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Portable Ventilators & the Advanced Design of Brushless DC Motors

Thu, 04/25/2013 - 5:07pm
Michael Bloom, President, Sinotech

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Advances in the brushless DC motor have saved the lives of countless patients in ways that weren’t possible just 25 years ago. The BLDC motor is a synchronous electric motor that has coils wound around the stationary lamination stack of a stator—not a rotating armature—and magnets mounted on a rotor. This basic design has allowed engineers to create BLDC motors small enough to fit into portable ventilators used in hospitals, emergency vehicles, and homes.

A Brief History of Ventilators
The first ventilators invented in the 1830s were “iron lungs,” a negative pressure ventilator used during the polio epidemic in the United States. A non-sparking, variable-speed brushless DC motor, however, wasn’t commercially available until much later.

World War II prompted the need for innovations in BLDC motors and ventilator technology, as pilots needed breathing assistance at high altitudes. Such innovations led to the invention of John Haven Emerson’s medical ventilator, which Harvard University used in its anesthesia department.

The Bird Mark 7 ventilator gained attention in 1955 because it was operated by a pneumatic device rather than an electrical power source. By the early 1970s, the SERVO series of ventilators introduced a line of smaller, quieter, and more efficient devices. In 1991, thanks in part to BLDC motor advancements, medical engineers were finally able to design a single ventilator with rapid flow trigger response that hospitals could use with all patients—from adults to preemies in the neonatal unit.

Modern Portable Ventilators
Today’s brushless DC motors in portable ventilating systems offer optimal thermal management and the continual delivery of air without affecting speed or pressure. Portable ventilators also offer the following benefits:

  • User-defined breath per minute rates
  • Infection control
  • Positive end-expiratory pressure (PEEP)
  • Standalone operation
  • Battery power and energy efficiency
  • Alarms that indicate high airway pressure, low battery life, loss of power, and loss of breathing circuit integrity
  • Indicator accuracy

Brushless DC motors can run at higher speeds than their brushed counterparts. Because of the brushless aspect of the gear motor, there is no risk of sparking, which is ideal in oxygen-rich environments. Furthermore, brushless motors are quieter and can last up to ten times longer than brush-type motors.

Flat BLDC Motors
As the demand for convenience grows, particularly with regard to portable ventilators, the sizes of BLDC motors have become even smaller. The motors allow high torque even in portable devices with small profiles. Flat brushless motors have thin profiles and a multi-pole, external rotor. The shaft on the outside of the motor rotates as the flange remains stationary. As more pole pairs are added to the motor, it gains more torque.

Cylindrical Brushless DC Motors
To accommodate small motor size requirements and high speeds, engineers have designed slotless cylindrical motors with small diameters that work in a pressure-controlled and bi-level controlled mode. The size of the cylindrical motor is so small (as small as 22 mm in diameter) that manufacturers can use it for everything from simpler breathing disorder treatments to life-saving invasive therapies in the ICU. Experts expect future cylindrical models to offer better speed and torque capabilities, as well as optimized lamination materials and coils to keep temperatures cooler.

The genius of the BLDC motor is that manufactures can custom-make them to meet specific medical needs, with options such as front flanges, bearing upgrades, and motor sealing. As technologies in BLDC motors and portable ventilators advance, home care applications and therapies will become more available to the public, and emergency workers will be able to save more lives in the field.

For more information, visit www.sinotech.com.

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