Motor Starters – Control Panels – Automation and Monitoring Systems We design, build and test our own in-house control/monitoring panels, including HMI, SCADA, PLC programming, motor starters, inverter drives, temperature and pressure sensors. PLC and process controller programming / configuration, HMI (Human Machine Interface) touch screen /operator interface design and configuration. All types of motor starters; DOL, Star-Delta, and Variable Frequency Drive (VFD).
Some motors can be started using the star-delta method: the motor is first connected in ‘star’ configuration, which allows the motor to gather speed without drawing excessive current. Once the motor is up to speed (or a preset time is elapsed) it is then connected in the normal ‘delta’ configuration. This method can reduce the starting current demand by 30%, but is only suited to applications where the motor is starting without load.
DOL starting is simply switching the motor on in one operation, with a direct connection from the power source. It’s generally only used for smaller loads, as the starting current can be up to ten times the normal running current of the motor. A contactor is generally used to switch power, and often a thermal or electronic overload relay is provided for motor protection. Direct online starting is the simplest and cheapest method of motor starting, but consideration needs to be made for power supply limitations on starting current.
A variable speed drive (VSD), also known as a VFD or VVVF, is an electronic device which allows complete control of the motor speed including starting and stopping. It operates by changing the frequency of the power supplied to the motor. A VFD is extremely versatile and often used in process applications where a constant pressure or flow needs to be maintained. In addition, because the motor can be run at a slower speed and hence use less energy, use of a VFD can facilitate significant power savings.