Motor Drive Development – Still innovative after 20 years!!

Recently our Commercial Partner (Ms Patricia Elliott B.Eng) was kindly given an item by the company she used to work for (Nidec SR Drives Ltd.).  It was the last product she worked on before she left to set up Smart Power Solutions with our Technical Partner (Dr. Charlie Elliott). It is a high-power commercial vacuum cleaner unit used in larger homes and hotels in the US.

In order to keep size down and allow for long-life, a high-speed 2-phase Switched Reluctance Motor was used. To minimise input current whilst keeping cost low, a valley-fill power-factor improvement circuit was used. The control was implemented in a sub $1 microcontroller. As far as we are aware, nobody else has ever implemented such an innovative motor drive for this application since. When it was powered up in our lab, it worked after being sat in storage for almost 20 years!!

SPS is very well positioned to carry out motor drive development on all conceivable motor types. It has experience from low power 20W fans all the way up to 1MW mining applications. You won’t be surprised to hear that SPS is heavily involved in electrification of transport projects for both on and off-road use.

Innovative Motor Drive

EV SiC-based Inverter Project Update

SPS has just started testing the latest version of the highly challenging PCB it has designed for an automotive SiC-based EV inverter. The PCB not only implements all the required gate drive but integrates many other essential sensing and other auxiliary features to ensure electrical and functional safety. The space available for the PCB is very tight, the DC voltage high (up to 900V) and it has to press-fit to a power module where all the connection locationss are already set. The combined effect of this is that it has really challenged our most experienced PCB layout designer who has 25+ years experience.

The entire development of the PCB has been done in-house including the validation testing and manufacture of prototype PCBs. Given SPS’s senior staff have been working on xEV systems for well over 20 years, it is not surprising that our end customer has also asked us to assist with many other areas of their development. This includes advice on electrical / functional safety, EMC mitigation measures and thermal management. SPS has also carried out critical testing of the inverter system including full double pulse switch testing over the entire range of voltages, current and temperatures. This is an essential aspect of power electronics development that is unfortunately either skipped entirely or not done thoroughly by many other companies. This can result in an unacceptable amount of unknown risk in a product leading to reliability problems in the field. Most certainly not an option for an automtive product!! Please do contact us if our facilities and experience could be of use to your company.

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.

We are looking for more engineers to join our team

As a result of a significant increase in customer project activities we are current recruiting. Please see our dedicated page for more details Careers

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.