Power Control Panel
An electrical control panel is a combination of electrical devices which use electrical power to control the various mechanical functions of industrial equipment or machinery. An electrical control panel includes two main categories: panel structure and electrical components.
PANEL STRUCTURE OF ELECTRICAL CONTROL PANELS
The structure of an electrical control panel is a combination of an enclosure and a back panel, similar to a breaker box.
Enclosures
The enclosure is a metal box which varies in size and is typically made of aluminum or stainless steel. The number of doors (usually one or two) needed on the enclosure determines its size in most industrial applications. The enclosure will come with a UL safety rating (508A is typical) an IP rating, and/or a NEMA classification. These listings help users determine properties such as:
- Indoor/outdoor use
- Waterproof/water resistance
- Dust/solid contaminants proofing
- Hazardous conditions rating
- Explosion-proof rating
These various classifications should be printed on a metal plate and attached to the enclosure for easy identification and reference.
Back Panels
A back panel is a metal sheet mounted inside the enclosure that provides structural support for DIN rail mounting and wiring ducts. DIN metal rails feature standardized dimensions and provide a mounting structure for electrical devices. Assembly Wiring ducts provide for the routing and organization of wires while also assisting in the control of electrical noise between devices inside the box.
ELECTRICAL CONTROL PANEL ELECTRICAL COMPONENTS
Eight types of electrical components exist within an used electrical panel enclosure which define and organize the several different functions carried out by the panel. These components include:
- Main circuit breaker. This is like the disconnect of the main electrical panel leading into a home or office. Miniature circuit breakers handle between 120V–480V in most industrial applications which established control over circuit components.
- Surge arresters. This component prevents lightning strikes or utility power surges from damaging the electrical components inside the panel due to overvoltage.
- Transformers. Depending on the incoming voltage, transformers may reduce voltage to 120V for various components or step down voltage to 24V in instances where incoming power is 120V.
- Terminal blocks. These blocks help to organize and distribute the array of wires coming from various sources to different electrical devices.
- Programmable Logic Controller (PLC). This is essentially a CPU contained inside the control panel. This unit is the brains of the control panel, providing monitoring and control of the various mechanical processes. In will include various inputs and outputs to and from mechanized functions of the production equipment.
- Relays and contactors. These on/off switches control mechanized functions based on commands from the PLC. Smaller relays control functions like lights and fans. Larger relays, called contacts, control more advanced functions like motor controllers.
- Network switches. The communication hub of the control panel, network switches facilitate communication between the PLC and the various network compatible devices on the production line.
- Human Machine Interface (HMI). These components allow an operator to monitor or control certain functions of the machinery. Common HMIs include video monitors, joysticks, buttons, switches, and keyboards.