“The use of motors and inverters continues to grow in applications such as industrial automation, robotics, electric vehicles, solar energy, white goods, and power tools. Accompanying this growth is the need to improve efficiency, reduce costs, shrink packaging, and simplify overall designs. While it is tempting to use discrete insulated gate bipolar transistors (IGBTs) to design custom motor and inverter power electronics to meet specific requirements, doing so is costly and delays design in the long run schedule.
The use of motors and inverters continues to grow in applications such as industrial automation, robotics, electric vehicles, solar energy, white goods, and power tools. Accompanying this growth is the need to improve efficiency, reduce costs, shrink packaging, and simplify overall designs. While it is tempting to use discrete insulated gate bipolar transistors (IGBTs) to design custom motor and inverter power electronics to meet specific requirements, doing so is costly and delays design in the long run schedule.
Instead, designers can use off-the-shelf IGBT modules to combine multiple power devices into a single package. These modules allow designers to develop compact systems with minimal interconnection, simplifying assembly, reducing time-to-market, reducing cost, and improving overall performance. With the use of suitable IGBT drivers, high-efficiency, low-cost motor drives and inverters can be developed using IGBT modules.
This article first briefly introduces motors and inverters and related drive circuits and performance requirements, then reviews the advantages of using IGBT modules and various module packaging standards, and finally introduces NXP Semiconductors, Infineon Technologies, Texas Instruments, STMicroelectronics and ON semiconductor manufacturers. Motor drive and inverter design options for IGBT modules and driver ICs, and how to apply them, including the use of evaluation boards.
Motor Type and Efficiency Standards
IEC/EN 60034-30 classifies motor efficiency into five levels, IE1 to IE5. The National Electrical Manufacturers Association (NEMA) has ratings ranging from “Standard Efficiency” to “Superior Efficiency” (Figure 1). In order to achieve higher efficiency standards, the use of Electronic drives is necessary. AC induction motors with electronic drive can meet the requirements of IE3 and IE4. In order to achieve the efficiency level of IE5, a combination of higher-cost permanent magnet motors and electronic drives is required.
Figure 1: Motor efficiency classes according to IEC/EN 60034-30 (IE1 to IE5) and corresponding NEMA classes (standard efficiency to ultra-high efficiency). AC induction motors with FOC and electronic drive can meet IE3 and IE4 class requirements. A permanent magnet motor is required to meet the IE5 efficiency level. (Image credit: ECN)
The development of low-cost microcontrollers (MCUs) has enabled designers to use vector control techniques, also known as field-oriented control (FOC). This is a variable frequency drive (VFD) control method in which the stator currents of a three-phase AC motor are treated as two quadrature components that can be visualized as vectors. A proportional-integral (PI) controller can be used to maintain the measured current component at its desired value. The pulse width modulation of the VFD defines the switching of the transistors according to the stator voltage reference which is the output of the PI current controller.
Originally developed for high-performance systems, FOCs are also increasingly attractive for low-cost applications due to their smaller motor size, lower cost, and lower power consumption. As low-cost, high-performance MCUs continue to be introduced, FOC continues to replace the lower-performance univariate scalar volts-per-hertz (V/f) control.
There are two main types of permanent magnet motors in use today, brushless DC (BLDC) and permanent magnet synchronous motors (PMSM). Both advanced motor designs require power electronics for drive and control.
Brushless DC motors are durable, efficient and low cost. PMSM motors have the characteristics of brushless DC motors, but with lower noise and higher efficiency. Both types of motors are commonly used with Hall sensors, but can also be used in sensorless designs. PMSM motors are used for applications requiring the highest performance levels, while BLDC motors are used for more cost-sensitive designs.
・Easier to control (6 steps) and requires only DC current
・ Torque ripple during commutation
・ Lower cost and lower performance (compared to PMSM)
・ Commonly used in servo drives with integrated shaft encoder
・ More complex control (requires three-phase sinusoidal PWM)
・ No torque ripple during commutation
・ Higher efficiency and higher torque
・ Higher cost and higher performance (compared to BLDC)
The efficiency of an inverter indicates how much DC input power is converted to AC power at the output. A good quality sine wave inverter can provide 90-95% efficiency. Lower quality modified sine wave inverters are simpler, less expensive and less efficient, typically 75-85%. High frequency inverters are generally more efficient than low frequency designs. The efficiency of the inverter also depends on the inverter load (Figure 2). All inverters require power electronic drive and control.
Taking photovoltaic inverters as an example, there are three types of efficiency ratings:
NO.1 peak efficiency
Indicates the performance of the inverter at optimum power output. It shows the peak of a particular inverter’s performance curve and can be used as a criterion for its quality (Figure 2).
NO.2 European efficiency
Consider a weighted number of how often the inverter is used at different power outputs. It is sometimes more useful than peak efficiency because it shows how the inverter behaves at different output levels during the solar day.
NO.3 California Energy Commission (CEC) Efficiency
This is also a weighted efficiency, similar to the European efficiency, but it uses a different weighting factor assumption.
The main difference between European efficiency and CEC efficiency is that the former is based on data from Central Europe and the latter is based on data from California. The importance assumptions for each power level are different for a specific inverter.
Figure 2: Typical inverter efficiency curve showing peak efficiency point. (Image credit: Penn State University)
The basic function of an IGBT is to switch current as quickly as possible with the lowest possible losses. IGBT is the English writing of Insulated Gate Bipolar Transistor. As the name suggests, an IGBT is a bipolar transistor with an insulated gate structure, and the gate itself is basically a MOSFET. Therefore, IGBTs combine the advantages of high current-carrying capacity and high blocking voltage of bipolar transistors with the capacitive, low-power control advantages of MOSFETs. Figure 3 depicts how MOSFETs and bipolar transistors are combined to form an IGBT.
Figure 3: Conceptual structure of an IGBT showing the structure of a MOSFET forming an insulated gate and a bipolar transistor as part of the power processing. (Image credit: Infineon Technologies)
The basic operation of an IGBT is simple: a positive voltage UGE is applied from the gate (G in Figure 3) to the emitter (E) to turn on the MOSFET. The voltage connected to the collector (C) can then drive the base current through the bipolar transistor and MOSFET; the bipolar transistor is turned on and the load current can flow. When the voltage UGE≤0V, the MOSFET is turned off, the base current is interrupted, and the bipolar transistor is turned off at the same time.
Although simple in concept, developing the hardware (gate drivers) to control IGBTs can be a complex task due to the many performance nuances in actual devices and circuits. Most of the time it is not necessary. Semiconductor manufacturers offer many suitable gate drivers as integrated solutions with a variety of functions and capabilities. Therefore, it is very important to match the appropriate gate driver for the IGBT module.
IGBT modules are available in a variety of package types (Figure 4). The largest specification is rated at 3,300 volts or more and is designed for use in megawatt-scale installations such as renewable energy systems, uninterruptible power supplies and oversized motor drives. Medium-sized modules are typically rated at 600 to 1700 volts and are suitable for a variety of applications including electric vehicles, industrial motor drives and solar inverters.
Figure 4: IGBT modules are available in a variety of packages. Typical voltage ratings range from 600 volts to 3300 volts. (Image credit: Fuji Electric)
The smallest devices, called integrated power modules, are rated at 600 volts and can include built-in gate drivers and other components for motor drives in small industrial systems and consumer white goods. Compared to other types of power switching elements, IGBTs achieve higher power levels and lower switching frequencies (Figure 5).
Figure 5: Power range versus switching frequency for common power switching devices (Image credit: Infineon Technologies)
IGBT Module Evaluation Board for Traction Inverters
For designers of high voltage traction inverters, NXP Semiconductors offers the FRDMGD3100HBIEVM gate driver power management evaluation board featuring its MC33GD3100A3EK half-bridge gate driver IC. This evaluation board is specially designed for use with Infineon’s FS820R08A6P2BBPSA1 IGBT module (Figure 6). It is a complete solution including a half-bridge gate driver IC, DC Link capacitors and a converter board for connecting to a PC that provides control signals. Target applications include:
・ Electric vehicle traction motors and high-voltage DC/DC converters
・ Electric vehicle on-board chargers and external chargers
・ Other high voltage AC motor control applications
Figure 6: NXP’s FRDMGD3100HBIEVM gate driver power management evaluation board connected to Infineon’s FS820R08A6P2BBPSA1 IGBT module, also showing the MC33GD3100A3EK, half-bridge gate driver IC, DC Link capacitors, and converter board for connecting to a PC that provides control signals Location. (Image credit: NXP Semiconductors)
Driver for 150mm x 62mm x 17mm IGBT modules
For designers of motor drives, solar inverters, HEV and EV chargers, wind turbines, transportation, and uninterruptible power systems, Texas Instruments developed ISO5852SDWEVM-017 (Figure 7). It is a compact dual-channel isolated gate driver board that provides the required drive, bias voltage, protection and diagnostics for general purpose half-bridge silicon carbide (SiC) MOSFET and silicon IGBT modules in a standard 150mm × 62mm × 17mm package Function. This EVM from TI is based on the ISO5852SDW 5,700Vrms reinforced isolation driver IC in a SOIC-16DW package with 8.0mm creepage and clearance. This EVM includes an isolated DC/DC transformer bias supply based on the SN6505B.
Figure 7: Texas Instruments ISO5852SDWEVM-017 dual-channel isolated gate driver board mounted on top of a 150mm × 62mm IGBT module. (Image credit: Texas Instruments)
Smart Power Module Evaluation Board
The STEVAL-IHM028V2 2,000-watt three-phase motor control evaluation board from STMicroelectronics (Figure 8) uses the STGIPS20C60 IGBT smart power module. The evaluation board is a DC/AC inverter that generates waveforms for driving three-phase motors such as induction motors or PMSM motors in HVAC (air conditioners), white goods, and high-end single-phase power tools up to 2000 kW watt. Designers can use this EVB to implement FOC designs for three-phase AC motors.
The main part of this EVM is a general-purpose, well-evaluated dense design consisting of a three-phase inverter bridge based on a 600-volt IGBT smart power module in an SDIP 25L package, mounted on a heat sink. This smart power module integrates all power IGBT switches with freewheeling diodes and high voltage gate drivers. This level of integration saves PCB space and assembly costs and helps improve reliability. The board is designed to be compatible with single-phase power supplies from 90 to 285 volts AC and is also compatible with 125 to 400 volts of DC input.
Figure 8: STMicroelectronics STEVAL-IHM028V2 product evaluation board with FOC. The board can be used to evaluate a wide range of applications such as HVAC (air conditioning), white goods, and high-end single-phase power tools. (Image credit: STMicroelectronics)
850-watt evaluation board that can handle multiple motor types
The SECO-1KW-MCTRL-GEVB evaluation board from On Semiconductor enables designers to control different types of motors (AC induction motors, PMSM, BLDC) by using various control algorithms including FOC via the Arduino Due pins This is done by connecting the microcontroller to the socket (Figure 9). The board is designed to be used with an Arduino DUE (header compatible) or similar controller board with an MCU. With integrated power modules and power factor correction, the board is designed to support developers from the very first steps of designing an application for use by designers of industrial pumps and fans, industrial automation systems, and consumer appliances.
Figure 9: Block diagram of the On Semiconductor SECO−1KW−MCTRL−GEVB evaluation board (Image source: On Semiconductor)
Based on the NFAQ1060L36T (Figure 10), this evaluation board is an integrated inverter power stage consisting of a high-voltage driver, six IGBTs, and a thermistor, suitable for driving PMSM, BLDC, and AC induction motors. Among them, the IGBT adopts a three-phase bridge configuration, and the emitter connection is separated from the lower pin, which has the greatest flexibility in the selection of control algorithms. The power stage features a full range of protection features, including cross-conduction protection, external shutdown, and undervoltage lockout. An internal comparator and reference connected to the overcurrent protection circuit allows the designer to set its protection level.
Figure 10: On Semiconductor’s NFAQ1060L36T Power Integration Module functional block diagram (Image source: On Semiconductor)
Summary of NFAQ1060L36T power integrated module features:
・ Three-phase 10A/600V IGBT module with integrated driver
・Compact 29.6mm x 18.2mm dual in-line package
・ Built-in undervoltage protection
・ Cross conduction protection
・ ITRIP input turns off all IGBTs
・ Integrated bootstrap diode and resistor
・ Substrate temperature measurement thermistor
・ Shutdown pin
・ UL1557 certification
Summary of this article
Designing custom motor and inverter power electronics using discrete IGBTs can meet specific requirements, but in the long run, it is costly and delays the design schedule. Instead, designers can use off-the-shelf IGBT modules to combine multiple power devices into a single package. These modules allow designers to develop compact systems with minimal interconnection, simplifying assembly, reducing time-to-market, reducing cost, and improving overall performance.
As shown above, designers can use IGBT modules with suitable IGBT drivers to develop low-cost, compact motor drives and inverters that meet performance and efficiency standards.