At low speeds, stepper motors exhibit a phenomenon known as magnetostriction, which results in an audible low-frequency hum. The noise is similar to the 50/60Hz hum that emanates from transmission lines and transformers.
Trinamic’s technology minimises this effect by implementing a PWM (pulse width modulation) algorithm that relies mainly on voltage modulation to control the motor at low speeds. It minimises the PWM current fluctuations which, the company says, are the main cause of the low-speed hum.
“Stepper motors used in automation must respect the needs of their human overlords,” suggests Trinamic’s r&d chief, Dr Stephan Kubisch. “The continuous noise of individual stepper motors in a laboratory environment may be rather distracting, and the din from hundreds of stepper motors in an industrial implementation can be deafening.
“Our customers asked Trinamic to perfect a commutation scheme for lower step frequencies that reduces noise,” he adds. “We made it self-tuning, easy-to-use and added an automated switch to transition to higher frequencies.”
Trinamic has implemented its noise-limiting technology in stepper motor drive chips which, it says, have demonstrated noise levels that are 10dB below those of traditional stepper motor chips.
The lower noise levels are expected to be a particular benefit when stepper motors are used close to human operators, and in video surveillance applications where nearby walls and ceilings can amplify noise levels. They could also be attractive for consumer applications such as home automation and air-conditioning, where users expect noise levels to be low.