Scientific paper ID 2178 : 2021/2

Contactless logical elements were first developed about 1954-1955, in the USA. This report provides a circuit design for a contactless logical element made with semiconductors, which can be used in both the auxiliary electric circuits of the electric public transport, as well as in its command and control circuits.

The electric transport vehicles (ETV) manufactured before 1990 vastly employ electromechanic contact systems, which tend to be quite problematic for exploitation and maintenance today. The rail and road worthiness of ETV is a key indicator for the quality of the transport service, which predetermines its significance, whereby, ways for its further improvement are constantly being sought.

There are contactless elements for alternating current and voltage based on thrystor technology, which are hard to use in EPT auxiliary circuits due to the complexity in the commutation of direct current and voltage, which operate the auxiliary circuits of modern ETV. The circuit proposed in the report is applicable, and accomplished based on the voltage and current values in the auxiliary circuits of ETV powered on 24VDC, with commuting currents and voltages of up to 20A and 60VDC.

Although the report dwells on a specific control and safety circuit design for tram motrice (TM), Ве4/6S, the same circuit for contactless logical elements can be used in all ETV with auxiliary circuits on standard voltages.

For the purposes of modernisation, a module segment was selected from the block circuit of БУ C0805, which is in charge of the main voltage control and safety function in the control panel and of the voltages for the auxiliary demands of ТМ Ве4/6S, with a contact system controlled by one coil.