VSDs: An energy-saving case

The two halves of the cases are made on two moulding machines. One of these machines is 15 years old while the other is only three years old. The only difference between the machines is that the newer machine already has a speed-controlled hydraulic pump. The company wanted to see if we could produce similar savings by retrofitting an electric VSD to the older machine.

The moulding machine has a 65-second cycle time. Around 30% of the cycle time is spent off load, during which the hydraulic system is not in operation but the pump motor is still running at maximum speed. Magma Moulding wanted to save the energy that was wasted here while avoiding affecting the cycle time.

ABB’s authorised value provider APDS conducted a week-long trial with an ABB drive to see how much energy could be saved. After consultation with Magma, it was agreed that installing a 55kW ABB general machinery drive would save £7800/year in energy costs, with a payback of just seven months. 

The VSD measures the torque in the motor to decide if the machine is on or off load and reduces the speed of the motor when off load. 

The moulding machine previously drew 40kW, but since fitting the drive, this has reduced to 23.5kW. As it runs for 4500h/year, the drive is saving 74,250kW/hrs annually.

Says Newbold: “We could gain even more electrical savings, but this would be at the expense of lengthening the cycle time.”

Magma Moulding intends to upgrade other machines with ABB drives from APDS.