A control panel is made up of many electrical components, designed to distribute the power to several avenues. Below we cover the common items although some systems contain many others.
In the context of control panels & LV switchboards the busbar is the main conduit through which electrical power is transmitted from device to device. Usually made of bare copper, but also comes in tinned copper, coated (heat shrink), aluminium & Cuponal®. Each of these has their own advantages and disadvantages when it comes to weight and current carrying capacity.
Busbars have an advantage over traditional cabling, with greater surface area for cooling & the ability for 90° changes of direction, no bending radius to be considered in the routing.
An ACB uses pressurised air to stop the electrical current flow. Other alternative circuit breakers include Oil & Vacuum style Circuit Breakers.
When the contacts separate an arc forms, as the electric current tries to maintain its flow, this arc damages components. Think of it as a lightning strike, so the pressurised air extinguishes it as fast as possible to prolong the life of the equipment. Just like blowing out a candle.
This arcing is why all electrical contact equipment should be subject to periodical maintenance checks for wear & tear.
The ACB is the main incoming protection device, that protects everything downstream from excessive currents & faults, generally larger in size and rating (up to 6300 amps).
An ACB is the main electrical contact that must connect live (MCCBs etc are downstream and can be turned on and off when the power is dead).
A molded case circuit breaker (MCCB) is a type of electrical protection device that is used to protect the electrical circuit from excessive current, which can cause overload or short circuit. With a current rating of up to 2500A, MCCBs can be used for a wide range of voltages and frequencies with adjustable trip settings.
These are generally on the outgoing circuits from the panel, feeding other panels, larger systems, UPS, etc.
These generally come with a Thermal Trip and Electromagnetic Trip (the thermal is a bimetallic contact that expands at differing rates and eventually separates the 2 contacts, the electronic trip uses a magnetic solenoid, when the short circuit current gets too large it disconnects the trip bar.)
The magnetic field then forces the arc into the plates and extinguishes it.
These are essentially a mini version of an MCCB, but usually restricted up to approximately 100amps.
Types of Miniature Circuit Breaker
MCB trip curve decides the type of MCB that must be used for different appliances or devices. There are different types of MCBs, they are: B C D K & Z.
These just have different reaction times & sensitivities so therefore are suitable for different applications / loads.
When the current overflow occurs through MCB – Miniature Circuit Breaker, the bimetallic strip (13) gets heated and deflects by bending. The deflection of the bi-metallic strip releases a latch (1). The latch causes the MCB to turn off by stopping the current flow in the circuit. This process helps safeguard the appliances or devices from the hazards of overload or overcurrent. To restart the current flow, MCB must be turned ON manually.
Advantages of an MCB, they are small (obviously) relatively cheap to replace and easy to reset.
B Type MCB trips off the circuit when the current exceeds 3-5 times the current flow and finds its application in cable protection.
C Type MCB trips off the circuit when the current exceeds 5-10 times the actual current flow and finds its application in domestic as well as commercial appliances like transformers, fluorescent lighting circuits, and IT equipment like personal computers, servers, and printers.
D Type MCB trips off the circuit when the current exceeds 10-20 times the current flow and offers high resistance. It finds its application in motors.
K Type MCB can withstand up to 8-12 times the current flow and finds its application in heavy-duty load devices like compressors, winding motors, and X-ray machines.
Z Type MCB trips off the circuit when the current exceeds 2-3 times the actual current rating. Z type MCB – Miniature Circuit Breaker is highly sensitive to the short circuit, and hence we can find its application in the manufacturing of semiconductors.
There are many types of terminal block, the most common in control panels is the Din Rail mounted style. A terminal block is an insulated outer frame that houses metallic terminals that connect 2 or more wires together. They often have an area for identification of the cable ID as well.
They can be spring loaded or screw type and are designed to grip the ferrule / cable end and perform a secure electrical connection.