O’Brien Electrical Bundaberg can design, manufacture and install any type of motor starter required for your application from water pressure control, timed operation through to simple ON/OFF. We service the Wide Bay & Burnett regions including Bundaberg, Bargara, Hervey Bay, Maryborough and Childers.
Common starting methods available for electric motors are:
- Direct-on-line starters
- Star-delta starters
- Frequency drives
- Soft starters
The simplest and most common starting device is the direct-on-line starter where the equipment consists of a main contactor and a thermal or electronic overload relay.
The disadvantage of the direct-on-line method is very high starting current (6 to 10 times the rated motor currents) and high starting torque, causing:
- Slipping belts, heavy wear on bearings and gear boxes
- Damaged products in the process
- Water hammers in piping systems
A star-delta starting device consists normally of three contactors, an overload relay and a timer for setting the time in the star-position (starting position).
The starting current is about 30% of the direct-on-line starting device. The starting torque is about 25% of the direct-on-line starting torque.
The stress on an application is reduced compared to the direct-on-line starting method.
With a variable frequency drive the electrical frequency to the motor is modulated between typical 0-250 Hz.
- The rated motor torque is available at lower speed
- The starting current is low, ranging from 0.5 to 1 times the rated motor current
The frequency drive can also be used for soft stops.
With soft starters, thyristors are used to reduce starting voltage. With lower motor voltage, the starting current and starting moment can be very low compared to other methods.
Stress on the application can be close to minimum compared to other methods.
To learn more or to discuss your requirements, please contact us.