Question:
How is it possible to switch off the drive controller in case of active current limit control with a TRIP error message not before the frequency has fallen below a set value?
Answer:
Request:
- The drive controller is operated in voltage/frequency characteristic control without feedback.
- In case of an overload the drive controller is not supposed to switch off immediately with an error message, but it should continue operation a long as possible.
- If a current limit control is required for balancing a load, the drive controller is supposed to be interfered not before the frequency has fallen below a set value, and it must reset the signal 'DCTRL1-RDY'.
Control:
- By means of the code C0022/C0023 (I_max-limit) the overload limit is set for the drive controller.
- If the output current of the drive controller reaches the set overload limit, the current limit control will become active. It reduces the drive controller's output frequency as long as its output current falls below the current limit (C0022/C0023). If the frequency falls below a set value before this current limit is reached, a TRIP error massage is to be activated.
Wiring:
- The analog output 2 (X3.2/63) must be connected to the anaolg input (X3.1/2U) by means of a wire bridge.
Parameter setting:
For the parameter set 1:
- Parameter setting of overload limit (I_max): C0022/C0023 = 150 %
- Activation of setpoint source PCTRL1-SET2: C0145 = 1
- Parameter setting of the current threshold for overload detection: C0156 < 150 % (e. g. 140 %)
- Parameter setting of the frequency setpoint for the comparator (PCTRL1-SET2): C0181 = X (e. g. 20 Hz)
- Parameter setting of the comparator's deceleration: C0234 = X (e. g. 0.01 s)
- Parameter setting of the comparator's hysteresis: C0235 = X (e. g. 2 Hz)
- Connection of the signal of the parameter set changeover (DCTRL1-PAR2/4) with the overload detection (DCTRL1-(IMOT>ILIM)-RFG-I=0): C0410/13 = 231
For the parameter set 2:
- Parameter setting of the overload limit (I_max): C2022/C2023 = 150 %
- Connection of the signal DCTRL1-TRIP-SET with the signal PCTRL1-SET=ACT: C2410/11 = 229
- Connection of the signal of the parameter set changeover (DCTRL1-PAR2/4) with the overload detection (DCTRL1-(IMOT>ILIM)-RFG-I=0): C2410/13 = 231
- Connection of the analog input 2 (AIN2-OUT) with the signal PCTRL1-ACT: C2412/5 = 4 (Do not forget the wire bridge -> see 'Wiring')
- Connection of the analog output 2 (AOUT2-IN) with the signal MCTRL1-1/NOUT: C2419/2 = 6 (Do not forget the wire bridge -> see 'Wiring')
Function:
When the current threshold (C0156) is reached for the overload detection the drive controller changes from parameter set 1 to parameter set 2. The current limit control limits the frequency in case of a load. As soon as the frequency depression falls below a defined value (C0181), the drive controller will set an external trip (by DCTRL1-TRIP-SET), the signal DCTRL1-RDY will be reset and the output stages will be inhibited. Consequently, the overload will disappear and the drive controller will change back from parameter set 2 to parameter set 1. After the error has been acknowledged by the user, the TRIP will be deactivated, and the drive controller can continue operating.
