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How to choose IGBT （Insulated Gate Bipolar Transistor）2024-01-10 11:17:26
1. The selection of rated voltage for IGBT: After rectification and filtering of the three-phase 380V input voltage, the maximum value of the DC bus voltage: under the condition of switch operation, the rated voltage of IGBT is generally required to be twice higher than the DC bus voltage. According to the voltage level of IGBT specifications, choose an IGBT with a voltage level of 1200V.
2. Taking a 30kW frequency converter as an example, the selection of IGBT rated current is about 79A. Due to the current overload during electrical startup or acceleration of the load, it is generally required to withstand 1.5 times the overcurrent within 1 minute. The maximum load current is about 119A, and it is recommended to choose an IGBT with a current level of 150A.
3. The selection of IGBT switch parameters: The switching frequency of the frequency converter is generally less than 10kHz. However, in actual operation, the on state loss of IGBT accounts for a relatively large proportion. It is recommended to choose a low on state IGBT.
4. Factors affecting IGBT reliability:
(1) When IGBT operates with gate voltage, there must be a forward gate voltage. The commonly used gate driving voltage value is 15-187, with a maximum of 20V used. The shed voltage is closely related to the gate resistance Rg. When designing IGBT driving circuits, refer to the rated Rg value in the IGBT Datasheet, design appropriate driving parameters, and ensure a reasonable forward gate voltage. https://www.dgdqw.com/wenku/rd/dianzi/ Because the working state of IGBT is closely related to the forward gate voltage, the higher the forward gate voltage, the smaller the turn-on loss, and the smaller the forward voltage drop.
In bridge circuits and high-power applications, in order to avoid interference, a negative voltage is applied to the gate when the IGBT is turned off, usually between -5-15V, to ensure the IGBT's turn off and avoid the influence of Miller effect.
(2) In order to reduce the impact of Miller effect, improvement measures are adopted in the IGBT gate drive circuit:
① Using different gate resistors Rg, ON and Rg, off for turn-on and turn-off to ensure effective turn-on and turn-off of IGBT;
② Add a capacitor c between the gate sources to discharge the energy generated by the Miller effect voltage;
③ Apply negative gate voltage when turning off. In practical design, a reasonable combination of the three is more effective in improving the Miller effect.