A unified drive-how and why?

Some manufacturers offer a range of similar variable speed drives to cover a range of applications and motor types so that their customers do not have to be familiar with several different products. The set-up and control of drives is never the same throughout a range and the user must keep several sets of different spares. A unified drive which incorporates the necessary power and control elements for more than one type of motor would help to address the problem. A majority of AC motor applications from 0.75 kW to 1 MW can be covered by the following: open loop AC motor drive (for induction, reluctance or permanent magnet motors); sensorless vector AC induction motor drive; closed loop vector AC induction motor drive; and closed loop permanent magnet synchronous (servo) motor drive. These are all normally based on a PWM voltage source inverter and controlled by microprocessor based hardware. This has allowed all four to be combined to form the Unidrive in which the type of drive is selected simply by changing a software parameter, and which can operate in each of the four configurations without any additional hardware modules. It is not possible to use exactly the same control algorithm in each case, but as described in this paper there can be a high degree of commonality between drive types. This is an enormous benefit in the design process as it reduces the effort required to produce the drive software. It also benefits the user because the drive parameter set differs little between each drive type