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Product category: Stand-Alone Instruments
News Release from: Tektronix | Subject: Danfoss Drives
Edited by the Electronicstalk Editorial Team on 1 October 2001

Scopes boost productivity
for drives manufacturer

One of Europe's leading drives manufacturers is using Tektronix TDS3034 digital phosphor oscilloscopes as the heart of a novel 'test bench' concept

One of Europe's leading drives manufacturers is using Tektronix TDS3034 digital phosphor oscilloscopes (DPOs) from Danish distributor Teleinstrument as the heart of a novel 'test bench' concept designed to boost productivity in its development laboratories. Danfoss Drives, based at Grasten in Denmark, has integrated the Tektronix instruments along with standard power supplies and other measurement tools into special-purpose tables made by a German company, Telinot, to provide a standard modular platform for use throughout the development department.

The new test benches, of which there will eventually be 15, were developed as part of a complete restructuring of the Danfoss Drives engineering laboratories.

The philosophy behind this concept, which has been led by Kjeld Frederik Jacobsen, Purchaser of Development Support within the laboratories, is that all the 100-plus engineers within the company are regarded as 'customers' who can book time on each bench as and when they need to carry out tests.

The inclusion of standard rack-mount instruments and networked connections within each bench ensures that each member of the team knows that they will find a system that they can instantly use from the moment they start.

There are no problems caused by other staff members 'borrowing' measurement tools, and most of the probes, connecting leads and communications interfaces are already in place.

Moreover, the consistency of approach - which extends to training rigs and demonstration units within the company's marketing department - leads to a minimum learning curve and maximum productivity throughout the organisation.

Most of the work carried out by the Danfoss Drives engineers relates to power electronics - often involving high voltages and unpredictable interactions between power and signalling circuits.

In such a context, the performance and versatility of the Tektronix TDS 3034 has proved invaluable.

Its four-channel capability and colour display enable different waveforms to be examined, analysed and compared alongside each other, while its powerful computation capabilities allow instant calculation of power from current and voltage values - or more complex parameters such as the reverse recovery time of diodes within an IGBT module.

In some cases, the engineers are looking at very small signal variations in the presence of large signals - a 100mA pulse lasting only 20us on a 600A current waveform, for example.

Another problem is with intermittent glitches on the communications links between the electronic motion controllers and the high-power devices that control the drive itself.

In both these cases, the digital phosphor function of the TDS 3034, which emulates the persistence feature of an analogue storage oscilloscope, proves invaluable in helping to identify an infrequent event.

The oscilloscopes are typically linked with the device under test by current probes, but in many cases there are also connections to logic or communications signals at lower levels.

In these situations, the ability of the TDS 3034 to carry out automatic scaling, and display the widely differing signals side by side labelled with their appropriate units, proves invaluable.

Kjeld Jacobsen reckons that the standard test-bench configuration, which also includes high- and low-voltage power supplies, a multimeter and a function generator, meets 80% of the requirements for any team's experiments.

The remaining requirements are met by a range of special purpose units - dedicated current and high-voltage probes or instruments with exceptionally deep memory, for example - which are specified by the team using the bench beforehand and assembled by a dedicated member of staff before the tests start.

Kjeld Jacobsen selected the Tektronix oscilloscope for a number of reasons apart from its four channels and its colour display.

These included its compact size and ease of rack-mounting, its very attractive price (between four and eight times less than traditional oscilloscopes with the same performance), and the fact that he had dealt with Tektronix via TeleInstrument Denmark before and knew the reliability and customer support provided.

In addition, the instrument's built-in IEEE interface made it easy to integrate into their overall networking and control set-up.

Results are easily downloaded to PCs for archiving and analysis, and can be incorporated into spreadsheets or word-processor documents for inclusion in reports.

All the test benches are linked by fibre-optic cabling, and results from all the instruments can not only be shared throughout the development laboratories but can also be transmitted anywhere within Danfoss worldwide.

The Grasten plant is the main Danfoss Drives development and manufacturing centre for the company's VLT range of drives with ratings up to 45kW.

Larger drives are developed and manufactured at another plant in the United States, and the intention is that the test-bench concepts currently being developed at Grasten will also be implemented at the US plant.

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