An isolation transformer is a transformer used to transfer electrical power from a source of alternating current (AC) power to some equipment or device while isolating the powered device from the power source, usually for safety reasons.
Medical grade isolation transformers are designed to isolate the patient and the operator from an electric shock and to protect the equipment from power surges or faulty components.For the safety of the patient in hospitals, all diagnostic or therapeutic medical equipment (medical electrical devices and non-medical electrical devices in the patient’s environment and areas for medical use) should be completely isolated from the supply line using strengthened isolation. Complete patient/operator safety is assured by medical-grade isolation transformers with very low leakage current (IEC 60601-1 medical electrical equipment).
Medical grade transformers are designed to isolate the patient and the operator from an electric shock and to protect the equipment from power surges or faulty components.Medical grade transformers also maintain strict adherence to the following:
A secure galvanic separation is provided from the public power supply, within the leakage current limits of connected devices. The low stray magnetic fields and fault-tolerant design makes these transformers suitable for use near monitors. They are not only an ideal solution for medical diagnosis or medical electronic devices, but they can also be used in IT equipment and video systems in the patient environment.
Medical grade isolation transformers use two design options to achieve isolation: safety ground, and reinforced insulation.
Safety Ground — Safety ground transformers utilize standard transformer isolation. A safety shield between the primary and secondary coils, with insulation between the shield and each coil, maintains leakage current maximums. The safety shield has to be thick to be able to meet required tests in the safety standard. If the isolation breaks, the electrical path goes directly to ground, providing safety.
Double/Reinforced Insulation — For a transformer that relies on double or reinforced insulation there is no “safety” shield, but the insulation, as indicated by the name, is much thicker. It is designed so that all layers of the insulation can pass the thickness and high potential voltage tests required by the standard. If one insulation layer breaks, the next layer will be able to provide the required safety.
In both design options, the construction design must still meet the required creepage and clearance requirements. If the transformer includes a static shield for noise reduction, it is important to note that this shield does not provide the transformer with safety ground but rather works as a functional earth. When the shield is grounded, it attenuates the common mode noise and can reduce the leakage current from the primary to the secondary winding (please note that this leakage reduction is not the same as when measured primary to ground).
Normally, without extra mechanical barriers between the primary and shield and secondary, a transformer with double/reinforced insulation has lower leakage current than the one with a safety shield.
A safety shield wire should be connected to the protective earth terminal in the equipment while the static shield, if included, should be connected to the functional earth terminal.
Medical Grade Isolation transformers are mostly used in a 1:1 ratio (the primary voltage rating equals the rated secondary voltage value). The two windings will have the same number of turns. There might be a slight difference in the number of turns to compensate for voltage drops; otherwise, the secondary voltage would be slightly less than the primary voltage.
By using isolation tape and a screen winding between the primary and secondary windings the required dielectric strength of ≥ 4 kV for reinforced and double insulation is achieved, plus the required “general earth leakage current” of < 100 µA is also achieved.
DC power supply systems such as the UPS are widely used as the source of power for modern-day IT and telecom applications. Public digital infrastructure such as IT Data Centers, mobile towers, or digital home applications such as laptops and modems rely on UPS devices for safe, uninterrupted, 24X7 DC power supply. Sometimes we may wonder why are isolation transformers used in ups systems or what is the role of an isolation transformer in UPS? Isolation transformers
play a critical role in these DC power systems as they safeguard the expensive and sensitive equipment from the irregularities of the AC mains power supply.KS Instruments
is a market leader in Isolation Transformers for Data Centers, and our products find wide application in IT Data Centers and telecom installations across the country.
The basic function of a UPS device is to ensure an “always-on” power source. It provides short-term power when the input power source fails. The on-battery run-time of most uninterruptible power sources is relatively short (only a few minutes) but sufficient to start a standby power source or properly shut down the protected equipment. It is a type of continual power system.
However, it is constantly subjected to all the “noise” from the electrical grid at the input side. If the noise reaches the main equipment, it might cause damage to the equipment, increase maintenance cost due to excessive wear and tear. It may even harm the humans who come in contact with the devices.An IT data center is the physical infrastructure that houses sophisticated computer systems and associated components, such as networking and storage devices.
Since IT operations are crucial for business continuity, it generally includes redundant or backup components and infrastructure for power supply, data communication connections, environmental controls (such as air conditioning, fire hazard control), and various security devices. A large data center is an industrial-scale operation using as much electricity as a small town
Why do we need Isolation Transformer
In earlier days, a DC power supply design included an internal transformer. These transformers would perform several protection functions as they would act as a barrier in between the primary side (the supply line) and the secondary side (connected equipment). However, adding a permanent transformer to the UPS device adds to its overall size, weight and design complexity. Here comes the role of isolation transformers for UPSNowadays, transformer-less UPS devices are more prominently used. There are basically two types of Transformer-less Power Supplies – Capacitive or Resistive. Instead of fitting the isolation transformer within the body of the UPS, it is connected externally. This enables us to install the transformer in a more optimal part of the power path, explaining the need for an isolation transformer in UPS
UPS system configuration can be done in three ways – single mains, dual mains, and single mains without bypass. These configurations are differentiated by the presence of a static bypass and how it is connected. The circuit diagrams below indicate the position of the transformer in the UPS configuration in all three types.
In the specific application of UPS usage in IT data centers, the isolation transformer installed along with the UPS supports the following critical functions