huaju
2024/03/07
Application and Selection of Pre-charge Resistor and Energy Storage Capacitor in Inverter
The medium and small power general-purpose frequency converter is generally a voltage type frequency converter, which adopts the AC-DC-AC working mode. When the inverter is just powered on, because the filter capacitor capacity on the DC side is very large, the current is equivalent to a short circuit at the moment of charging, and the current will be very large. If there is no charging resistor between the rectifier bridge and the electrolytic capacitor, it is equivalent to a short circuit of 380V power supply directly to the ground, and the instantaneous rectifier bridge will blow up through infinite current. With the current limiting of the charging resistor, if there is no relay or other components, the charging resistor consumes a lot of power. For example, for a 22kW frequency converter, there is at least 45A of current on the PN terminal (DC bus). If there is a problem with the "control circuit" part (such as the quality of relays or thyristors, etc.), the charging resistor will be broken due to too much heat after the inverter runs for a while. Therefore, the charging resistor is connected in series in the charging circuit to limit the current at the moment of energization to protect some input circuit devices such as rectifiers. Some books are also called buffer resistors or starting resistors. SIEMENS 6SE701G variable frequency starting circuit as shown in the figure.
2024/03/07
Taking a pure electric vehicle as an example, this paper introduces the necessity of pre-charging process to alleviate the impact of high-voltage system and improve the safety of the whole vehicle, and elaborates the parameter changes and basis in the pre-charging process, combined with practical experience to provide a reference solution to avoid risks, and finally through the test to prove the feasibility of the method.
2024/03/07
Recently, I came into contact with the matching test of BMS high-voltage distribution box and vehicle functions. Although there were problems of one kind or another, it was also a gain for me. Combined with network resources, I made a little arrangement.
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