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Leakage current is a term used to describe current that is non-functional. Current that flows from either a DC or AC circuit to the ground, a chassis or any other conductive component in the absence of a grounding system is considered leakage current. Leakage current from the input or output cannot be avoided, but it must be controlled. There are specific limits for leakage current, depending on the industry or application.
Leakage current in different types of equipment flows when there is an electrical connection between the ground and a conductor, which has not been designed intentionally. If the equipment you are using is not grounded correctly, current will flow through other energized components or conductors. In the case of electrical devices, leakage current usually occurs as a result of faults in insulation or the fabrication of materials used to make parts, such as semiconductors.
Controlling leakage current is important for several reasons. Most electrical installations and equipment utilize grounding systems to protect against outages and hazards. In cases where there are faults or failures in the insulation between power lines and conductive parts, or the grounding connection is disrupted, current flow can cause a circuit breaker or a blown fuse. There is also a risk to human safety, particularly when using medical equipment.
There are standards in place to enhance safety and reduce risks. When using equipment and devices, it is critical to ensure that you are aware of permissible leakage current levels for the relevant application. It is important to note that limits are stricter and more rigorous for medical equipment.
Electrical equipment is increasingly commonplace within clinical settings. Electricity plays an essential role in enhancing treatment outcomes and saving lives, but using medical equipment can pose risks. Medical power supplies need low leakage current, and there are stringent guidelines in place. Medical equipment leakage current limits are significantly lower than non-medical equipment. This is a safety measure, which is used to protect both healthcare teams and patients.
In many parts of a hospital or healthcare facility, patients and staff are exposed to electrical currents, which have the potential to be fatal. Leakage current can pass through the human body either directly through the skin (this is known as macro shock) or through devices, supplies or equipment, such as pacemakers or catheters (this is known as micro shock). Electric shocks can be particularly hazardous for patients who are undergoing treatment in hospital, as they are likely to be more vulnerable.
Medical power supplies are regulated using strict limits, which are considerably lower than equipment and devices used for non-medical purposes. This is to offer enhanced protection for patients and staff who are exposed to currents through the use of specialist medical equipment and devices.
Equipment that is intended for use within the medical industry must meet guidelines set out in the safety standard IEC -1. This is an internationally-recognized safety standard, which applies to any piece of equipment, which is connected to a mains power supply and used in the observation, diagnosis, treatment or management of a patient. Examples include:
Under normal conditions, the leakage current limit for medical equipment is 10uA-500uA. This applies to a single fault condition. The table below outlines safety standards for different types of medical devices:
Leakage Current
Type B
Type BF
Type CF
NC
SFC
NC
SFC
NC
SFC
Earth Leakage current
500uA
1mA
500uA
1mA
500uA
1mA
Enclosure Leakage current
100uA
Hengfeng Product Page
500uA
100uA
500uA
100uA
500uA
Patient Leakage current
100uA
500uA
100uA
500uA
10uA
50uA
NC= Normal Conditions SFC= Single Fault Conditions
FSP specializes in low leakage medical power supplies, providing equipment, which meets international safety standards and certifications. FSPs medical power supplies include PC medical power supply, medical power supply adapter, open frame power supply and backup power for medical applications. With decades of experience in supplying clients with high-quality products and services, FSP is a leading name in the field of medical power supplies. If you have any questions, or you need advice about medical equipment, dont hesitate to get in touch.
Leakage current is current that flows from an AC or DC circuit to the ground or another conductor. If the equipment or device is not grounded correctly, it is possible for current to flow through the human body. This is why it is vital to regulate and control leakage current for medical power supplies. Safety standards help to reduce risks and keep patients and healthcare providers and support staff safe.
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Leakage current is the current that flows from either AC or DC circuit in equipment to the chassis, or to the ground, and can be either from the input or the output. If the equipment is not properly grounded, the current flow through other paths such as the human body. This may also happen if the ground is inefficient or is interrupted intentionally or unintentionally.
The leakage current in equipment flows when an unintentional electrical connection occurs between the ground and an energized part or conductor. The ground may be the reference point of zero voltage or the earth ground. Ideally, the current leaking from the power supply unit should flow through the ground connection and into the installations earth ground.
Leakage current in laptops or devices using two pin plugs is mostly through the signal cables connected to other grounded or ungrounded equipment such as printers. The other equipment provides a path to the ground if it is properly grounded or may give an electric shock to anybody touching the exposed metal parts if not properly earthed.
The leakage in devices is largely due to the imperfections in the insulators or materials that make the component such as the semiconductors and capacitors. These results into small current leaking or flowing through the through the dielectric, in the case of a capacitor.
Leakage current in power supplies may occur due to the EMC filters, which utilizes Y capacitors between the live and neutral conductors. This causes some leakage current to flow from the neutral or the live conductor to the power supply casing which is normally connected to the earth ground.
Most power supply manufacturers specify this current which should always be lower than 3.5 mA as per the IEC--1 regulations. This ensures that the current is very low and cannot harm the person who touches or comes into contact with the power supply case. A power supply with a good earth ground reduces the leakage current significantly by providing a low resistance path to the ground.
Leakage current flow in an EMC filter Image Credit
The filter manufacturers usually specify the maximum leakage current that the filter will leak, but these are only theoretical values and the actual values may deviate from these especially if parameters such as voltage or frequency change. To get an accurate value of the leakage current, it is advisable to measure the current that flows to the ground when the filter is in operation.
There are standards that specify maximum leakage currents that are safe for humans under different conditions. These vary with the application and type of possible contact as well as the type of ground connection.
Designers are supposed to ensure that the leakage current does not harm the users who touch the enclosure of a power supply or the powered equipment. All applications have their upper limit on the current that should flow. Medical equipment and other sensitive equipment are required to have very low currents due to the nature of their applications and the impact they can have.
The standards are more stringent in medical applications since the weak patients are more vulnerable to electric shocks which can be fatal.
Typical leakage current limits by an application are:
The permissible leakage current under normal conditions is 0.5mA and 1mA under a single fault condition. The leakage current is very dangerous if it exceeds the permissible safe limit. It is even worse in medical applications due to both the risk it poses to both patients and caregivers. Only a small current needs to flow through the human body to cause harm and can be fatal for patients whose immune systems are already weak. View our Medical Grade Power Supplies here.
Must have a protection against the electric shock by means of basic insulation in combination with a protective earth ground connected to the equipment case.- maximum leakage current is 0.75 mA for the handheld and 3.5mA for the other equipment.
These equipment do not have a protective earth ground. Such equipment uses reinforced or double insulation to provide protection against electric shocks. Maximum leakage current is 0.25 mA.
These are the super extra low voltage (SELV) circuits in which there are no hazardous voltages.
Leakage current will flow when it is not desired to do so, either due to poor design, failure grounding or insulation in equipment, imperfections in component materials and more. The magnitude of the current can be reduced by proper design and observing of the best standards and practices.
Different types of equipment have a permissible maximum leakage current based on application and voltage. Other than design, an effective method of reducing the leakage current is ensuring that the equipment has a proper earth ground.
All of Sunpowers products go through an extensive process of testing and have been designed to ensure that each unit not only meets all requirements, but it also developed to a higher standard than the minimum requirements. Get in touch with us today to discuss your manufacturing requirements.
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