![]() ![]() Figure 3 shows an evaluation board that uses one of RECOM’s SMD DC/DC converters to provide isolated bus power. This is one of the reasons why isolated CAN-bus systems are often used in heavy industrial automation plants and production processes. Any electrical interference is ignored by the differential bus topology, without the danger of external fields inducing an overall current flow in the wiring. As both ends of the bus are isolated, the transmitter and receiver can sit at different ground potentials without problem. The CAN-bus specification does not specify that the bus wiring must be isolated, but in practice, isolating the interface eliminates many potential sources of error or interference with the data transmission. The isolation provides added security against interference or increases reliability, but is not safety-related.Ī good example is a CAN-bus data communication system. In these applications, an isolation fault would not cause injury or serious damage to the equipment, or often even stop the application from working. Typical applications for functional isolation converters include non-safety-critical systems, where the isolation is primarily used to break ground loops, block conducted interference paths or to provide a change in functional ground reference voltage. This method has the advantage of being low cost and yielding a very compact-sized transformer which, despite the small size, can withstand up to 4kV DC isolation voltage testing, but with limited duration and as a non-repetitive test.įigure 2: Ring core transformer with functional isolation So how do these classes translate into practical transformer construction?įor functional isolation, transformer primary and secondary windings are typically wound directly over one another, relying on the thickness of the wire lacquer for insulation (Figure 2). Reinforced – a single barrier equivalent to two layers of Basic insulation.Supplementary - an additional barrier to basic, required by agencies for redundancy.Basic - the isolation offers shock protection as long as the barrier is intact.Functional - the output is isolated, but there is no protection against electric shock.For DC/DC converters, the most commonly used classes are: The isolation grade is dependent on the robustness of the isolation barrier. Modules with defective module isolation, unshielded wires, defective power optimizers, or an inverter internal fault can cause DC current leakage to ground. ![]() for multiple functional circuits.ĭataforth's MAQ ®20 and I/O modules all feature power supply Isolation.Figure 1: Some different ways of using an isolated DC/DC converter Then isolated DC to DC converters make the final low voltage DC such as 1.8, 3.3, 5.0, etc. ![]() Power main voltages are usually reduced and rectified to DC voltages less than 60VDC. Thus power supplies in consumer, industrial, military, and communications systems almost always have isolated supplies. Such a circulating current may cause galvanic corrosion of wiring eventually causing failure of one or multiple circuits. Since wires are never perfect short circuits at DC and certainly not at high frequency AC, unwanted voltages are excited in each circuit. Isolation prevents ground loops that occur when different circuits share the same ground.Ĭurrent may then circulate in the ground of an interconnected circuit. These can be expensive and need protection from power main spikes. In modern systems, the supply load is often delicate, low voltage devices such as microprocessors and associated storage and signal conditioning circuits. These refer to DC voltages below 60VDC, and are deemed be safe for human contact. Low voltage is defined as Safety Extra Low Voltage (SELV) and Functional Extra Low Voltage (FELV). Low voltage DC to DC converters, in many cases, need electrical isolation from input to output. ![]()
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