Transformer safety

An isolation transformer is a Isolation transformers block transmission of the DC component in signals from one circuit to the other, but allow AC components in signals to pass. Transformers that have a ratio of 1 to 1 between the primary and secondary windings are often used to protect secondary circuits and individuals from electrical shocks between energized conductors and earth ground. Suitably designed isolation transformers block interference caused by Some specifications require that Isolation transformers be a part of the lightning protection on the AC circuits. Terminology [ ] Sometimes the term is used to emphasize that a device is not an primary purpose is to isolate circuits are routinely described as isolation transformers. Operation [ ] Isolation transformers are designed with attention to Applications [ ] Pulse transformers [ ] Some small transformers are used for isolation in Electronics testing [ ] In electronics testing and servicing, an isolation transformer is a 1:1 (under load) power transformer used for safety. Without it, exposed live metal in a Electrical isolation is considered to be particularly important on medical equipment, and special standards apply. Often the system must additionally be designed so that fault conditions do not interrupt power, but generate a warning. Supply of equipment at elevated potentials [ ] Isolation transformers are also used for the power supply of devices not at ground potential. An example is the See also [ ] • • •...

Courtesy of Based on the 2020 NEC. Article 450 of the National Electrical Code (NEC) opens by saying, “This article covers the installation of all transformers.” Then it lists eight exceptions. So, what does it really cover? Essentially, this Article covers transformers supplying power and lighting loads. For the purposes of Art. 450 only, a transformer is an individual power transformer (single- or 3-phase,)identified by a single nameplate — unless otherwise indicated. A major concern with transformers is preventing overheating. The Code does not completely address this issue. Article 90 explains that the NEC is not a design manual, and it assumes that anyone using the Code has a certain level of expertise. Proper transformer selection is an important part of preventing transformers from overheating. The NEC assumes you have already selected a transformer suitable for the load characteristics. Article 450 then takes you to the next logical step — providing overcurrent protection and the proper connections. But it does not stop there; Sec. 450.9 provides ventilation requirements, and Sec. 450.13 contains accessibility requirements. Part I contains the general requirements (such as guarding, marking, and accessibility), and Part II contains requirements for specific types of transformers. Overcurrent protection for transformers not over 1,000V Transformers having a secondary voltage not exceeding 1,000V, with primary overcurrent protection only, must have the primary overcu...

Pad-mounted transformers are part of the underground electrical system. They are placed on easements or right-of-ways in yards and serve the same purpose as transformers on utility poles. Because transformers may serve several homes, underground lines may go out from them in many directions. Guidelines to remember when planting near transformers: • Maintain a 4-foot clearance to the sides and back of the transformer. Equipment inside the box generates heat and needs air circulation to keep cool and run efficiently. Overheating could case an outage. • Maintain a 10-foot clearance in front of the transformer. Equipment inside is energized at high voltage. Line crews work on “energized” transformers to avoid interrupting your service. The linemen use long insulating sticks and need the clear space to work safely. • Use gravel, wood chips, grass, or low ground cover around the transformer. Flowers are okay but may get trampled if we have to work on it. • Never dig beside a transformer or install fences or storage buildings near them. Crews need clear access 24 hours a day to safely perform the necessary maintenance or restore power. • Under Minnesota law, you must call

As the use of electrical medical equipment expands, from hospitals and hospices to home-based monitoring and life support, so too has concern over operator and patient safety. While there are stringent design rules based on good design practice and multiple safety standards to prevent dangerous or even lethal shock from the line voltage, it can still happen. All it takes is for a fault in the instrument to cause its enclosure or external probes to become “live,” placing the user or patient in a fault-current path to ground. With a properly selected and placed transformer, this can be avoided. Transformers of course have many uses, from stepping alternating current (AC) voltages up or down or breaking ground loops of sensitive transducer interfaces, to impedance matching, interstage coupling, and implementing transformations between single-ended and balanced circuits. They are also used at a 1:1 turns ratio to provide galvanic isolation between the AC line and a load. This last function is increasingly important and relevant in the context of protecting operators and patients from medical equipment design faults. This article will look at the nature of the possible fault modes and the use of a transformer for AC line isolation and thus, safety in line-powered medical instruments. Using representative units from How do electrical shocks happen? To understand the shock risk, it is useful to return to the first principles of electricity. The user is at risk if current, driven ...