More kit for the lab

We have recently made one of our most expensive equipment purchases in order to expand our validation testing capabilities and improve our efficiency. This is a bidirectional (source or sink) power supply that is capable of both AC and DC operation. This 30kVA / 800VDC / 510 V L-L unit also allows single or 3 phase outputs to be generated with huge flexibility in terms of both steady-state and transient waveforms. We have been looking to purchase such a unit for a while and our Technical Partner Dr. Charlie Elliott spent a lot of time researching what was available on the market. In the end we are delighted to say that an independent Spanish company called Cinergia were selected. The unit has clearly been designed by practising power electronics engineers who know exactly what is required on the user interface, communications (Ethernet and CAN) and advanced DSP based controls. The unit has already been used for testing a high efficiency motor drive system. It will also be used for production testing some high energy storage “ultra capacitor” systems in the near future and no doubt plenty of other projects moving forward.

PLECS – We just added another seat

We have been big fans of Plexim’s PLECS simulation tool for power electronics for quite some time. We use it across most of our projects for component sizing, controls development and looking at system level behaviour. Our technical partner first came across it many years ago when it was still a free netlist-based basic tool provided by a university. Since then it has been fully commercialised and has come on in leaps and bounds. We have just added another seat of PLECS as we are so busy. This time we have decided to go for the standalone version which doesn’t require Matlab or Simulink. This version also has some additional features which we will no doubt find useful.

New Isolated Scope for the Lab

We are great believers in investing in our lab equipment to make us efficient but always have to keep an eye on costs. Being a modest size outfit ourselves, we are also keen on supporting the small guys out there. When one of our scopes recently failed and it was uneconomic to repair, we therefore had a good look round for what was available from both the big T&M outfits and the smaller independent ones. Not only did we want 4 analogue channels with decent memory depth but also preferably higher resolution than a standard scope and digital logic inputs. At the same time we had been finding that making power switching measurements at high DC voltages was becoming increasingly difficult especially with more modern (faster) transistor technologies. Thus we also wanted something with very low coupling capacitance to earth and preferably isolated inputs, We were amazed to find a unit which met all our requirements by buying the PC based CS448 from NZ based based Cleverscope. Our technical partner was particularly impressed with the care and thought that has gone into the all important front-end of the product and their money back guarantee was the final clincher. The first job the unit was used for was to look at detailed gate drive waveforms on a high power SiC based inverter system. The results were very impressive indeed with very clean waveforms showing the expected “miller effect” waveforms that were previously covered in noise. They even had some custom x200 probes made so we could do power switching waveform measurements at higher DC bus voltages!! No we don’t have any vested interest in those clever chaps in NZ but when you see something you like you should let others know…

PCB Design Software Upgrade

We have recently made a significant investment to upgrade our PCB Layout software (Mentor PADS) to the latest version. This introduces a whole range of new features including significantly enhancing 3D mechanical integration and allowing more complex rules to be defined for meeting electrical safety spacings. This should improve our efficiency in carrying out the challenging designs we have to do which regularly require complex mechanical interaction and also reduces risk as accurate 3D (step) files can be both imported and exported easily. At the same time we have taken the opportunity to improve our parts library to provide better uniformity across projects.

Two New Members of Staff

We are delighted to report that two new members of staff have joined SPS as a result of our recent recruitment drive. Both of them have a keen interest and relevant experience in power electronics applications. This is great news for the company as we are so busy. We are still interested in anybody else who would be interested in working with us. Please contact us via the form.

Vapour Phase Reflow Oven Commissioned

Zen Production Ltd. have now fully commissioned and installed our vapour phase SMD reflow oven. Since first trialling such an oven in October 2015, Zen kindly loaned SPS their demonstration oven until the model we had selected was available. We have now swapped over to using this and are looking forward to the same high quality results.

SPS Utilises Rapid Prototyping Controls Again

SPS is making great use of its general purpose power conversion controls platform again. This was initially developed as part of a Technology Strategy Board (now Innovate UK) part-funded project in 2009 – with TSB funding this meant the IP was retained by SPS. The controls platform was developed to allow rapid prototyping of systems for customers in the initial proof of concept phase. For the TSB project it allowed SPS to implement a very specific motor control hybrid vehicle requirement. The platform has been invaluable on numerous projects allowing us to use existing building blocks to rapidly prove out initial concepts to customers with low risk and cost. Once the concept is proven, a lower cost targeted implementation can then be developed. The current use is on a 50kW compact static power conversion application.

We are already in the process of revamping this controls platform to take advantage of the latest generation of microcontrollers and to also incorporate additional robustness and flexibility so that it can be used in lower volume niche applications for the manufacturing side of the business. We hope to be able to report on that progress in Q2 16 and publish a full specification.

SPS Trials Second SMD Reflow Oven

SPS is trialling an Asscon VP450 small batch vapour phase oven kindly provided by Zen Production Equipment Ltd. (www.zpel.co.uk). We were very impressed by the professional and open approach of Zen both in terms of sales and on-site commissioning support. The very first PCB trialled with the unit was a complex design incorporating significant copper floods with larger SMD components as well as other areas with just signal electronics. Our experienced production technician was very impressed with the excellent quality solder joints that were immediately evident and the simple operation of the machine. As a result of this initial trial and other subsequent successful uses of the machine, the decision was made to go ahead and purchase.

Review of in-house SMD Soldering

Having our own internal capability for high quality assembly of SMD PCBs for prototyping and small manufacturing batch runs has always been essential to meet customer lead times. Without a large multi-zone heater reflow oven and the possibility of tweaking parameters to optimise production yield, this is not a straightforward task. This has been compounded by the move to lead-free soldering and the same PCB having a large range of size and weight of components and tracking / flooding. Historically a modest size convection reflow oven has been used by SPS but it was apparent that a higher performance oven would be required for future use. An internal review of different reflow technologies was carried out by our production department and advice sought from various suppliers. After poor results from trialling a popular oven specifically designed for low volume / batch work, advice was sought from Electronics Yorkshire. They recommended using vapour phase technology which SPS was familiar with as a technology as it has been used for many years for soldering copper base plates to the underside of the DBC in isolated power modules.