The EAU is designed to be installed as a separate component between a servo system’s power supply and inverter, and recovers the energy that is generated when braking the servomotor. The energy, which is stored in a capacitor bank, can be fed back to the inverter when needed.
The EAU is aimed, in particular, at machines consuming 30–100kW that carry out repetitive movements – injection moulding machines or large presses, for example.
“The intelligent Energy Assist Unit controls the voltage in the servo controller automatically and independently directs the regenerative energy into the capacitor bank and from there back into the inverter,” explains Oliver Giertz, Mitsubishi’s product manager for servos, motion and robots in Europe. “So the amount of basic current required – and ultimately energy peaks too – are reduced significantly.
“As the EAU makes regenerative energy usable directly in the machine rather than just feeding it back into the electrical power supply system, the amount of basic current required will be reduced,” he adds. “As a result, energy peaks can also be reduced which represents another massive benefit for the user since he will then be able to adjust his existing contract with his electricity supplier.
“Subsequently, the contract will be determined based not only on the total annual energy consumption, but also on the energy peaks calculated,” says Giertz. “Ultimately, users will be able to save money as a result.”
A complete EAU energy recovery system includes a PLC, a Mitsubishi iQ motion controller, a converter, a drive and the capacitor bank. It can be operated via an HMI.
Mitsubishi is planning to market the EAU technology during 2015. It is not providing pricing details at this stage, but predicts that the typical return-on-investment time will be about a year.