Electricity + Control November 2018

4

round up DRIVES + MOTORS + SWITCHGEAR

In the final of FOUR tutorials, Johan Basson of JB Switchgear, advises:

Motor control centres and how they work

circuit. Motor control centres have been around since the 1950s, when they were first used by the car manufacturing industry, which needed many electric motors. Today, they’re found in numerous commercial and industrial applications, specifical- ly where there are multiple, remotely controlled loads linked to a central control point. Modern MCCs offer a host of benefits, including: • Reduced downtime – standardised sections mean a simpler design, so operators require less operational training. Plug-in units can be easily swapped out for maintenance or replace- ment, and the inherent isolation of MCC units means they can safely be serviced individually, within legislated guidelines, without switching off adjacent units. • Quicker, cheaper installation – MCCs have their own factory-wired and tested units and pow- er buses, so field wiring and testing are mini- mised. • Flexibility – MCCs can be easily expanded by adding new units and sections. • Saves on space – much more compact than mounting individual devices. JB Switchgear is known in the industry for de- signing and manufacturing high quality switchgear solutions that meet the latest national and interna- tional safety and performance standards. We offer a comprehensive range of fixed, de-mountable and withdrawable motor control centres.

Think about what happens when you switch on your kettle in the morning. Apart from the encour- aging noises it makes, indicating that coffee is not far away, all kinds of clever things are going in in- side the kettle’s electrical circuitry. Every electric motor has a controller, and these controllers differ in complexity and number of fea- tures depending on the job they need to do. In the case of your kettle, the controller is the on/off switch, and you manually operate it so that your kettle can perform its very important task. Now imagine you had to make a thousand cups of coffee, and needed to switch on 500 kettles all at the same time. Not easy. In fact, pretty impos- sible. This is why motor control centres are such vital pieces of equipment, controlling everything through a centralised system. In its simplest application, a motor control cen- tre (MCC) is a panel that works as a motor start- er for several automated or semi-automated ma- chines. Comprising one or more enclosed sections with a common power bus, an MCC can include variable frequency drives, programmable con- trollers and metering. Essentially, they are a type of electrical 'filing cabinet,' with 'drawers' full of lighting contactors, combination starters and other electrical control and distribution products. Each section, or motor controller, of the cabinet has a built-in safety mechanism to protect the mo- tor. These can be solid-state overload protection re- lays, fuses or a circuit breaker, and there is usually a disconnecting switch as well to isolate the motor

Take Note!

1. Motorcontrolcentreswere first used by the car manu- facturing industry. 2. Today they are found in numerous commercial and industrial applications.

1

2

Every controller differs in complexity and number of features, depending on the job they need to do.

JB Switchgear Solutions is a leading manufac- turer of a comprehensive range of electrical switchgear systems. Enquiries: Email johanb@jbswitchgear.co.za

6 Electricity + Control

NOVEMBER 2018