Digital Speed Controller for Embedded High Reliability Applications

Modern “electric platform” based vehicles and aircraft for commercial and military duty are using electric motors in large numbers. The demand for higher efficiency, improved performance, lower noise and smaller controller footprint has led to development of a high reliability motor controller for vector controlled permanent magnet motors. This controller is optimized to act as a design platform, with an interface that maps a comprehensive register set to dozens of drive parameters to allow quick setup and testing. IR’s iMotion® components are used which are highly integrated yet low cost processors, gate drivers, and feedback electronics, assembled into a relatively small circuit board stack mounted on top of a power substrate. A dedicated hardware processor with embedded pre-configured sinusoidal FOC algorithm supports high reliability applications such as pumps, fans, and compressors. This paper discusses the ease of commissioning the controller starting with basic motor and application parameters; no software is required. This allows the user to quickly create a high performance adjustable speed machine with high starting torque, accurate speed control over a wide 20:1 speed range, and capability of high inverter frequency. Test data from a test stand is given and test data from a pump application is shown. Electric Platforms Require Small Embedded Motor Controllers with Efficient Algorithms Modern Electric Platforms are replacing gear driven auxiliary loads with generator fed electric motors that have POL power conditioning to provide the required motor buses. (5). An example of this is the 787 aircraft which has deleted the bleed-air system traditionally used and replaced it with localized electric motors for such loads as environment control, hydraulic cooling, and APU starting. Another example is the RST-V reconnaissance, surveillance, and targeting vehicle being developed for the US Marines which uses permanent magnet motors for a number of applications including hub mounted traction drive, electric power steering, and drive-by-wire. An on-board generator for produces 27KW for onboard loads and off board use. Nowadays, system Integrators are being asked more frequently for an electric driven solution which uses permanent magnet motors because of their high torque to amp ratio, efficiency, and improved power factor. Weight is a penalty in transportation, especially in aircraft, which makes thermally efficient hybrid substrate packaging the preferred approach for power electronics. The algorithm used should allow efficient utilization of motor supply voltage and current. Jay Goetz Sr. Staff FAE International Rectifier High Reliability Products Minnetonka, MN [email protected] Weiping Hu Design Engineering Manager International Rectifier High Reliability Products Leominster, MA [email protected] Deb Bhattacharyya Sr. Hybrid Electrical Design Engineer International Rectifier High Reliability Products Leominster, MA [email protected] Flexible Integrated Motion Control Platform Two design platforms are being created for High Voltage (600V IGBT silicon) and Low Voltage (100V Mosfet silicon) control of permanent magnet motors. A design platform differs from a product in that it contains additional interfaces for communication, discrete/stand-alone control, and has some flexibility in the housekeeping power supply and in the motor bus conditioning. Figure 1 shows the platforms which have these options: Figure 1a High Voltage Platform Figure 1b Low Voltage Platform Important technical features include (1): • Sensorless – no hall sensors or position feedback required for commutation • Selectable Power Electronics – IGBT or MOSFET Power Stage, optimized for desired load and Vbus ratings • Adjustable Performance – speed and current loops with adjustable gains, and adjustable PWM period and deadtime • Varied motor usage – can accommodate PM motors with a wide range of parameters (inductance, speed, Ke/Kt, #poles) • Configurable startup sequencing and operation • Protections with override – bus over-undervoltage/overcurrent/improper supply voltage/substrate temperature/loss of phase/under-overspeed Validation of mature iMotion technology in high volume markets before use in Aerospace and Military applications eliminates much uncertainty in designs which use it. Before the products described in this paper were developed, the iMotion chipset has already been designed-in and used in dozens of products including factory automation machines, white goods, and automotive controls. In fact, these chipsets have been designed into speed and position controls onboard commercial and military aircraft and land vehicles such as compressors, pumps, fans and weapons positioning. Alhough the above characteristics are important in Aerospace and military applications, High Reliability Products also need: • (More) Robust Functionality • Ruggedized Packaging suitable for Embedding in “tight” locations • Small footprint suitable for cold-wall or heat sink mounting • Adaptable to different motors and applications • Mil Qualification and Screening • Long-term Availability • Strong(er) Customer Support Figure 2) shows an architecture which is scalable and is partitioned to meet these goals. Gate Drive, Sensor Interface Control Section with Isolation System Controller: System Sequencing Fault Response Speed Control External Loop Control Analog & Discrete Interface Integrated Platform Application Interface