VSDs cut energy consumption on quarry crusher

A quarry in the Midlands is benefiting from reduced running costs on a 160kW Metso cone crusher thanks to variable-speed drive (VSD) technology installed by Sentridge Control. Previously the crusher was equipped with a soft starter that was drawing up to five times the full load current. Not only was this an inefficient use of energy, but the crusher was causing problems with other equipment around the plant due to the voltage dip on start-up.

Glen Hickman of Sentridge states: "Softstarters do provide a smooth mechanical start but can draw high currents when activating, and they also produce less torque on start-up."

Following a free energy audit the Sentridge team reported their findings. The quarry management then authorised Sentridge to proceed with removing the soft starters and replacing them with VSDs.

Benefits of VSDs

Hickman comments: "Traditional slip-ring motors and starters were ideal, as they produced higher starting torque with lower currents - typically 1.5 to 1.8 times FLC - but they do not provide any variable speed control. They are becoming increasingly more difficult and costly to obtain and run than a conventional motor. The AC drive can overcome many of these problems, providing high torque at start, lower starting currents (typically 1 to 2 times FLC), smoother starting, variable speed control and, importantly, energy savings.

"Energy savings are achieved by precisely matching the motor load and accurately controlling the output voltage of the drive to the required levels. This can provide off-load energy savings of up to 20 per cent. In addition, product quality is better controlled, with more information on the crusher loading, torque and power being closely monitored by the drive."

Improvements were achieved as follows:

• Energy savings
• Reduced noise
• Eliminated maintenance associated with soft starters
• Reduced stresses in power transmission components
• Enhanced reliability

For more information about free energy audits and using VSDs to save energy, call +44 (0)24 76 553303 or email sales@sentridge.com.