HE693RTD600 Inverse Parallel Thyristors

HE693RTD600 Two anti-parallel thyristors are connected in series between the motor winding and the power supply. During acceleration to normal speed (ramp start), the motor winding voltage is controlled by means of phase control. The starting torque and starting current of the motor are controlled by controlling the conduction angle of the thyristors. The starting time can also be controlled through the soft starter. Such a short period of time results in a significant temperature increase, e.g. from TStart=40°C to TRamp-up=130°C, resulting in a temperature difference of 90°C for the chip.

The HE693RTD600 current flowing through the semiconductor causes it to consume power, which causes the temperature of the semiconductor to rise, so it must be cooled. In order to avoid the semiconductor still consuming power after the start acceleration process, a mechanical switch is used for bypass. Since there is no need to switch large loads, the bypass switch can be relatively small. Even with a soft starter, the starting current of the system during the start-up phase is still several times the rated current (3-5 times). In high-power systems, the peak starting current often reaches several thousand amperes.

When the HE693RTD600 is used in a soft starter, the semiconductor must be able to withstand considerable variations in chip temperature extremely well and must exhibit good load cycling capability. If these conditions are met, the soft starter will have a long service life. In addition, the compactness and cost-effectiveness of the soft starter are crucial, as the semiconductor must be able to withstand such high starting currents during the start-up phase. At the same time, however, soft starters must be cost-optimised and as compact as possible. Because of this, the size of the semiconductors used, including the heat sink, must be as small as possible.