Hits:Updated:2020-04-14 09:04:34【Print】
Signal and power isolation help ensure stable operation of the AC motor drive system and protect the operator from the danger of high voltage.
But not all isolation technologies can meet all requirements, especially in terms of device life and temperature performance.
To address the design challenges of alternating current (AC) motors, this white paper compares Texas Instruments ’capacitor-based isolation technology with traditional isolation technology, including isolation gate drivers isolated in power stages, isolation voltage, current feedback, or control modules Digital input.
What is an AC motor drive system?
AC motor drive is an induction motor that uses AC power input. As shown in Figure 1, it can drive large industrial loads, such as heating, ventilation, and air conditioning of commercial buildings, pumps and compressors.AC motors can also drive factory automation and industrial device loads that require speed regulation, such as conveyor belts or tunneling, mining and papermaking equipment.
The AC motor drive uses AC energy, rectifies it into a DC bus voltage, implements a complex control algorithm, and then converts the DC power back to AC power through a complex control algorithm based on load demand.
Isolation in AC motor drives
Motor drive systems such as AC motor drives contain high voltage and high power levels; therefore, measures must be taken to protect operators and key components of the entire system.
In addition, critical system components, such as controllers and communication peripherals, need to be protected from high power and high voltage circuits in motor drives.According to the definition of the International Electrotechnical Commission 61800-5-1 safety standard, the insulation between circuits can be realized by the semiconductor integrated circuit (IC) isolation at the component level.
Isolation ICs can transfer data and power between high and low voltage units, while preventing any dangerous DC or uncontrolled transient currents.Generally, an isolator provides the required level of insulation within a circuit through an isolation barrier.The barrier separates high voltage from human-accessible parts.
Isolation in AC motor drives
Designers have multiple choices when implementing isolation barriers in AC motor drives, but for the past 40 years, the most commonly used device for galvanic isolation in systems has been the optocoupler, also known as an optoisolator or optocoupler.Although optocouplers are cost-effective and ubiquitous, they do not provide the same level of temperature performance or device life as the latest isolation methods.
TI's capacitive isolation technology integrates enhanced signal isolation in capacitive circuits that use silicon dioxide (insulation on the base chip) as a dielectric.Unlike optocouplers, it can integrate the isolation circuit with other circuits on the same chip.Isolators manufactured through this process have reliability, shock resistance, and enhanced isolation, equivalent to two basic isolation levels in a single package.
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