An AC drive that combines accurate speed control and Direct Torque Control (DTC) with line braking for regenerative applications such as cranes, centrifuges and winding machines between 11 kW and 55 kW, is launched by ABB Industry Oy, Finland.

The ACS 611 incorporates two inverters in one frame. An active inverter replaces the usual diode rectifier on the incoming AC power reducing harmonics and ensuring the delivery of a virtually sinusoidal supply.
This extra inverter also enables full four quadrant operation and a two way flow of energy, which means that the drive can divert excess energy from a braking motor back into the electrical system when it is not needed by the motor. This means that the ACS 611 can achieve large energy savings in applications where energy from a braking motor is transferred back into the electrical network for use by other plant applications instead of 'wasted'.
Adaptation of ABB's proprietary DTC technology allows the drive to switch between maximum motoring to maximum generating power in under five milliseconds allowing the drive to adapt to very dynamic changes in motor load.
In addition, should there be a drop in the line voltage, the drive will quickly adapt to maintain a stable DC voltage for excellent ride-through performance.
By re-directing unused electrical energy, the ACS 611 also eliminates the installation of large braking resistors, which take up valuable floor space and
dump considerable amounts of waste heat energy into the atmosphere. This in turn reduces the drives' ventilation and cooling requirements and further cuts plant costs. The drive also avoids the complicated set up and tuning requirements of mains-operated thyristor feedback units.
"When talking about the development of a new switching technology or advanced motor control platforms like DTC it is sometimes easy to loose sight of the primary function of a drive, that is, to save energy." says Ian Rennie, Vice President of ABB's global drives operation. "The ACS 611 regenerative drive emphasises this primary function and offers potentially huge savings in conjunction with the advanced technological features and life-long support that the market expects from ABB's drives."
By developing the "adaptive motor model" theorem behind DTC, the ACS 611 drive is capable of tracking the torque and magnetic flux by measurement of the intermediate circuit voltage and two-phase currents alone.
The ACS 611 is available in six different power ratings between 11 kW and 55 kW all using the same frame size. The drive offers software alternatives for standard and system installations and an extensive collection of application macros for cranes and motion control.
The drive features a variety of control connection possibilities. These include three programmable differential analogue inputs and six digital as well as five programmable outputs, two analogue and three digital. The ACS 611 also features optional I/O modules and fieldbus adapters.

Photo caption:
The ACS 611 can achieve large energy savings in applications where energy from a braking motor is transferred back into the electrical network.

For further information contact:
ABB Industry Oy
Roelof Timmer, Marketing Director
P.O. Box 184
FIN-00381 Helsinki
Tel. +358 (0)10 222 000
Fax. +358 (0)10 222 2681
http://www.abb.com/automation
Email: roelof.timmer@fidri.mail.abb.com