One, parameter description
1. The data given in the parameter table of this manual, ITSM, I2t, dv/dt, and di/dt are the minimum values that the component can satisfy, and the maximum value of Qrr, TQ, VTM, VTO, and rT can be satisfied (not more than).
2. The average current rated current rating IT (AV) (IFAV)
IT (AV) (IF (AV)) means the maximum value of the sinusoidal half wave current that is allowed to flow through the component at the prescribed radiator temperature under the condition of two side cooling. IT (AV) (IF (AV)) corresponds to component rated effective value IRMS=1.57IT (AV). In actual use, if the temperature of the radiator is not below the prescribed value, or the thermal resistance of the radiator and the component is far greater than the prescribed value, the element should be reduced.
3. The rise rate of the thyristor through current di/dt
The critical repetition value for the component on state current rise is given in the parameter table. The corresponding non repetition test value is more than 2 times that of the repeat value. In the process of use, it is necessary to ensure that the current rising rate at any time in the element conduction period must not exceed the repetition value.
4. Use frequency of thyristor
The maximum frequency of the thyristor working is determined by the current pulse width of TP, the turn off time TQ, and the time to start from the positive pressure from the shutdown to its reopening time tV. Fmax=1/ (tq+tp+tV). When selecting the components according to the working frequency, it is necessary to ensure that the components pass from the forward current to zero to the positive pressure interval tH>tq, and leave a certain margin. With the increase of working frequency, component forward loss Epf and reverse recovery loss Epr increase, and component on state current must be reduced.
5, turn off time (TQ)
After the anode current is reduced to 0, if the anode voltage is immediately added to the anode, even if there is no gate signal, it will also be guided again. If the positive anode voltage is added again before the positive anode voltage is added, it will not be misleading, which means that the SCR needs a certain amount of time after the switch off. Restore its blocking ability. The minimum time interval from the current over 0 to the device to block the positive voltage is TQ, which is composed of the reverse recovery time TRR and the gate recovery time, and the TQ of the ordinary SCR is about 150-200 Mu s, which usually satisfies the use of the common frequency converter, but can be used in the case of the large inductive load. Some choices. In the use of intermediate frequency reversal applications, such as intermediate frequency device, motor vehicle chopper, frequency conversion speed regulation, and so on, the switching time parameters must be selected. The closing time of the general fast silicon controlled thyristor (KK type thyristor) is 10-50 U S, and its working frequency can reach 1KHz~4 KHz.
Two. Selection of components
Proper selection of power electronic devices such as thyristor and rectifier tube is of great importance for ensuring the reliability of the whole machine and reducing the cost of the equipment. The selection of components should take into account the factors such as the environment, cooling mode, line type, and load nature, so as to give consideration to the economy under the condition that the parameters of the selected components are abundant. The application of power electronic devices is very wide, and the specific application forms are varied. The selection of the thyristor elements in the rectifier circuit and the single intermediate frequency inverter circuit is explained below.