Verified DG & Generator Control Panel Manufacturers — AMF, Synchronising, Protection

What is an AMF panel and how does it work?

A: An AMF (Auto Mains Failure) panel monitors grid supply voltage and frequency continuously. When mains fail: (1) mains failure is confirmed after a set delay (5–10 seconds, to avoid starting DG for momentary dips), (2) start signal sent to DG, (3) after DG builds up voltage and frequency (30–60 second warm-up), (4) load transfer contactor/ACB opens mains and closes DG — all automatically. When mains return: (1) mains quality is confirmed for a stability delay, (2) load is transferred back to mains, (3) DG cool-down period, then DG stops.

What is open-transition vs closed-transition load transfer in DG panels?

A: Open-transition transfer breaks the old source before connecting the new source — creating a momentary power interruption (typically 100ms–500ms). Suitable for most loads. Closed-transition (make-before-break) briefly parallels both sources during transfer — providing seamless (0ms) power transfer for sensitive loads (servers, medical equipment, industrial processes). Closed-transition requires synchronising between DG and mains before transfer and is significantly more complex and expensive (30–50% premium over open-transition panels).

How many DG sets can be paralleled and what limits the number?

A: Theoretically unlimited DG sets can be paralleled, but practical limits apply. Key constraints: (1) bus bar fault level — total connected kVA determines fault current the bus must withstand, (2) load sharing accuracy — governor and AVR matching across DG sets, (3) synchronising panel complexity — each additional DG adds synchronising channels, (4) protective relay coordination — differential protection becomes complex above 4–5 DGs. Most industrial applications parallel 2–4 DG sets; larger facilities use separate bus sections.

What is reverse power protection and why is it critical for DG sets?

A: Reverse power protection (relay type 32) trips the DG circuit breaker when the DG begins absorbing power from the bus (motoring) instead of supplying it. This occurs when the DG engine fails or under-speeds but remains connected. A DG motoring as an electric motor can destroy the engine and alternator within seconds. Reverse power protection is mandatory for any DG operating in parallel with mains or other DG sets — its absence is a catastrophic design omission.

Can a standard AMF panel be used for solar-DG hybrid systems?

A: Standard AMF panels are designed for grid + DG switching only. Solar-DG hybrid systems require specialised control logic that manages three sources: grid, solar inverter output, and DG. The priority sequence is: solar first (free energy), DG next (backup), grid last (import only when needed). Solar-hybrid control panels must also prevent DG from operating when solar alone can meet the load, and manage bidirectional power flow. Specify "solar-DG-grid hybrid AMF panel" with the hybrid control logic explicitly to your panel manufacturer.