AC and DC drives have the same `look and feel`

Eurotherm has developed two new families of drives - one AC, the other DC - that look identical and use the same programming techniques, communications and set-up procedures.

The company asserts that this "unique" approach will save time and make life easier for users who will only need to become familiar with one programming method and interface. Both families of drives are programmed using function blocks that define functions such as inputs, outputs or PID controls.

For simple applications, these blocks are preconfigured, allowing the drives to provide basic speed control straight from the box. For more complex applications, the blocks can be interconnected to create an exact control scheme. Both types of drive also accommodate up to three optional plug-in "technology boxes" offering functions such as operator interfaces, encoder feedback and serial communications - including Profibus, DeviceNet and fibre optic links.

The drives are the culmination of three years` work by Eurotherm engineers on both sides of the Atlantic, says Mark Hartley, the company`s UK sales manager. More than 100 person-years of development work have gone in to the new ranges, he adds. The DC drives represent "a radically new approach to DC control", according to Eurotherm.

They are available complete with components such as AC line contactors, AC and DC fuses, auxiliary control transformers and fans that are usually specified separately. Hartley argues that this approach will save users time and money as well as cutting the panel space required for a drive. "No one else does anything like this," he adds.

The DC range, called the 590+, comes in packages from 35-2,700A, in both regenerative and non-regenerative configurations, with options for six-, 12 or 24-pulse control. It will supersede the existing 590 series which Hartley claims is the UK`s best-selling DC drive.

The AC family, dubbed the 690+, can be configured for basic volts/frequency control, sensorless vector or closed-loop vector control. Initially it will cover ratings up to 55kW and will extended soon to 355kW. The AC drives incorporate an advanced current control loop that measures and controls current in both the sensorless and closed-loop vector modes, rather than simply limiting the peak value as happens in some rival products. Eurotherrn claims that this improves performance a low speeds, and provides trip-free acceleration and deceleration.

"You can whack the drive harder for current demand," says Hartley. It allows bandwidths up to 700Hz for dynamic applications such as web processing and phase control. The new drives families will make their debuts at next month`s Drives & Controls show. The DC versions will be available immediately, with the AC models following soon after, according to Hartley.