Inverter low voltage tripping causes
Inverter low voltage mainly refers to the low voltage of the intermediate DC circuit, generally can cause the low voltage of the intermediate DC circuit from two aspects:
1, from the power input side of the low voltage
Under normal circumstances, the power supply voltage 380V, the allowable error is -15% ~ 10%, the voltage value of the intermediate DC after the three-phase bridge full-wave rectification is 513V, and the voltage fluctuation of the power supply line voltage in individual cases is relatively small, which will not cause the inverter to trip the low voltage, and only if the effective value of the power grid voltage is between 80% ~ 85% of the rated value and the duration of more than one cycle, it will cause the inverter action. Low voltage on the input side of the power supply is mainly due to the fluctuation of the grid voltage or the main power line switching, lightning strikes make the power supply sinusoidal waveform amplitude is affected, the power plant itself transformer overload or load imbalance.
2, from the load side of the low voltage
The reasons for this are mainly large equipment startup and application, line overload or startup of large motors. The frequency converter is composed of two parts: the rectifier and the inverter. Through the study of the inverter, inverter low voltage refers to its intermediate DC circuit low voltage (i.e., the inverter input voltage is too low). General inverters are protected against over-voltage, loss of voltage and instantaneous power failure. The inverter of the inverter is divided into two kinds of GTR and IGBT. When the inverter of the inverter is GTR, once the voltage is lost or the power is cut off, the control circuit will stop outputting signals to the driving circuit, so that the driving circuit and GTR will all stop working, and the motor will be in a free braking state. When the inverter is IGBT, the inverter will be allowed to continue to work for a short period of time td after the loss of voltage or blackout, and if the loss of voltage or blackout time totd, the inverter will stop running under self-protection. General td are in 15 ~ 25ms, and the power supply "shaking power" time to are generally more than a few seconds, the inverter will be self-protection to stop running, so that the motor stops running. Therefore, to solve the problem of inverter low-voltage tripping can not start from the inverter inherent time td and loss of voltage time to, but must be able to withstand the amplitude of the buck to start.
inverter low voltage tripping solution:
To solve the problem of inverter low voltage tripping to master two key points:
One is to choose the frequency converter with IGBT inverter parts;.
The second is to choose a large loss of voltage conditions can still work properly in the frequency converter.
The motor can rotate, but the operating current exceeds the rated value, known as overload. The basic reflection of the overload is: although the current exceeds the rated value, but the magnitude of the exceeding is not large, and generally do not form a large inrush current.
Inverter overload tripping causes and inspection methods
The main reasons for inverter overload
1, false action, the current detection part inside the frequency converter fails, and the current signal detected is large, resulting in tripping.
2, mechanical overload, overload is mainly characterized by motor heating, and can be found from the display screen to read the running current.
3, three-phase voltage imbalance, causing a phase of the running current is too large, resulting in overload tripping, characterized by motor heating is not balanced, and can not necessarily be found when reading the running current from the display (because the display only shows a phase current).
Checking method of whether the frequency converter is overloaded
1, check the motor side of the three-phase voltage is balanced, if the motor side of the three-phase voltage is not balanced, then you should check the output of the inverter three-phase voltage is balanced, such as also unbalanced, the problem is within the inverter.
If the voltage at the output side of the inverter is balanced, the problem lies in the line from the inverter to the motor, check whether all the screws at the terminals have been tightened, and if there is a contactor or other electrical appliances between the inverter and the motor, check whether the terminals of the electrical appliances have been tightened and whether the contacts are in good contact condition.
If the motor side of the three-phase voltage balance, you should know the operating frequency at the time of tripping: if the operating frequency is low, and did not use vector control (or no vector control), it is the first to reduce the U/f ratio, if the reduction can still drive the load, then it shows that the original preset U/f ratio is too high, and the peak value of the excitation current is too large, the current can be reduced by lowering the U/f ratio; If the reduction still can not bring the load, then it shows that the original preset U/f ratio is too high, the peak value of the excitation current is too large, and it can be reduced by reducing U/f ratio.
If the load can not be driven after the reduction, the capacity of the frequency converter should be considered to increase; if the frequency converter has the vector control function, the vector control mode should be used.
2, check whether the motor heat, if the motor temperature rise is not high, then first of all should check the frequency converter electronic thermal protection function preset is reasonable, such as the frequency converter still have the capacity, then should relax the preset value of the electronic thermal protection function.
If the temperature rise of the motor is too high, and the overload is a normal overload, then the motor load is too heavy. At this time, the first should be able to appropriately increase the transmission ratio to reduce the load on the motor shaft. If you can increase, then increase the transmission ratio. If the transmission ratio can not be increased, the motor capacity should be increased.