 greenpowerZONE Products for the week of April 3, 2006
International Rectifier Says....
IR's PM Synchronous Motor Controller Solution Cuts BOM Cost, Enables 95% Efficiency In Air Conditioning
International Rectifier has introduced a motor control platform for air conditioning applications that enables 95 percent efficiency, quieter operation and mechanical simplicity. IR's iMOTION integrated power design platform enables energy-saving, variable-speed sinusoidal current control without the need for position sensors for smooth torque output and lower acoustic noise in motors.
The International Rectifier power design platform is an optimized system architecture that combines IR's proprietary high voltage integrated circuit (HVIC) technology with analog, digital and power building blocks, along with digital control algorithms, for sensor-less motor control applications using dc link phase current sensing.
"IR's iMOTION platform is one of the first of its kind to address energy-saving motion control from a systems level. The platform provides everything a designer needs to deploy the benefits of variable speed motion control in air conditioners. This means systems that were once about 60 percent efficient will become better than 90 percent efficient. This is particularly important in places like China where air conditioner usage has grown about four fold -- from 8 to 31 units per hundred households -- in the space of five years," said David Tam, vice president of International Rectifier's Energy Saving Products Segment.
The air conditioning platform features a proprietary algorithm for interior permanent magnet synchronous motors (IPMSM) in the compressor as well as the fan, and includes power factor correction (PFC). This, combined with IR's application-specific HVICs and discrete trench IGBTs, achieves 95 percent converter efficiency.
Digital Section
iMOTION's digital block consists of the IRMCF3xx family of digital control ICs. These ICs include IR's patented Motion Control Engine (MCE) that implements the complex sensor-less PMSM algorithm in hardware, thus eliminating software coding from the development process. The IRMCF3xx also features an embedded analog signal engine (ASE) that integrates all signal conditioning and conversion circuits for single-current shunt sensor-less control. The Motion Control Engine executes the sensor-less field oriented control (FOC) algorithm in about 11micro-seconds, which is the key feature that enables simultaneous control of the fan and compressor motors as well as the PFC circuits. The IRMCF311 and the IRMCF312 are currently the only single devices in their class capable of simultaneously controlling all three systems.
The IRMCF3xx also includes an application layer processor that defines the operation of the air conditioning system independently from the MCE engine that controls the fan and compressor motors. Easy-to-use tools allow the engineer to evaluate controller performance and customize the algorithm with minimal effort, so the appliance engineer can focus his efforts on application issues rather than motor control functions.
Analog Section
The analog block consists of the IRS2136D family of three-phase analog driver and protection ICs. These ICs incorporate three independent 600V half-bridge inverter gate drivers with built-in bootstrap diodes. The protection functions include inverter over-current trip and under-voltage lockout with an automatic fault clear function. These analog gate drivers deliver parameter stability during product lifetime and parameter matching, such as propagation delay for high- and low-side channels, deadtime insertion. Separate power and signal ground connections enable a single DC line configuration on the low-side IGBTs for current sensing. Cross-conduction protection prevents accidental shoot-through to increase inverter reliability.
Power Stage
Finally, the new IRS2136D is designed to work with IR's extensive range of highly efficient depletion-stop trench IGBTs offered in a wide range of configurations, including discrete and integrated modules. Trench IGBTs have lower collector-to-emitter saturation voltage, VCE(ON) and total switching loss, ETS than punch-through (PT) and non-punch-through (NPT) IGBTs.
EN-Genius Says...
Given the huge slice of the energy pie that air conditioners consume, International Rectifier's IRS2136D variable-speed motor controller looks like a sure winner for both the environment and the manufacturer's bottom lines. Specifically designed for air conditioning applications, it includes the motor controller functions for both compressor and condenser fan along with power factor correction circuitry in a single, configurable solution. The result is a controller package that dramatically increases their motor's overall efficiency (94% - 95% from 1 kW to 3.5 kW) while cutting the manufacturer's total system cost.
The IRS2136D's combination of high integration and lowered BOM costs should help manufacturers move away from less efficient induction motors towards newer powered permanent magnet synchronous motors (PMSMs). Besides enabling PMSMs to deliver their natural 90+% efficiency, the intelligence packed into the IRS2136D also supports variable-speed operation, something that lets air conditioners run at longer, lower-power duty cycles. By running for longer times at much lower cooling levels a variable speed system can save up to 40% of the energy consumed by a comparable fixed-speed system while delivering greater comfort levels to the people being cooled. IR's clever controller also manages to squeeze out another 5% worth overall efficiency by including a function to advance the phase angle of the total applied current to create small amounts of field current that take advantage of the motor's inherent reluctance torque. Oh, did I mention that allowing the air conditioner to spend much of its time running at lower speeds means less noise and longer operating life?
 The press release above does a pretty good job of outlining the functional blocks within the controller, so I'll only use this space to expand on a few key points that make this platform approach to motor control such a good solution. As Fig. 1 illustrates, the controller consists of three separate blocks -- an 8051 microcontroller which handles housekeeping, configuration, and management, a custom motion control engine, and an analog sensing and conversion block. The two controllers are connected via a shared memory for efficient, low-overhead communications without complications of interrupt-driven systems.
|
 |
 |
|
Analog Function Blocks |
Combined Library Blocks Implement PWM/Current Sensing |
The motion controller block (the blue block in Fig. 1) is the system's crown jewel, which contains macro blocks of analog functions (see Fig. 2a) that can be interconnected to perform various tasks using a digital sequencing engine (see Fig. 2b). Executing these key functions at a low level gives it more equivalent processing power than a 32-bit RISC machine, allowing a single controller to run two (usually compressor and fan) motors and perform PFC simultaneously. IR has considerately provided a graphic interface programming tool that allows direct translation from a visual schematic to sequencer code. A library of tunable reference design elements for the analog control block should help you get your evaluation system up and running on its target application quickly.
 The motion controller programming software is part of a set of PC-based tools that support two completely separate development chains for the motion controller and the application code that runs on the 8051 core (see Fig. 3). While you'll still have to break out your C language skills to program the 8051, the code-free programming of the motion control engine should allow you to tweak your application to your heart's content and still bring your product to market in a fraction of the time than fooling with a conventional breadboard.
IR's controller solution should overcome much of the market resistance some HIVAC manufacturers have to PMSMs by simplifying the circuitry required to implement them. One of the big bugaboos is that PM motors normally require an external position sensor to time the current pulses to the rotor -- something that requires a second wire pair that adds to production and design complexities. Many low-cost PM controllers get around this by sequentially switching out one of the three the drive coils and using them as back-emf sensors, a solution that works but results in more noise and less efficiency. IR takes an alternate approach by using current sensing to estimate rotor position. This requires a more difficult calculation than back-emf, but it's well within the capability of the IRS2136D's configurable processor. The result is smoother torque control, quieter operation, and more efficiency, all without that pesky second pair of wires.
These little details tell me that IR has done its homework to tailor the controller to the meet the idiosyncratic needs of the air conditioning market while squeezing the last bit of efficiency and cost out of the design. But the capability of this innovative and flexible platform begs the question about its potential for other applications where cost, performance, and efficiency are at a premium. When I asked about this, my contacts at International Rectifier demurred on a definitive answer, but I'm willing to bet that we'll see several other incarnations of the IRS2136D targeted at both industrial applications and white goods within the next year.
The new iMOTION air conditioner platform is sampling. Pricing will vary by power levels and configuration. An example would be a controller plus three power stages for 2 kW input rating would be $19.95 in 100-k piece lots.
Product Page with links to all Data Sheets
|
