 drives provides additional process protection by triggering a fault based on user-defined operating conditions rather than the motor's thermal protection limits.
This feature allows the drive to detect abnormal process conditions, such as excessive load, a jammed machine, or slipping equipment, before the motor reaches its rated full-load current.
Parameter Functions
- LOC (Overload Threshold Detection): Defines the current level that will trigger a Process Overload fault. It can be adjusted from 70% to 150% of the motor rated current (NCR). For accurate operation, the NCR parameter should be set to the motor Full Load Amps (FLA).
- TOL (Overload Time Detection): Specifies how long the motor current must remain above the LOC threshold before a fault is generated.
- ODL (Process Overload Fault Management): Determines how the drive reacts when a Process Overload condition is detected.
- SRB (Hysteresis Frequency Attained): Monitors the difference between the speed reference and actual motor speed. A fault is triggered if the motor speed falls below the reference by more than the configured threshold.
Example
Consider a 75 HP motor with a Full Load Amp (FLA) rating of 100 A driving an auger. Under normal operating conditions, the process should require no more than 80 A, even though the motor is capable of drawing up to its rated current.
To protect the process:
- Set LOC = 80% (80 A)
- Set TOL = 2 seconds
- Set ODL = Yes
If the motor current exceeds 80 A for longer than 2 seconds, the drive will generate a Process Overload fault and stop according to the configured fault response.
Using SRB
The SRB parameter can detect mechanical issues such as a jammed machine, stalled motor, or slipping load.
For example:
- Speed Reference = 30 Hz
- SRB = 1 Hz
A fault will occur if the actual motor speed falls below 29 Hz, regardless of motor current.
For additional details, refer to page 212 of the ATV61 Programming Manual (Document 1760649_08).
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Frequently Asked Questions - Schneider Electric (se.com)
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