What is an AMF panel?

 We focus our attention on generator control panels suitable for standby generators.

Navigating through the internet you will find some 'Frequently Ask Questions' about a generator control panel (FAQ). The basic keywords are something like these: What is AMF panel...What size generator to power a house. How much power does a house use. How to connect a portable generator to a house. Connecting Generator to home power. How to use generator to power house. What is a generator control panel...I try to clarify some of the common questions about generators.  First of all: what an AMF Panel is. An AMF control panel (Automatic Mains Failure control panel) is the ideal choice in cases where you have to control a generator that is connected to the Mains in a standby configuration. The AMF control panel is fitted with an AMF controller that manages, in a fully automatic way, the connection assignment of the LOAD to MAINS or GENERATOR avoiding connection MAINS to GENERATOR.  The panel includes miscellaneous equipment:  battery charger, electronic circuit boards,  power relays  and terminal blocks. The AMF  controller is conveniently tasked with driving the power circuit breakers. The size of the circuit breaker capacity and wires defines the required power rating of the panel.  






Available sizes on the market are normally in the range 25-500kVA.  A normal house or big villa needs as much as 9kVA of power. This means the following utilities working simultaneously: 1 fridge, 1 air conditioner (or an electric heater), some lights, an oven,  some tools for D.I.Y., 2 computers, 1 TV set an so on. A 10kVA control panel can fit in a plastic that aesthetically complies with your electrical installation.   A qualified electrician can install the panel in a few hours. We do not recommend to practice D.I.Y. with electric panel and generator. Once the panel is in place you can connect a portable generator also. A small factory needs as much as 80kVA. A small industry up to 500kVA.

On the left an internal view of a 30kVA AMF control panel equipped with BeK3 AMF controller. You can observe

[1] POWER SUPPLY CONNECTION. The AMF controller is supplied by the battery of the engine. The controller can work in the range 6 up to 36VDC. The AMF controller is very well protected against spikes generated by switching heavy inductive load during the start and stop sequences of the engine.

[2] RS485 SERIAL INTERFACE CONNECTION. The controller supports the MODBUS protocol that will allow you to control and monitor the generator from a remote location.

[3] CANBUS SERIAL INTERFACE & CONFIGURABLE INPUTS. The BeK3 controller is a very flexible controller able to operate with any kind of engine. You can use a SAEJ1939 compatible engine or standard (mechanical regulation) engines. The controller interfaces with resistive sensors.


[4] GENERATOR VOLTAGE & MAINS VOLTAGE CONNECTIONS. The controller works in a 3-phase configuration up to 600Vac permanently. Protection fuses are required to protect the cables. Controller inputs feature high impedance (about 2 Mega Ohm).

[5] REAR COVER GROUND CONNECTIONS. The controller is protected by a special steel cover. This protects the controller from electromagnetic fields generated by switching the MAINS & GENERATOR circuit breakers.


[6] CURRENT TRANSFORMER CONNECTIONS. In order to protect  the all system from overload, these transformers provide current measurements to the AMF controller.

[7] CONFIGURABLE OUTPUT CONNECTIONS. Allows the controller to configure outputs via programmable options. There are more than 80 options for each programmable output.


In this example a rear view of the most simple single phase AMF controller: the BE21. [4] door lock [5] Emergency switch. CUT-OUT about 190x93 (mm). Also required, for this controller, four M4 holes to hold the controller in place.


You install the Be242 controller on the frontal door without cutting out the rectangular hole to insert the controller. The Be242 contains all printed circuit boards and connections for the entire AMF panel. A traditional AMF controller may require 50 meters of cables and up to 100 connections. The Be242 is a multiprocessor system. A micro controller manages the inputs, another one make the measurements, another controle the outputs. The system intelligently shares a cloud of common software resources. You do no longer need to connect an alarm switch to the panel and then to the controller! You connect the alarm to the panel. That's it! The point of connection, being intelligent, communicates directly wireless with the AMF controller.

SAVE AT LEAST 30 METERS OF CABLE FOR EACH AMF PANEL The controller reads  all electrical parameters (V-A-KW-KVA-KVAR-PF-KWH) via wireless sensors in the panel or generator. 

FRONTAL DOOR MOUNT  WITHOUT "SQUARE CUT-OUT"   Make a 22mm round hole for the IP65 supply connector and a 2x4mm holes to securely fix the controller to the door. Not having a cut-out, the door makes an extraordinaly job in EMC filtering.

SAVE 2 HOURS LABOR WORK, ASSEMBLE A PANEL IN 30 MINUTES You are no longer required to connect hundreds of terminal blocks and wires. The user will connect the generator & engine directly to the plug-&-play I/O modules.

 IP65 INGRESS PROTECTION & -30° / +70°C OPERATING RANGE A silicon gasket uv-resistant guarantees an IP65 ingress protection. The BE242 controller can operate in harsh environments.


  In the following videos you are going to see the main features of an AMF control panel. The AUTO mode is the most interesting part of it. The main AMF controller duty is to continuously monitor the status of the MAINS. The AMF controller allows you to set low/high limits for Mains Voltage and Frequency. You can program limits for the difference of voltage between phases. You can set a preferential phase rotation as well (CW or CCW). Additionally, you can set a limit of power. In other words you can disconnect the load from the MAINS when the request of energy rises above a certain limit. All these parameters, together with a set of adjustable timers,  are compared with the status of the Mains. When the  AMF controller fitted into the AMF control panel will find an abnormal situation (for a defined period of time), the AMF control panel will disconnect the load to the Mains. This helps prevent a severe damage to your load. Then, if the failure persists for over the programmed time, the AMF control panel will start the engine of your emergency generator. The AMF control panel  will check the quality of the generator electrical parameters (again here you can set limits on several parameters). Once detected that the parameters are within the allowed limits, the AMF control panel  will close the generator circuit breaker. In case of prolonged power outages, your load is safely supplied by your emergency generator and the AMF control panel  continuously monitor the system. You can set limits of load or current in order to prevent overloading of your generator. The AMF control panel as mentioned above does not forget to monitor the Mains! So, when the Mains parameters will return within the programmed settings, the AMF control panel will transfer the load to MAINS. This will happen after a delay that will ensure that the Mains is in stable conditions. Once your load is connected to the Mains, the engine will run for a programmable time (so called COOLING DOWN TIME) without load. After the cooling down time the engine will stop and the AMF control panel is ready for a new power outage.


On the left side a basic wiring diagram of an AMF control panel is provided.

On the removable connector JC you are required to connect the relays. The Bek3 provides a common supply rail (JC8). It is about a dc supply suited for automotive relays that includes over voltage protection, short circuit protection and EMI protection. You are required to use 90-200 OHM dc coil relays (12 V or 24V according to your engine battery).


To a removable connectors JP and JL you will connect the CURRENT TRANSFORMERSsuited for the current monitoring of the EARTH FAULT and 3-PHASE GENERATOR. A /5 transformers are required in the range 50 up to 9900Amps.The JA removable plug is used to monitor the Mains & Generator voltage / frequency in the range 80-600V and 20-99HZ. The version BeK3-400Hz is normally available for Aircraft Ground Support equipment.


The connector JF is used for the ANALOG and DIGITAL sensor fitted on the engine. Terminals for CANBUS are provided on this connector also (your ECU must be SAE J1939 compliant).

The small removable plug JG allows you the connection of the RS485 serial interface that supports the MODBUS protocol. The internal driver will allow you to use a 1000 m cable long.

Watch the video about Bek3 AMF controller presentation

Watch the video about AMF control panel GSM monitoring




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