Omron SX-F, Инструкция по эксплуатации

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Load Monitor and Process Protection [400]
Section 7-5
7-5 Load Monitor and Process Protection [400]
7-5-1 Load Monitor [410]
The monitor functions enable the VSD to be used as a load monitor. Load
monitors are used to protect machines and processes against mechanical
overload and underload, such as a conveyer belt or screw conveyer jamming,
belt failure on a fan or a pump dry running. The load is measured in the VSD
by the calculated motor shaft torque. There is an overload alarm (Max Alarm
and Max Pre-Alarm) and an underload alarm (Min Alarm and Min Pre-Alarm).
The Basic Monitor type uses fixed levels for overload and underload (pre-)
alarms over the whole speed range. This function can be used in constant
load applications where the torque is not dependent on the speed, e.g. con-
veyor belt, displacement pump, screw pump, etc.
For applications with a torque that is dependent on the speed, the Load Curve
monitor type is preferred. By measuring the actual load curve of the process,
characteristically over the range of minimum speed to maximum speed, an
accurate protection at any speed can be established.
The max and min alarm can be set for a trip condition. The pre-alarms act as
a warning condition. All the alarms can be monitored on the digital or relay
outputs.
The autoset function automatically sets the 4 alarm levels whilst running:
maximum alarm, maximum pre-alarm, minimum alarm and minimum pre-
alarm.
Fig. 49 gives an example of the monitor functions for constant torque applica-
tions.