Electricity + Control July 2017

DRIVES, MOTORS + SWITCHGEAR

abbreviations

MCC – Motor Control Centre VFD – Variable Frequency Drive

Motor Control Centres How They Work Johan Basson, JB Switchgear

Motor Control Centres (MCCs) have been around since the 1950s when they were first used by the car manufacturing industry, which needed many electric motors.

T hink about what happens when you switch on your kettle in the morning. Apart from the encouraging noises it makes, indicating that coffee is not far away, all kinds of clever things are going on inside 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 MCCs are such vital pieces of equipment, controlling everything through a cen- tralised system. In its simplest application, an MCC is a panel that works as a motor starter for several automat- ed or semi-automated machines. Comprising one or more enclosed sections with a common power bus, an MCC can include variable frequency drives, programmable controllers and metering. Essen- tially, they are a type of electrical ‘filing cabinet,’ with ‘drawers’ full of lighting contactors, combina- tion starters and other electrical control and distri-

bution products. Each section, or motor controller, of the cabinet has a built-in safety mechanism to protect the motor. These can be solid-state over- load protection relays, fuses or a circuit breaker, and there is usually a disconnecting switch as well to isolate the motor circuit. While they were first used in car manufactur- ing, today MCCs are found in numerous commer- cial and industrial applications, specifically where there are multiple, remotely controlled loads linked to a central control point. Conclusion 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 re- placement, and the inherent isolation of MCC units means they can safely be serviced indi- vidually, within legislated guidelines, without switching off adjacent units • Quicker, cheaper installation: MCCs have their own factory-wired and tested units and power buses, so field wiring and testing are minimised • Flexibility: MCCs can be easily expanded by adding new units and sections • Space saving: 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. The company offers a comprehensive range of fixed, de-mountable and withdrawable MCCs, so talk to us about how we can help you get the solu- tions you need.

Take Note!

An MCC is a panel that works as a motor starter for several automated or semi-automated ma- chines. An MCC can include Var- iable Frequency Drives, programmable control- lers and metering. MCCs control everything through a centralised system.

1

2

3

Essentially, an MCC is a type of filing cabinet.

<>

Johan Basson is the Managing Director of JB Switchgear.

+27 (0) 11 027 5804 / +27 (0) 82 852 401 info@jbswitchgear.co.za www.jbswitchgear.co.za

14 Electricity + Control

JULY 2017