i have read different forums explaining what really is an isolation transformer but unfortunately i am having trouble on grasping the main idea? please help, why do they say that isolation transformer can help a person being electrocuted even if he touches one of the secondary terminals??? how is that??? thank you
AC line voltage has one wire (neutral) grounded and the other hot. Touching the hot lead is dangerous, as your body can have a path to ground via various means. The isolation transformer removes that grounded neutral connection, so touching the hot lead on the output of that transformer is not dangerous as there is no path for the current to flow in. You have to make contact with both of the two leads to be a hazard, to provide a current path.
you know, transformer passes AC only not DC. Isolation means here is the isolation from the mains AC out let. Once the mains input voltage is not there in the primary, there will not be any secondary voltage as well. Hence one will not be electrocuted once the primary winding is being disconnected from the mains.Hence you are isolated from live and neutral of the mains outlet.One still gets electrocuted, when touched in secondary terminal provided that the primary terminals are connected to the mains input.Only the difference is that he/she is not contact with the the mains input voltage(Outlet) of having live and neutral terminals.Now, briefly saying, you are isolated from the Live and neutral terminal of the mains outlet and hence you are not direct in contact with the live and neutral terminals which may cause the current circulation(Close circuit) from live to neutral via load or ie your body(if you touch the only even one live wire or faulty neutral) and then get electrocuted. Now in case of secondary terminals, if one touches one of the secondaries(Be ware of the High voltages and have Safety First) there is no neutral to get the closed circuit and wont get electrocuted.). But oe still will get electrocuted if the path is leaky. Again safety First.Thank you.
An isolating transformer is any transformer with a double winding. That is it isolates the secondary from the primary galvanically. It would normally have an earthed interface.The primary will normally have one phase earthed at the main supply transformer. It simply creates a separate distribution system. It is basically for use on equipment that uses a chassis for a return path, but the equipment would be double insulated to protect the user from electric shock. If having an earthed phase is so dangerous, why do electricity company's have one? On ships, we did not have an earthed neutral, we generated 440 volt 3 phase. No neutal. The lighting was via 440- 230, 3 phase transformers still no neutral, earthed or otherwise. When legislation came in regarding use of power tools having to be max 55v to earth, we had to purchase 230/110 volt safety isolating transfomers and earth the centre tap of the transfomer to provide max 55 volt max fault voltage, phase to earth. Earth being the hull of the ship. Earthing is a very complicated subject. Rules and regulations regarding earthing change constantley. In the UK anyway. Try the site below.
how does isolation transformer prevent a person from being electrocuted when touched the secondary? There are two common ways to get electrocuted by line powered equipment. Using an isolation transformer eliminates one of those ways. To get electrocuted electric current has to flow across your body, typically your heart. If you connect each of your hands to the output leads of an isolation transformer, you still get electrocuted. But there is another way to get electrocuted using line powered equipment. One side of the electric outlet is tied to earth ground, so if you touch something connected to the hot side of the wiring and have something else (like your other hand) connected to something that is grounded (like plumbing or a grounded appliance) you get electrocuted. The output of an isolation transformer floats the output in relation to earth ground, so if you touch some part of the transformer's output very little current will flow through you even if you are standing in water. You may wonder why I said very little current instead of zero current. The reason is that we live in an imperfect world where the insulation in the transformer may not be perfect and your body has a tiny bit of capacitance. For most purposes this doesn't matter but if you are dealing with medical equipment with electrodes attached near the heart, this sort of thing has to be addressed. A GFI outlet works in a somewhat related way. It compares the electric current in the hot and neutral lines in the socket. If these currents don't match, the assumption is that something is shorting the hot side to ground (maybe through you!) and cuts the power.
