Toshiba Improves Stepper Motor Efficiency with New Drivers
Edis Osmanbasic posted on February 22, 2019 |

Because of the widespread use of stepper motors, motor makers are constantly searching for ways to improve the efficiency of stepper motors, thus reducing their heat and energy. Now, Toshiba has developed a unique technology for bringing new efficiency to these common components.

A stepper motor. (Image courtesy of Wikimedia user Dolly1010.)
A stepper motor. (Image courtesy of Wikimedia user Dolly1010.)

A stepper motor is a brushless DC electric motor. Its full rotation is divided into a number of equal steps. The motor moves one step when the direction of current flow in the field coil changes, reversing the magnetic field of the stator poles. Stepper motors are able to produce high torque at low rotor speed with minimum vibration. They’re known for their stable and highly accurate positioning, making stepper motors suitable for numerous applications, such as printers, robotics, antennas, industrial equipment, etc.

Stepper motors require sufficient current margin at all times in order to provide stable operation and avoid stalling. The current margin is adjusted to provide reliable operation at peak torque. Stepper motors rotate in synchronization with pulses. Stalls are caused by the instant overloads or rapid speed changes triggering loss in synchronization, thus the motor stops while still running at peak current. Since current is adjusted to a constant value, significant power is lost and dissipated as heat when the torque is light. Current management involves quite a complex system and requires additional electronics, microcontrollers and sensors by using a real-time torque monitoring and current feedback.

Toshiba has developed an innovative solution to avoid these problems: Active Gain Control (AGC) technology, which automatically optimizes the current necessary to drive a stepper motor according to the required load torque. Current is adjusted even in the case of a small amount of torque, eliminating the additional current necessary to keep the minimum margin to operate efficiently.

The figure below illustrates how the AGC technology saves energy and increases the motor efficiency by smart controlling the motor current and still provides sufficient current margin for reliable motor operation. This dedicated integrated circuit has dramatically simplified stepping motor driving as well.

Motor drive current optimized using AGC technology(Image courtesy of Toshiba.)
Motor drive current optimized using AGC technology(Image courtesy of Toshiba.)

The tests performed by Toshiba engineers confirmed improved efficiency, saved energy and reduced heat when AGC technology was used. Operating temperature was reduced by 30  (from 71.1  to 41.1  ) and motor drive current was reduced up to 30 percent resulting in energy savings of 40 percent.

Heat dissipation from the motor recorded by a thermal camera.(Image courtesy of Toshiba.)
Heat dissipation from the motor recorded by a thermal camera.(Image courtesy of Toshiba.)

Toshiba’s AGC technology provides important advantages for both motor manufacturers and users. This solution allows a simpler design for motors and regulating circuits. The most important benefit is a significant reduction in motor current and energy consumption. The result is 40 percent less heat generation. This improvement is important for specific stepper motor applications in which the motor is placed inside housing where heat dissipation is quite demanding.


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