• Electrical panels are really control points for electricity.electric panel image by DXfoto.com from Fotolia.com
  
  Every house or building that uses electricity has an electrical panel, also called a service panel. A panel is the place where power comes into, and is distributed throughout, the building. (See reference 1) Aside from being a distribution point, it is usually a central control point. For a home, the panel is relatively simple. For a large automated manufacturing facility, these panels are extremely complex, housing industrial controllers. (See note 1)
  
  

Case

• A panel has a case or housing. The case is what supports the internal components. The panel usually has insulated parts, so no short circuits are created inside the panel itself. A door is installed in front of the panel. Many doors have an opening to place a lock, so no unauthorized entry is permitted. Only authorized personnel is allowed to open the door.
  
  

Main Disconnect

• When the power comes into the panel, it first goes through the main disconnect. The main disconnect is both a breaker and an on-off switch. If the panel has to be disconnected from the incoming power, the main disconnect lever is pushed to the "Off" position. If the building experiences a huge power surge, due to a short or overload, the main disconnect trips to the "Off" position, saving the building's electrical system. (See note 1)
  
  

Breakers

• After the electricity runs through the main disconnect, it is fed out to the individual breakers. Breakers are really on-off switches that can be turned off by the user or turned off automatically. Breakers are designed to be the weakest point in a circuit, much like the weakest link in a chain. If a short circuit occurs, the circuit is overloaded. The breaker senses the overload, and trips to "Off." The action is like an old-style fuse blowing out. Breakers are rated by the maximum amperage draw. For example, a 15-amp breaker can only handle 15 amps of current. If a short circuit occurs, the amperage rises above 15 amps. Any amperage above 15 will immediately trip the breaker to the "Off" position, saving the rest of the circuit from overheating and causing a fire. (See note 1)
  
  

Industrial Controllers

• In an industrial automation system, the panel houses the main disconnect, breakers and programmable logic controllers, or PLCs (See reference 2 and note 1) PLCs are like computers. They accept inputs from machine sensors and vary electrical outputs to motors and robots accordingly. For example, a chocolate mold travels down a conveyor. When the mold hits a switch, a signal is sent to the PLC, through a wire. The PLC turns off the conveyor, through another control wire, and the mold stops. The mold is filled with chocolate by other machinery. When it is full, another signal is sent to the PLC, which turns the conveyor on again. Industrial electrical control panels have thousands of incoming and outgoing wires, and it is up to the electronics technician to read the blueprints and wire the panel in. (See note 1) Roger Hollingsworth of the University of North Carolina states that PLCs are compact and fit easily into a control panel, also called a control cabinet. (See reference 2)