Size reduction and efficiency gains for PMW internal rotor brushless motors
Published: 14 June 2019 - Sarah Mead
Thanks to a systematic redesign, IR9 internal rotor brushless motors from Printed Motor Works are now shorter, lighter and have enhanced efficiency. The new versions are also constructed from fewer components that are simpler to machine.
Lamination is used in the rotor stack assembly, producing greater efficiency, particularly at higher speeds. The rotor assemblies can also be specifically balanced for higher speeds.
For improved cooling, windings can be encapsulated, with a direct thermal path to the front plate for more effective heat sinking.
The IR9 motors can be fitted with a compact, rugged magnetic encoder for commutation or encoder functions, without increasing the overall length of the motor or adding an external cover. The shaft mounted magnet gives positional emulation of hall switches for motor commutation as well as direction and speed feedback, with 12 bit resolution of rotor position by 4069 counts per revolution.
A further option is an electromagnetic brake within the motor casing. This does not significantly increase the overall motor length or require a separate external cover.
Basic IR9 motors typically have a peak torque of 2 Nm, a rated speed of 3500 rpm and a nominal operating voltage of 62 V. They can be custom designed to a client's precise specification, and are wound specifically for the voltage and current supply required. They are modelled electromagnetically to optimise the internal motor components for the speed, torque, duty cycle, type of cooling and lifetime of the application.
Optimisation strategies are typically based on minimising weight and maximising efficiency, but they can also be based on other constraints if required such as minimising current, torque ripple etc.
Possible applications include marine winch systems, bomb disposal robots, industrial automation, fan drives and paper handling, in sectors such as robotics, materials handling, medical, industrial automation, aerospace and defence.
A range of shaft options is available, including hollow, flanged, keyway(s), spline and plain. Hollow shaft motors can be used in applications such as radar / waveguide systems or to transfer liquids or power.
PMW can be found at www.printedmotorworks.com.