Extremely compact multidrives, such as the ACS800, offers an array of benefits to integrators, OEMs, panel builders, and end users who are optimizing energy usage through precise control of motors. Since drives are available both in multidrive and single drive configurations, it is useful to define the difference and profiles the benefits that the next generation of multidrives now provides to users.
Adjustable speed drives are used in any application in which there is mechanical equipment powered by motors; the drives provide extremely precise electrical motor control, so that motor speeds can be ramped up and down, and maintained, at speeds required. Doing so utilizes only the energy required, rather than having a motor run at constant (fixed) speed and utilizing an excess of energy. Since motors consume a majority of the energy produced, the control of motors, based on demands of loads, increases in importance, as energy supplies become ever more strained. Additionally, end users of motors can realize 25-70 percent energy savings via use of motor controllers. (Despite these benefits, the majority of motors continue to be operated without drives.) Single industrial drives are highly flexible AC units that can be customized to meet the precise needs of a single-motor application. These units convert AC power to DC, and then invert the DC back to an AC output to a motor. These drives cover a wide, full range of powers and voltages. Single industrial drives also feature a wide range of built-in options as standard equipment. They can be installed for most applications right out of the box; and they also can be ordered and manufactured as a customized unit for a particular application. A multidrive is built from industrial drive modules that are connected to a common DC bus bar. The common bus bar is used to supply the drive modules with DC power, and each module then inverts the DC to AC and powers an individual motor. The DC power is derived from a single supply unit (rectifier) that is built into the front end of the same multidrive configuration. This construction simplifies the total installation and results in several benefits: savings in cabling; reduced line currents and simpler braking arrangements; energy distribution over the common DC bus bar, which can be used for motor-to-motor braking without the need for a braking chopper or a regenerative supply unit; reduced component counts; increased reliability; and space savings; and there is no need for a separate motor control center (MCC). But where can multidrives be used?In general terms, multidrives can be used whenever several drives/motors form part of a single or integrated mechanical process. The common supply of the multidrive enables the implementation of overall safety and control functions, and permits the close coordination of individual drive motors. Modular configuration of multidrives provides control of multiple motors across a 1-7,000 hp power range, from 380-600 (690) VAC. A single rectifier unit can be combined with a host of inverter units that are connected in parallel, to provide output current required by any given application. Additional benefits include:
• Encoder-Less Motor Operation: Many applications can be run without encoder feedback.
• Flexibility: Only four types of diode rectifiers are used to invert AC three-phase input power to the common DC bus bar across the entire ACS800 power range (200-4600 hp).
• Compact Design: Improvements in technology and power components have reduced the total footprint of multidrives by up to 50 percent.
• Adaptive Programming: This program extends the freely programmable I/O and extensive parameter selections built into multidrives and accessed via the start-up assistant.
• Reduced Installation Costs: Both the rectifiers and the inverters are rolled in on their wheels and seated into the connectors.
• Redundancy: Common spare parts and the ability to keep running at reduced load, if module is disabled.
Ari Hedemaki works as product line Manager for ACS800 industrial drives in ABB’s Low Voltage Drives office. He is responsible for high horse power single drives, cabinet built drives, and multidrives. He has worked for ABB LV Drives and MV Drives since 1994.