POWER
The sine of technology to come T
How a pure sine wave output can make all the difference to the MTBF, noise and effi ciency of electric motors
he need to rapidly achieve Net Zero is vital to prevent further climate change. One critical way is to reduce the energy wasted by electric motors. As the International Energy Authority said, ‘Electric motors are the largest single-energy use with half of global electricity consumption. There is a huge, untapped potential for energy effi ciency in motors.’ A British company, QPT, is dedicated to solving this. Its technology switches the transistors in the Variable Frequency Drives (VFDs) that control electric motors much faster, so less energy is wasted. Silicon transistors today switch at a few kHz, SiC and most GaN in the 50-10kHz range, but QPT
uses new qGaN technology to enable GaN transistors to switch at 1MHz. This reduces the losses in the drive, but QPT also removes unwanted high frequency noise in the output to leave an almost perfect, pure sine wave, which is much better for the motor. High frequency switching and ‘fast GaN’ has usually been rejected for power applications because of concerns on thermal issues and interference, but by combining techniques from radio frequency (RF) engineering and power electronics, QPT has solved these problems.
The output of traditional drives is a PWM (Pulse Width Modulation), high voltage, digital
signal with a ‘noisy’ output and a lot of high frequency components. There is signifi cant energy in these harmonics which is wastage. In contrast, a pure sine wave output brings signifi cant benefi ts. The most obvious is the energy savings. Because there is no high frequency energy, the eddy currents and losses within the motor are substantially reduced. Combined with the qGaN technology that cuts waste within the VFD, the total energy saving for the system is between 10 and 20 percent depending on the application. Given how much electricity is used globally by motors and how that is increasing, this is a substantial opportunity.
Fig 1 shows the frequencies that GaN can be driven at. If the overheating and RF issues are solved as QPT has done, then signifi cantly higher frequencies become possible.
42 OCTOBER 2024 | ELECTRONICS FOR ENGINEERS
The waste is not only heat; the harmonics affect the motor, making it not run smoothly with ‘cogging”, vibration and noise. A pure sine also has no dV/dt, a sudden change in voltage from sharp edges of the PWM, so there is less stress on the windings, while the absence of bearing currents also helps improve reliability. Rupert Baines, QPT’s CEO, said, “There is no other technology that can achieve energy saving of this magnitude. Given the importance of net zero for the planet, this really matters. Global adoption of our technology for heat pumps, industrial motors, HVAC, robotics and electric vehicles is a practical way to cut CO2 production and achieve our mission of helping the planet.”
www.q-p-t.com
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