An AMF panel is built to the installation, not bought off a shelf. Getting the specification right at enquiry stage saves a rebuild later, and most of it comes down to six numbers.
Start from full-load current
The panel is sized by current, not by kVA. Convert first.
For a three-phase set:
I = (kVA × 1000) ÷ (√3 × V)
A 125 kVA set at 415 V gives (125 × 1000) ÷ (1.732 × 415) = 174 A.
Common ratings at 415 V, 50 Hz:
- 62.5 kVA → 87 A → 100 A changeover
- 125 kVA → 174 A → 200 A changeover
- 250 kVA → 348 A → 400 A changeover
- 500 kVA → 696 A → 800 A changeover
At 480 V, 60 Hz the current is lower for the same kVA, so a set exported to a 60 Hz market may take a smaller device than the same rating at 415 V.
Decide three-pole or four-pole
This is decided by the earthing arrangement, not by preference.
Four-pole switching is required where the neutral must be broken so that only one neutral-earth connection exists at a time. This is normal where the generating set has its own neutral earth.
Three-pole is used where a common neutral is retained between the two sources.
Getting this wrong creates parallel earth paths and defeats the earth fault protection, so confirm the site arrangement before quoting.
Choose the controller
The controller defines what the panel can do:
- Auto start only — the set starts on a signal but transfer is manual
- Auto mains failure — monitors utility, starts, transfers, returns, cools down and stops. A
DSE6020covers straightforward single-set duty; aDSE7320adds more inputs and outputs, richer protection and event logging - Synchronising — required where sets run in parallel with each other or with the mains
Specify the breaking capacity
Breakers must interrupt the prospective short-circuit current at the point of installation. A panel with correctly sized but under-rated breakers is dangerous.
Ask the client for the prospective fault level, or the transformer rating and impedance from which it can be calculated. Where nothing is known, a conservative assumption is made and stated on the quotation.
Account for site conditions
Two conditions commonly force a change to a standard build:
- Ambient temperature above 40 °C requires derating of both the panel components and the enclosure ventilation
- Altitude above 1000 m reduces the cooling effect of air and the dielectric strength between conductors
Both are routine in a good proportion of the markets these panels ship to, so they are worth asking about at enquiry rather than after delivery.
What to send with an enquiry
To quote a panel we need: set rating in kVA, system voltage and frequency, number of phases, three-pole or four-pole, preferred controller, prospective fault level, cable entry direction, and site ambient and altitude if either is unusual.
With those, a quotation follows within one working day.
Questions
What size AMF panel do I need for a 125 kVA generator?
A 125 kVA set at 415 V three-phase draws approximately 174 A at full load, so the changeover device and breakers are normally rated at 200 A, with the breaking capacity selected for the prospective fault level at the installation.
Is an AMF panel the same as an ATS?
No. An ATS only transfers load between two sources. An AMF panel does that and also starts and stops the set, monitors engine parameters and provides set protection. An AMF panel normally contains an ATS or contactor changeover within it.