Our first installment in the "Basic Knowledge" edition of Tech Web Motor is this introduction to "Motor Driving".
In recent years, worldwide annual production of motors has been in the vicinity of ten billion units, and the power consumed by motors is said to account for roughly 50% of total global electric power consumption. These may sound like preposterous numbers, but when one begins to count all the various motors one uses regularly--from the motors in the hard disk drives and optical drives as well as the cooling fans of PCs, to the many motors used in washing machines, refrigerators, air conditioners, hybrid vehicles, and on and on--they likely begin to seem reasonable. And as one example of new measures to address environmental problems, it has been expressly stated that automobiles will be electrified, primarily in Europe and North America, so that demand for motors is strongly trending upwards.
On the other hand, strict energy conservation regulations have been established to address global energy issues, and as a matter of course, energy-saving measures for equipment using motors is a vital concern. In addition to energy conservation of the motors themselves, highly efficient motor driving and control methods are also immensely important.
As explained above, motors are used in various fields and in diverse applications. Thus there are many types of motors, and also many kinds of motor driving and control methods. In this Basic Knowledge edition of Tech Web Motor on "Motor Driving", we explain the basic of motors and describe various motor driving methods.
We begin by describing four features that have been required of motor drivers in recent years. In this segment, we will subsequently proceed to discuss actual motor driving while keeping these features in mind.
Motor drivers must be provided with functions to protect motor driver ICs from abnormal voltages and currents, functions to prevent malfunctions due to power supply voltage drops, and other protection functions. They are also required to secure safety through current-limiting functions to control motor currents during motor startup or forced shutdown, when being restrained, etc., as well as functions to report fault conditions to an external host processor or other device.
In order to reduce power consumption of a motor, power devices and driving technology capable of low power consumption are needed. For example, by using an automatic lead angle adjustment function or the like, high efficiency can be obtained over a broad range of rotation rates, from low- to high-speed rotation.
Optimization of the driving waveform is important to address noise and vibrations during motor operation. The commutation technology that is optimal for the magnetic circuit of various types of motor must be used according to the field of application, whether this is the optimal commutation technology (120°, 150°, sine wave) for a brushless DC motor driver, or a soft start technique for a fan motor driver, or a current attenuation method (decay technique) for a stepping motor driver.
Digital rotation control technology for motors using FLL (frequency locked loop) and PLL (phase locked loop) control, as well as high-precision positioning control technologies needed for actuators, and other highly efficient driving control algorithms are indispensable to the development of high-performance motor applications. There are demands for high-efficiency driving control algorithms that can easily be utilized by designers, for example by incorporating hard logic for control algorithms in driver ICs. Moreover, compatibility between driver ICs improves convenience of use. Improving convenience is important when specification changes occur during development, for example by enabling substitutions without changing the PCB layout of the motor driving control board.
・The global demand for motors is strongly trending upward.
・Due to global energy issues, high-efficiency motor driving and control methods are extremely important.
・Four features are demanded of motors: high reliability, low power consumption/high efficiency, quietness/low vibration, and control/convenience.