Abstract
The study showed that we can implement the principle of current control of the main circuit of a hybrid DC contactor by introduction of a small-size transformer of current into it. It has two primary windings, the first of which is connected to the first pole in succession with the main contact, the second one ‒ in series with a semiconductor switch, which shunts this contact in opposition to the first, and one secondary power supply. The study determined peculiarities of the processes of current flowing from the circuit of the main contacts, the commutation of a current transformer, the charging of a commutation condenser for locking of a semiconductor switch. The study showed that a magnetic wire conductor of a transformer is saturated and a control circuit is deenergized in a switched-on state. When a contactor is switched off, the charge of a commutation condenser capacitor goes due to a direct current under an action of EMF, which occurs on the secondary winding of a transformer during its re-magnetization in the opposite direction by current flowing in a shunting circuit. At the same time, at the given values of a cross section of a magnetic conductor and capacity of a condenser, a voltage level to which it is charged, does not depend on the number of turns of the secondary winding, but it is proportional to a square root of commutated current. The time of its charge under the same conditions is proportional to the number of turns of the secondary winding. This makes it possible to approach reasonably definition of parameters of elements that provide reliable locking of semiconductor switchers. The study showed that the proposed hybrid contactors, due to introduction of circuit current control, have properties that enhance their competitiveness compared to the existing ones. Specifically, they increased reliability, they do not need a power supply from an additional power source, they exclude standard drivers, they show minimized energy consumption. Thus, the application aspect of a use of the obtained scientific result is the possibility of creation of competitive reliable hybrid DC contactors for voltage up to 1,000 V and currents of 100‒630 A
Highlights
Hybrid contactors, first developed in the 1970s, were designed for currents of 100‒630 A and voltage up to 660 V for circuits of alternating current, and for currents of 600‒630 A and voltage up to 440 V ‒ for DC circuits.The developed contactors surpassed classical electromagnetic contactors by 20‒25 times by switching durability but underperformed significantly in terms of cost and weight-dimensional parameters
We should note that hybrid DC contactors did not gain much demand in the market of electrical products due to their relatively high cost, large size and weight, due to the existence of a complex system of forced commutation
Main contacts are connected to a power IGBT transistor in parallel
Summary
The developed contactors surpassed classical electromagnetic contactors by 20‒25 times by switching durability but underperformed significantly in terms of cost and weight-dimensional parameters Such contactors were technically and economically feasible to apply only for difficult operating modes. Only elaboration and dynamic development of fully controlled integrated power semiconductor devices (SDs) created real prerequisites for further successful development of hybrid commutation devices, in particular hybrid DC contactors. Devices such as dual-operation thyristors of modular constructions (GTO and GCT), powerful transistors and field transistors of IGBT, IEGT, MCT, other types can switch megawatt power flows without the above-mentioned forced commutation systems. The study should focus on the creation of more advanced hybrid commutation devices of direct current
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