On the 9300 vector / hoist, what causes a OC3 TRIP and how does clamp mode work?
Answer:
Clamp mode:
If the output current exceeds the clamp current I_clamp = 2.25 * IN_controller, a software clamp is triggered:
The controller sets a brief pulse inhibitor so that the motor current can drop in relation to the inductance in the motor circuit.
After a fixed time (62.5 µs or 250 µs depending on the operating mode and operating frequency) the pulse inhibitor is cancelled and the current can rise again under certain circumstances and trigger another software clamp.
OC3 TRIP:
Every clamp causes the clamp counter to increase by one. If there is no clamp for 2 s, this counter is reset to zero. If the counter reaches the value of 4300, an OC3 TRIP is triggered.
Information about drive selection for short-time load surges and ramp operations: Clamp mode constitutes a permissible operating mode. However, since the drive controller repeatedly set a pulse inhibitor, the drive power available is not optimal. The optimum output power can be taken from the inverter if the output current is just below the clamp threshold.
The illustration below shows the motor current in clamp mode during a ramp operation under a very high load (recorded by the internal oscilloscope of the 9300 vector / hoist).
