In December 2024, Monica Cintron, the Marketing Manager at Astrodyne TDI, and Anil Kurugode, a Field Application Engineer for Astrodyne TDI's central region, presented a webinar on the importance of choosing power supplies for medical systems.
Discover their findings and the requirements for power systems in medical applications.
Astrodyne TDI has more than 60 years of experience in the power industry. With over one thousand employees in factories in China and Malaysia and our local Hackettstown, New Jersey office, we develop and manufacture power supplies, electromagnetic interference (EMI) filters and isolation transformers.
First, Cintron and Kurugode discussed the insights Astrodyne TDI has gained working with health care customers.
The vast majority of modern medical equipment requires stable and reliable power. The global health care industry is massive and rapidly growing, and technology is constantly changing the way medical devices are designed, qualified and used. What was once interference is now a necessity. This includes Wi-Fi, Bluetooth and other forms of connectivity that may arise in the future.
Recognizing that the medical devices industry is constantly evolving and innovating is important. The market is worth more than $518 billion, and the fundamentals never change — even as robotics and artificial intelligence enter the picture. Safety, electromagnetic interference (EMI), emissions and regulatory aspects remain constant.
According to Kurugode, power systems for medical applications have the following general requirements:
Providing stable power begins with input power, which is converted to various voltages — typically direct current (DC) voltages — for all subsystems. An EMI filter filters out high-frequency alternating current (AC) noise while allowing the necessary DC to pass through. Occasionally, a backup battery is involved, too, which needs to blend seamlessly into the system.
While these power concepts are basic, Kurugode says that the medical world adds complexity because of the patient and operator aspect. To provide stable power, power systems for the medical industry must:
This final point involves equipment and power supply classifications. Defining a proper class of equipment is critical. We discuss this in greater depth later.
The medical world is unique because patients are more vulnerable and unable to respond to hazards — while the risk to body, life and property is always a concern with power systems, the consequences of failure are much higher in the medical field.
Additionally, in an industrial sector, trained personnel operate equipment and can handle any faults that arise. However, medical industry operators do not typically have the same technical background or technical expertise as engineers. So, equipment designed for medical use must consider these differences in experience to keep operators safe and avoid accidental contact.
Classification standards are essential for safety when dealing with medical devices.
The International Electrotechnical Commission (IEC) defines standards specific to the medical field. IEC 60601-1 governs safety and performance requirements for medical electrical equipment. This standard eliminates much of the worry about definitions, classes of equipment and control standards.
IEC 60601-1 is the general standard for medical electrical equipment, such as X-rays, ultrasound machines, dialysis machines, ventilators and blood pressure monitors. It is further divided into several parts, including:
Safety standards differ in the industrial world. In the medical field, the IEC 60601-1 standard clearly specifies acceptable levels of performance for various equipment classes.
IEC 60601-1 classifies applied parts — equipment that comes in contact with a patient — further into body (B), body floating (BF) and cardiac floating (CF) categories. The most benign operation mode (B) occurs when a patient is monitored without electrical contact. BF devices have physical connections to the patient. CF devices have direct contact with the heart or bloodstream. Here are a few examples:
Because these applied parts come into contact with the heart or bloodstream, cardiac floating requirements are the strictest and the least allowed leakage.
Next, Kurugode discusses selecting the proper equipment class in greater depth. Equipment is categorized according to the method of protection against electric shock:
Next, Kurugode covers insulation and isolation, reinforcing that the most critical parameter for safety is the risk of electric shock. The person at the receiving end should never receive a shock, and this is accomplished with an insulation system.
Kurogode gives the example that if the primary live circuit (wall power) is 120 or 230 volts, the insulation system must be able to withstand about 20 times that voltage. Here's some more information from the presentation.
Operational insulation, or functional insulation, is not designed to protect users from shocks but helps prevent short circuits between components within a device.
The equipment connected to the earth circuit requires one level of basic insulation, or one Means of Protection (MOP).
SELV circuits must be separated from hazardous voltages by two levels of protection (two MOPs). These circuits are designed to be safe even if touched.
The two levels of insulation may be double insulation, which involves basic and supplemental insulation, or reinforced insulation, which is a single layer that provides the same level of protection as double insulation. If one layer fails, the other should remain intact to ensure safety.
If you have SELV circuits and the outlets are completely uncommitted, meaning the return is not earthed, you can feel free to earth it. However, the system designer must ensure that this connection is functional and safe.
Clearance and creepage are essential for separating hazardous and safe circuits. These parameters are nonnegotiable for certain classes of equipment. They describe the shortest distance between two conductive parts, measured along the surface of an insulator (creepage) or through the air (clearance).
Kurugode next summarized these general safety requirements:
Safety considerations are well-defined and nonnegotiable. Electromagnetic compatibility considerations are also critical to ensure devices are not affected by EMI.
EMC includes both emissions and immunity — the electromagnetic energy released by a device and the device's ability to withstand interference from external electromagnetic sources. The primary standard for EMC is IEC 60601-1-2. Meeting this standard is crucial to:
The Food and Drug Administration (FDA) governs products in the United States. There are three medical device classifications according to the FDA:
Voltage and structural requirements differ in Europe. However, both regions prioritize safety and efficacy.
Medical-grade products clearly state their certifications on their labels. For example, labels will reveal:
Purchasing certified products reduces the burden on the purchaser, as the manufacturer has already ensured safety. However, insulation systems can sometimes break down due to factors like aging, humidity, pollution and lightning, so remaining vigilant about potential breakdowns is vital. Double or reinforced insulation is extremely beneficial should the system fault.
Isolation transformers help manage the leakage current in complex systems. They connect to mains power and provide safe, isolated output, reducing the leakage current downstream. They are compact, efficient and available in various ratings, making them suitable for diverse applications.
At Astrodyne TDI, our isolation transformers offer the following features:
EMI filters also help ensure compliance and minimize interference in medical devices. Astrodyne TDI's complete line of off-the-shelf filters is available in medical-grade versions. Applications for these devices include:
All filters are approved to meet the leakage current requirements of diverse environments.
We offer a range of products tailored for various medical applications. Our systems are designed with safety and compliance in mind and meet rigorous health care industry standards.
If you have any questions about our products or need assistance, reach out through our website today. You can also find a rep or shop power supplies online.