【Daily Question 20090203】Can a self-enclosed transformer be used as a safety light transformer?
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Can an autotransformer be used as a transformer for safety lighting? Why? Summary: It’s not allowed because there is still an electrical connection between the primary and secondary sides of a self-enclosed transformer, which prevents proper safety isolation; this can lead to electric shock and ground short circuits during use. This post was last edited by lihy on 2009-2-4 17:39.]
From a security perspective, it is not allowed. A safety lamp transformer is a transformer with a primary coil and a secondary coil that are isolated from each other. The principle is the same as that of a transformer, based on electromagnetic induction; it primarily isolates the primary power circuit, leaving the secondary circuit floating with respect to ground, thereby ensuring electrical safety. The voltage of the ungrounded secondary side is also low. So, people won’t get an electric shock when in contact with the secondary side. An autotransformer is a special type of transformer that shares the same set of coils for input and output, with different taps being used to step up or step down voltage. Part of the winding is shared by the high-voltage side and the low-voltage side, while another part belongs only to the high-voltage side.
It seems it shouldn’t be possible; as for why, I asked an expert for an explanation.
An autotransformer is a special type of transformer in which the output and input share the same set of coils. Voltage stepping up and stepping down is achieved using different taps; fewer taps than those shared by the coils result in a lower voltage, while more taps lead to a higher voltage. A safety lamp transformer is a transformer with a primary coil and a secondary coil that are isolated from each other. The principle is the same as that of a transformer, based on electromagnetic induction; it primarily isolates the primary power circuit, leaving the secondary circuit floating with respect to ground, thereby ensuring electrical safety. The voltage of the ungrounded secondary side is also low. So, people won’t get an electric shock when in contact with the secondary side. Therefore, they cannot be substituted for each other!
It is absolutely not allowed. As a specific power supply for safe voltage, the safety light transformer must ensure that under normal and fault conditions, the effective value of the AC voltage (50HZ-500HZ) between any two conductors or between any one conductor and ground does not exceed 50V. The input circuit and output circuit of the transformer must be strictly electrically isolated, and the secondary circuit is not allowed to be grounded. To prevent high voltage from leaking into low voltage, the core of the transformer (or isolation layer) should be firmly grounded or connected to neutral. Autotransformers cannot be used as a source for safe voltage.
The enclosure of the street light transformer must be properly grounded; autotransformers shall not be used.
An isolation transformer, as the name suggests, serves primarily to separate electrical devices from the power grid. It is used in situations where safety is a concern or where interference suppression is necessary; there is no direct electrical connection between the electrical devices and the power source. An autotransformer, on the other hand, has its secondary side that forms part of its primary side, similar to a three-terminal adjustable resistor. There is a direct electrical connection between the output and input of such a transformer, and it is generally used for adjusting the voltage of equipment.
It’s definitely not possible; self-enclosed transformers use a single set of coils for both high and low voltage, which is far from safe. Moreover, the most important aspect of a safety light transformer is its safety features
No, the advantage of an autotransformer is that it can be used not only for stepping down voltage; by simply swapping the input and output sides, it can function as a step-up transformer. Of course, what the original poster suggested is not acceptable. Autotransformers are not permitted to be used as safety isolation transformers due to their shortcomings: if the phase wire and the neutral wire are connected in reverse at the input side, the output voltage on the secondary side remains unchanged and the device can still function normally, but in this case the \"neutral\" wire carries a high voltage, which is extremely dangerous.
No! A safety lamp transformer is a transformer with a primary coil and a secondary coil that are isolated from each other. The primary power circuit is mainly isolated, while the secondary circuit remains floating with respect to ground, in order to ensure electrical safety; moreover, the voltage of the ungrounded secondary side is low. The term \"coupling\" in autotransformers refers to electromagnetic coupling. Ordinary transformers transfer energy through electromagnetic coupling between their primary and secondary coils, with no direct electrical connection between them. In an autotransformer, however, there is a direct electrical connection between the primary and secondary coils; the low-voltage coil is actually part of the high-voltage coil. In current power grids, autotransformers become available starting from the 220 KV voltage level, and are mostly used as inter-grid connection transformers. There are hardly any autotransformers below 220KV. An autotransformer is one in which a portion of its windings is shared by both the high-voltage side and the low-voltage side, while another portion belongs only to the high-voltage side.