The phrase 'dual power supply' covers systems from a small server with two plug-in PSUs to a hospital fed by utility, UPS and generator sources. The core engineering question is not simply whether there are two sources, but whether a single upstream fault can disable both and whether the load can tolerate the transfer interval.

Common architectures

ATS product examples

Nine ATS selection questions

1. What are Source 1 and Source 2: utility, generator, UPS or independent bus?

2. Are the sources truly independent, including switchboard, transformer, cable route and control power?

3. What is the system voltage, frequency, phase arrangement and required pole count? Decide whether the neutral must be switched.

4. What is the continuous current and short-circuit withstand/closing rating at the installation point?

5. How long can the load ride through without power? Compare this with detection, generator start, stabilization and transfer times.

6. Is open transition acceptable, or is closed transition/static transfer required and permitted by the utility and system design?

7. Does the ATS need built-in generator start, voltage/frequency monitoring, programmable delays, communication or remote I/O?

8. How will protection coordinate on both sources, and can a downstream fault remain isolated after transfer?

9. What bypass, isolation, test and maintenance arrangement is required so the ATS is not itself a single point of failure?

Transfer time and load behavior

An electromechanical ATS can transfer quickly, but a utility-to-generator event is usually dominated by generator start and stabilization time. A UPS bridges that interval for zero- or low-interruption loads. Contactors, motors and drives may drop out or restart differently after a transfer, so the sequence must be validated with the actual equipment. A/B server PSUs avoid a source-transfer interruption only when the two inputs and upstream PDUs are independent.

Protection and neutral considerations

• Confirm overcurrent protection and SCCR/withstand on both sources, not only the normal source.

• Decide whether the alternate source creates a separately derived system; this affects grounding and neutral switching.

• Use interlocking and transition logic that prevents unintended source paralleling unless a closed-transition design is specifically engineered.

• Provide monitoring and alarms for source availability, switch position, failed transfer and generator status.

• Include a safe manual or bypass procedure for maintenance and controller failure.

Frequently Asked Questions

What is the difference between dual power and redundant power?

Dual power means two sources are available. Redundancy additionally requires sufficient capacity and independence so one source can fail without losing the load.

Is ATyS g M suitable for a generator?

The product family is presented for automatic transfer and generator applications in the 40-160 A range. Confirm the exact reference, controller features, poles, voltage and local standard.

When would I use SIRCOVER Bypass?

Use a bypass arrangement when maintenance continuity and isolation around the transfer device are required. The switching sequence and interlocks must be engineered.

Does an ATS provide overcurrent protection?

Not necessarily. Some transfer devices are switch-class and depend on external protection; CB-class systems incorporate breakers. Review the exact assembly and standard.

Bottom line

A dual-power system succeeds when the sources are independent, the transfer method matches the load's ride-through capability and protection works on both paths. Model selection then follows current, poles, voltage, ATS class, controller functions and bypass needs.

For an ATS shortlist, send ASBEAM a one-line diagram, source types, voltage, full-load current, pole/neutral requirement, transfer-time target and communication needs.

Technical references

• ASBEAM - Socomec ATyS g M

• ASBEAM - Socomec ATyS S

• ASBEAM - Eaton MATS-G40/4

ASBEAM - Socomec SIRCOVER Bypass