●●●I urgently need to know what it means when the circuit trips due to difficulties in pushing coke●●●
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This post was last edited by Wulongdao on 2009-5-16 09:06. Experts, please provide an explanation. Recently, a strange phenomenon has occurred in our workshop: the size of the coal cakes seems to be fine, the temperature is acceptable as well, and the current level isn’t high either – it reaches at most 150. Yet it’s not possible to push the coke forward. Some people say it’s due to a circuit interruption; I’m not sure what exactly causes this circuit interruption. On several occasions, the system trips after pushing the coke forward for just over 1 meter, and it also trips when trying to retract the coke pushing rod after starting up. Could it be a problem with the frequency converter? How can this difficulty in pushing the coke be resolved? We don’t understand this new thing called frequency conversion; we urgently need the help of experts.
If it was working properly before and only started having the above issues recently. Possible faults are as follows: (1) One of the rectifier modules in the inverter is faulty; the other two rectifier modules then drive the inverter module to generate output. Although it can still operate, the inverter’s load-carrying capacity is significantly reduced. When driving a normal load, the normal rectifier modules may experience overcurrent and trigger a protective shutdown. ⑵If one of the drive control boards that regulate the conduction and output of the rectifier module or inverter module is damaged, the same situation as described above will occur. Please have the technical staff from the inverter manufacturer conduct a comprehensive test and diagnosis; if the aforementioned fault is confirmed, the damaged components need to be replaced.
Recently, our company has also encountered difficulties in pushing coke due to low current levels, and the cause cannot be identified. We would appreciate your advice!
Was it a power outage due to frequency variation or a circuit breaker tripping?
When an inverter trips, a fault message will be displayed; you should investigate the issue based on this message, as only by knowing the nature of the fault can you analyze it properly. I think it’s likely that the torque of the motor is insufficient. At low speeds, the voltage of the motor is controlled by the inverter; to achieve a certain level of thrust, it’s necessary to increase the current. However, when the current rises too high, it reaches the set value for motor protection, resulting in a shutdown. At this point, it is possible to increase the torque boost value (that is, to raise the output voltage of the inverter at the same frequency), but be aware that the motor’s temperature will rise rapidly in this case, so proper cooling is necessary. Another method is to increase the reduction ratio of the transmission mechanism, which can also achieve the same goal.
What model is the frequency converter? I recommend setting the torque compensation to automatic and changing the drive control mode to vector control, in order to achieve high dynamic response and high starting torque performance. Additionally, the low current value you mentioned may be due to the ammeter or current meter you are using being affected by the inverter, resulting in inaccurate readings; the current value shown by the inverter should be taken as the accurate figure.
I agree with the moderator’s analysis and judgment. However, the torque increase should be done gradually; if it is increased too much, magnetic saturation will occur, leading to overcurrent. Modern frequency converters generally come equipped with vector control functionality, which can increase the starting torque of the motor. In my experience, using vector control yields better results.