greenpowerZONE Products for the week of June 12, 2006
Texas Instruments Says....
TI Controllers Teams With Tier Electronics to Boost White Good Efficiency By Up To 30%
Three-phase asynchronous motors incorporate FOC for quieter, faster and more efficient white goods at lower system costs
As fuel prices and electric power rates continue to climb, the incentives for energy savings have never been greater. Embracing this opportunity for conservation, Tier Electronics LLC and Texas Instruments Incorporated announced that TI's digital signal processing- (DSP) based TMS320C2000 controllers are the key component in Tier's motor control system for washing machines and other white goods. System designers using Tier's Mini Universal Power Converter (UPC) can harness the processing power and efficiency of TI's C2000 controller that, when combined with Intelligent Power Modules (IPM) and pressure-stamped heat sinks, can reduce costs by up to 25% by halving component counts and can deliver up to 30% better efficiency compared to conventional microcontroller (MCU) or discrete-based designs. The reduction in parts count will also improve MTBF (mean time between failure) ratings.
Efficient Design Delivers Impressive Results
Many of today's white goods use conventional single phase motors that require simple control algorithms and hardware, but are noisy, bulky and waste energy. To avoid this problem, designers have to maximize efficiency, making sure that motors are used to the fullest extent in order to minimize the amount of power wasted. The UPC design integrates TI's C2000 controller, enabling use of a multi-phase alternating current (AC) motor that can be controlled with an adaptive-based field oriented control (AFOC). Multi-phase AC motors controlled with an adaptive algorithm are smaller, run more quietly and provide precise speed and torque control based on a machine's load to avoid wasting energy. The AFOC scheme strives to maintain an angle between the rotor flux and the stator flux that is optimized to improve motor efficiencies, while actively controlling the torque, therefore significantly improving overall performance. The AFOC vector control reduces the voltage and current peaks and valleys associated with scalar and traditional FOC control, which also produces quieter appliances.
Additionally, digital signal controllers provide improved pulse width modulation (PWM) control compared to conventional control systems, keeping a motor's total harmonic distortion (THD) at a minimum over a wide operating range. This also leads to lower operating temperatures, higher efficiency, better power factor ratings and lower materials costs, especially in regards to the amount of copper required for the motor. The digital signal controller's ability to produce cleaner waveforms translates into the ability to use a motor that is smaller and does not need external sensors.
In addition to utilizing the powerful computing capabilities of TI's C2000 controllers, Tier employed innovative technologies to achieve its advanced motor controller design. Intelligent Power Module (IPM) technology reduces Bill of Material (BOM) and manufacturing costs with its high level of integration of components including insulated gate bipolar transistors (IGBTs) and free wheel diodes. Advanced built-in protection is another feature of the IPM which improves reliability by up to 30%. Pressure-stamped heat sinks round out the motor control system's triple play. They use a procedure of cold extruding solid aluminum pieces into precise shapes in a single process. They are less costly to manufacture and deliver superior heat dissipation compared to conventional heat sinks.
DSP Power and Performance + MCU Peripherals = Success
"We determined early on that TI's C2000 controllers were the only product that met all of our requirements. These devices provided the number-crunching capability necessary for AFOC control along with enough headroom to integrate advanced features like power factor correction, motion profiling and spread spectrum PWM generation," said Jeff Reichard, CEO, Tier Electronics LLC. "Having a motor control platform that is reprogrammable in software allowed for easy tweaking or adjustment of systems to increase efficiency or enable system re-use with different motor types."
TI's 16-bit TMS320F24x fixed-point DSP-based controller provides up to 40 MIPS of performance and features an integrated single-cycle multiplier, seven pulse width modulation (PWM) variable frequency and dead-time ports, five or more ultra-rapid 10-bit analog to digital converters (ADCs), an impulse capture circuit with a 16-bit timer and asynchronous serial communication. Integrated Flash memory allows re-programmability during the development phase and in the field, which satisfies low cost constraints and speeds time to market. A low cost, pin compatible ROM version designed specifically for appliance applications is also available.
EN-Genius Says...
It's very exciting to see so TI and so many other electronics companies discovering the virtues of green power design and finally bringing decade-old concepts to commercial reality. Actually, TI has been in the energy-efficient white goods for some time, but concentrated its efforts in Europe and Asia and I have not been able to get any details on the products they have been pushing there. This situation appears to have changed with the very appropriate pairing of TI's DSP and controller know-how with Tier's expertise in high-power electronics to produce a nice reference that takes square aim at the North American market for higher-end washing machines and any other kind of appliance running a 3-phase motor.
Of course they're entering a lively market, already occupied by very capable products from the likes of ADI, International Rectifier (see April 2006 review) and STMicroelectronics, but given the volume of washers, dryers, and dishwashers we purchase every year, there's probably room for at least one more competitor. TI's solution may well appeal to the many manufacturers whose design teams are still more familiar with ac motor technology than the permanent magnet synchronous motors (PMSMs) that International Rectifier's system is designed to drive.
In fact, the TI controller can drive both switched-reluctance induction-type motors highlighted in the release above and the permanent magnet type motors that International Rectifier's controllers are designed for. Thanks to its flexibility, TI's controller could allow designers working in the relatively conservative North American white goods market to improve the energy efficiency of their current induction motor-driven products by simply changing the control circuits. This would also build in the option to move to a PM motor in the future.
Some arguments have been made that PM-based motors are inherently a bit more efficient than inductive motors (mostly because of the losses incurred in energizing the rotor coil). But even if this is true the TI solution should come very close to a PM in overall efficiency thanks to the precise waveshaping of the phase inputs afforded by the C2000 DSP. I'd expect it to be able to do the same great job with shaping motor drive waveforms that it did with producing pitch-perfect phase-matched ac for grid-tied solar-electric inverters that won our greenpowerZONE Product of the Year 2005.
A closer look at TI's motor controller reveals that it is not as much of an application-specific turnkey design as IR's offerings, but more of a general-purpose kit that can be adapted to a variety of requirements. The unit is basically a 3-phase bridge plus a rectifier which gives a designer lots of flexibility. For smaller 120-V ac designs that employ wall plug power, the DSP-based system can actually take the single phase, apply PF correction and output 3 phases with a single 3-phase bridge. Higher-power designs can employ a more conventional 3-phase in/3-phase out arrangement. This can be accomplished via either a dual 3-phase bridge for a sinusoidal input current and a 3-phase motor controller output with 4-quadrant capability, or using a conventional diode bridge input.
But regardless of what motor you're driving, having a programmable DSP at the heart of the controller enables you to precisely control stator/rotor flux angles, THD and power factor correction, for highest efficiency. This near-infinite control over the waveforms also has other advantages, such as being able to get rid of the high-pitched noises often associated with conventional PWM controllers using a technique TI calls "spread spectrum PWM generation." By using spread spectrum techniques to modulate a lower base PWM frequency, the controller can change the single piercing tone of a conventional PWM controller to something more like a hiss or wind rush.
The DSP's smarts can also be used to eliminate the cost of Hall-effect sensors normally used to sense speed and rotor position. Depending on the motor and speed range, the motor speed can be calculated using current and voltage sensors. TI says its controller has been used for BLDC sensorless motors up to 90,000 rpm.
Depending on the software and I/O it's configured with, the unit can work with a standard motor and gearbox assembly found on older designs or with a newer design multi-pole direct drive motor. Besides eliminating the noisy, expensive transmission assembly, the combination of programmable control and direct-drive gives consumers several plusses including sophisticated agitation cycles that are gentler on clothes and more effective at getting the dirt out and ultra-quiet operation. On the green side of the equation, the wicked-fast spin cycles it delivers enable it to extract more water from the clothes to save dry time and lots of energy.
This ability to precisely control the motor opens up some other fascinating opportunities for adding innovative functions, such as being able to detect the position of a lump of clothes causing an out-of-balance condition in a washer drum before it goes critical and applying the appropriate acceleration or deceleration to re-distribute it more evenly. It might even enable an "all-in-one" laundry unit which washes and dries your clothes in the same drum. Unfortunately, TI was unable to comment on whether any of its customers was actively pursuing such a design.
Manufacturers will also appreciate the TI solution because it can help deliver more features and functionality while keeping BOMN costs under control. Besides eliminating the sensors, as described above, the DSP has enough surplus processing power that it can absorb the control, communication, and user interface tasks normally handled by a second controller chip. TI's upper driver power supplies eliminate the need for costly isolation transformers (typically found in bootstrap diode configurations). TI also claims that by using a single controller board for over 16 models and 3 different motor types, the design enjoys huge economies of scale.
On the downside, it would appear that TI's partner for the high-power final drive elements is not quite as mature as IR's. Both company's power modules use efficient, sturdy IGBTs as their core technology, but as my colleague Paul McGoldrick observed, Tier's power modules appear to be less mature and integrated compared to IRF's current offerings. This is not surprising since Tier is a relative newcomer (founded in 2003 making mostly custom products) so they will have to scramble up a steep learning curve to deal with the logistics of such a cost-sensitive high-volume market, or develop relationships with another company that's already up to speed. TI says that for very high volumes they can actually set up the OEM so that they can purchase the unit directly from a contract manufacturer to help keep the costs in line with the tight margins associated with consumer white goods. They are also open to selling design rights so a company can manufacture their own modules.
Pricing is a little tricky to pin down since this is not a one-size-fits-all sort of system which is custom-tailored to each application. TI does say that a combined DSP/power module (they don't offer the control PCB as a separate item ) capable of driving a 1 hp induction motor costs around $15 in very high volumes. They also say that they are in the middle of re-costing the line using the newest DIP and Mini DIP modules, something I expect will make them even more competitive. For more pricing and availability information for Tier's product go here and click on "RFQ" for the Mini UPC on the "Products" page. For more information on the full line of C2000 digital signal controllers, see http://www.ti.com/c2000.
Data Sheet TMS320LF2401A
Data Sheet TMS320LF2402A
Tier IGBT Modules
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