• Global Certificate: ISO 9001 : 2015

Relays presentation

current, voltage, differential and on request

Operation principle

Since 1936, Techno-Elec (Servo-Contact) has been the key partner for electrical traction.

The company has designed and manufactured various voltage and current relays, for on-board or fixed equipment. The relays do not need any auxiliary supply and are usually supplied with one normally-open contact (NO) + one normally-closed contact (NC).

Techno-Elec relays operation is based on the principle of electromechanical magnetic circuit. A flow is created in the magnetic circuit thanks to a current which goes through it, a permanent magnet creates an opposite flow which maintains the contacts in the rest position. As soon as the flow of the magnetic circuit overtakes the one of the permanent magnet, the relay triggers and closes.

The moving armature oscillation on a rectified edge, the armature balancing and the use of a permanent magnet as restoring means, ensure a fast commutation without intermediary position. Our contacts with micrometric settings have pushed back the precision limits.


High galvanic separation
No auxiliary supply needed
High reliability, no maintenance needed thanks to the reliable and proven electromagnetic technology
High ability to resist to high overloads

Basic functions

Undervoltage relay
Overvoltage relay
Voltage differential relay
Undercurrent relay
Overcurrent relay
Current differential relay

Examples of applications for on-board equipment

Traction control relay, braking
Traction over-current relay
Detection relay mini voltage catenary
Detection relay maxi voltage catenary
Wheels slip relay
Insulation break relay
Battery control relay
Motor/alternator monitoring relay
Mass relay

Examples of applications in substation

Current detection directional relay (reverse current detection in distribution of electricity)
Catenary voltage detection relay
Mass relay for substation
Current overload relay