Overload is one of the more frequent faults in the frequency converter trip. Overload faults include variable frequency overload and motor overload, which may be caused by too short acceleration time, excessive DC braking, too low grid voltage, and excessive load. Generally, it can be solved by extending the acceleration time, extending the starting time, checking the grid voltage, and the like. Usually see the overload phenomenon, in fact, we should first analyze whether the motor is overloaded or the inverter itself is overloaded. Generally speaking, due to the strong overload capability of the motor, as long as the motor parameters of the inverter parameter table are properly set, overload is generally not expected. The inverter itself is prone to overload alarms due to its poor overload capability. We can detect faults such as inverter output voltage and current detection circuit to eliminate faults. Main cause of overload
(1) The main feature of excessive mechanical load is that the motor is hot and can be found by reading the operating current from the display.
(2) Three-phase voltage imbalance causes the running current of a certain phase to be too large, resulting in overload tripping. It is characterized by uneven heating of the motor. It is not always found when reading the running current from the display screen (since the display only shows one phase) Current).
(3) The current detection part inside the inverter that malfunctions fails, and the detected current signal is too large, causing a trip.
Troubleshooting method for checking method overload(1) Check if the motor is hot
If the temperature rise of the motor is not high, first check whether the electronic thermal protection function of the inverter is preset properly. If the inverter still has a margin, the preset value should be relaxed; if the allowable current of the inverter has no margin , can not be relaxed, and according to the production process, the overload occurs is a normal overload, it means that the selection of the inverter is not appropriate, should increase the capacity of the inverter, replace the inverter. This is because, when the motor is dragging the variable load or the intermittent load, as long as the temperature rise does not exceed the rated value, it is allowed to be overloaded for a short time (a few minutes or tens of minutes), and the inverter is not allowed. If the temperature rise of the motor is too high and the overload that occurs is a normal overload, it means that the load of the motor is too heavy. At this time, first consider whether the gear ratio can be appropriately increased to reduce the load on the motor shaft. If it can be increased, increase the transmission ratio; if the transmission ratio cannot be increased, increase the capacity of the motor.
(2) Check if the three-phase voltage on the motor side is balanced
If the three-phase voltage on the motor side is unbalanced, check whether the three-phase voltage at the output of the inverter is balanced. If it is not balanced, the problem is inside the inverter. The inverter module of the inverter and its drive circuit should be checked.
If the voltage at the output of the inverter is balanced, the problem is that the screws from all the terminals are tightened on the line from the inverter to the motor. If there is a contactor or other electrical device between the inverter and the motor, check that the terminals of the appliance are tight and that the contact is in good condition.
If the three-phase voltage on the motor side is balanced, the operating frequency at the time of tripping should be known: if the operating frequency is low and vector control is not used (or no vector control), the U/F ratio is first reduced; if it is reduced, the load can still be driven. , the original U/F ratio is too high, the peak value of the excitation current is too large, the current can be reduced by reducing the ratio of U/F; if the load is reduced after the reduction, the inverter should be considered. Capacity; if the frequency converter has vector control, vector control should be used.
(3) Check if it is malfunctioning
If the cause is not found after the above inspection, it should be checked whether it is a malfunction. The method of judging is to measure the output current of the inverter with an ammeter under light load or no load, and compare it with the running current value displayed on the display. If the current reading displayed by the display is larger than the actual measured current. If there is more, it means that the current measurement part of the inverter has a large error, and the "overload" trip may be a malfunction.
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