Why Choose PMSM High Frequency Technology?

Why choose PMSM high frequency technology?

The most common motor type in the powertool industry is the traditional (carbon brush type) universal motor. High frequency refers to motors which run at a higher frequency than the conventional 50 or 60 Hz. High frequency power tools have much higher efficiency, meaning higher output for the same current input, and superior performance with lighter weight. All this combined with superior speed controllability and longer tool life make high frequency a fantastic choice when maximum performance is needed.

Highest possible efficiency

AGP’s permanent magnet synchronous motor technology (PMSM) has extremely high operational efficiency, high torque density, smooth torque delivery, and high dynamic performance under load. AGP is the one of the only manufacturers in the power tool industry employing this technology. AGP’s PMSM motors achieve an astounding 90% efficiency at full load, while competitors’ high cycle induction or switched reluctance (SR) motors on average achieve about 75%, and universal motors on average achieve about 60% efficiency.

Maximum power output and performance

As a result of its high output efficiency, the PMSM motor can make the most of the available current. For example, the output of the DM20 diamond core drill motor is over 3300 W on single phase 230 V 3700 W(16 A) input. For a typical universal motor to match that level of output, it would need almost 5500 W input, which would be 24 Amperes!

Highest power-to-weight ratio

In situations where it is crucial to make a tool as light as possible, a very small PMSM motor can achieve equal the power output as a much heavier universal motor, leading to astonishing weight savings. An example of this is the SB9 drywall sander. It is the lightest drywall sander in the industry, yet its 450 W PMSM motor puts out more power than a 650W universal motor.

Wide operational speed range

Universal motors lose a lot of power and easily overheat when their speed is electronically reduced by varying the voltage, severely limiting their usable speed range when maximum performance is required. A special characteristic of high frequency motors is that they perform very well when their speed is reduced, since the frequency is changed rather than the voltage, and this makes it possible to operate the motor at full load in a very wide speed range in any given mechanical gear ratio.

Totally enclosed construction

Universal motors need to have vents open to the environment to allow air flow to cool the motor. Inevitably, contaminants, such as dust, water or slurry will be sucked into the air inlets, shortening the life of the motor. A high frequency motor can be totally enclosed, with cooling flowing around the outside of the stator. They can either be air-cooled or water-cooled, and in either case, the inside of the motor will be totally enclosed. Water cooling is the most efficient cooling method.

Brushless for much longer life

Since high frequency motors are electronically commutated, they do not use carbon brushes, and this eliminates a key maintenance requirement and primary source of wear suffered by universal motors. This allows a high frequency motor to last about 10 times longer than a universal motor. High frequency motors can tolerate very long duty cycles under harsh conditions.  

Conclusion‍

The advantages of AGP’s PMSM high frequency motors are truly compelling. The only drawback to this technology is the unavoidable increased cost to produce them. The sophisticated control electronics and special rare-earth permanent magnet components are inherently expensive. Therefore, in cases where the special characteristics of high frequency are not needed, there will always be a need for power tools with universal motors and they will continue to be the most common type on the market.