Transfer switch

A source-transfer switch is a switching device that transfers the electrical load from a main power supply to a backup source. Socomec's ATyS range covers ratings from 25 A to 6300 A in manual, motorised and programmable automatic versions. This equipment complies with IEC 60947-6-1 and is used to maintain continuity of supply in critical infrastructure.

Types of source-transfer switch and control modes

Manual switching for one-off operations

The manual COMO, SIRCO and SIRCOVER transfer switches suit transfers carried out by an operator on site. Our installation experience confirms that this solution remains relevant for low-criticality networks or periodic generator-set testing. Direct operation gives full control over the transfer without dependence on an electronic control chain.

Motorised and automatic transfer switches for remote switching

The motorised ATyS d versions accept remote commands for transfer operations without human presence. The programmable automatic ATyS M, ATyS S, ATyS G and ATyS p models manage switching autonomously according to configured parameters. Our installation feedback shows that this equipment significantly reduces response time in the event of a network failure.

Ranges and ratings available for ATyS source-transfer switches

Rated current range and installation formats

The range extends from 25 A to 6300 A to cover the full range of low-voltage switchgear needs. The most common ratings are available in a modular version for compact mounting in electrical panels. Our commissioning tests show that this modularity makes integration into extensions of existing installations easier.

Materials and construction of the switching devices

The body of the transfer switches uses reinforced polyamide, providing mechanical strength and resistance to thermal stress in the panel. Silver-plated copper contacts guarantee electrical conductivity and limit erosion wear at high current levels. In the field, we observe that this design withstands the repeated switching cycles inherent in automatic backup applications.

Applications and regulatory compliance of source-transfer switches

Installation sectors and continuity of supply

Source-transfer switches equip data centres, public buildings and critical infrastructure where any supply interruption is unacceptable. Switching to a generator set is carried out within times compatible with upstream UPS ride-through. Our standard practice favours the automatic version when the supported load exceeds several hundred kilowatts.

Applicable standards and safety references

Compliance with IEC 60947-6-1 confirms the breaking capacity and short-circuit withstand of transfer switches. Installation in France also references NF C 15-100 for personal protection and outgoing-circuit selectivity. We recommend checking coordination between the source-transfer switch and the upstream circuit breakers when sizing the installation.

Frequently asked questions

What is the difference between a manual source-transfer switch and an automatic one?

The manual transfer switch requires an operator to actuate the transfer mechanism, whereas the automatic transfer switch detects the network failure and triggers switching without human delay. The choice depends on the installation's criticality level and whether qualified staff are permanently present on site.

How should a source-transfer switch be sized in an electrical panel?

The transfer switch's rated current must exceed the installation's maximum operating current, with a margin to allow for harmonics and motor start-ups. The modular version integrates into sealed enclosures or distribution panels depending on the available space and the rating chosen.

Does a source-transfer switch replace a protective circuit breaker?

No, the source-transfer switch performs the switching function between two power supplies but is not an overcurrent protective device. It must be paired upstream with circuit breakers or fused switch-disconnectors in line with NF C 15-100 requirements.

Which standard applies specifically to source-transfer switches in France?

IEC 60947-6-1 defines the operating rules and tests for transfer switches, while NF C 15-100 governs their implementation in French low-voltage electrical installations. Coordination between these two references guarantees personal safety and continuity of service.