Oil Filled Transformer Frequently-Asked Questions

Click on question marks below to get answers to these frequently-asked questions.

Why doesn’t the oil in an electrical transformer burn?

There is not an electrical arc inside an oil filled power transformer and the oil in a power transformer does not get hot enough to burn. Most oil filled transformers are sealed. The oil may burn if the oil filled transformer fails and there is an electrical arc inside the power transformer and it is powerful enough and lasts long enough to rupture the transformer tank and cause the oil to spill and then burn. This does not happen very often.

Why is oil used in an electrical transformer?

Oil is actually a great electrical insulator for the wire windings and iron core of a power transformer. It also is a coolant to carry the heat away from the electrical transformer windings and iron core to the cooling radiators on the side of the oil filled transformer. The heat is created by the flow of electrical current through the wire windings that are used to make a power transformer.

Why don’t oil filled transformer manufacturers fill power transformers with something that does not burn?

Actually they do. Some electrical power transformers are filled with nonflammable fluid such as liquid silicone or “less flammable” fluids such as Rtemp or other high fire point hydrocarbons (ie Fire point of at least 300 0 C). But these fluids are much more expensive than mineral oil, therefore manufacturers only use them when required by code or specification such as when the electrical transformer is going to be placed inside a building.

In terms of quality and efficiency, are most power transformers about the same?

No, they are not. There are huge differences in the reliability and efficiency of electrical transformers. Power transformers are often purchased based on minimum electrical and physical criteria. Unfortunately this can be very short sighted. MIDWEST Engineers are frequently asked to perform an “Engineering Analysis” of the most appropriate transformer for a customer’s total needs. The analysis can be very complex. It considers reliability, efficiency, voltage anomalies, through faults, the present value of the lifetime cost of the transformer and many other factors. Purchasing the wrong power transformer could cost ten of thousands of dollars of unnecessary expense over the years and could result in hundreds of thousands of dollars of production losses due to unexpected failure.

If I wanted to learn more about electrical power transformers, what other search terms would I use?

Used, Reconditioned, Surplus, and New

GE; General Electric; Square D transformers are a few of the many sold by MIDWEST; Popular low voltage distribution units by Eaton; Cutler Hammer; The old Sorgel and Allis Chalmers; ITE; MIDWEST features new Jefferson Transformers; MGM; Hammond; Westinghouse; Hevi Duty; Other name mfg are ACME; Federal Pacific; And some unknown transformer mfg.

OIL FILLED POWER TRANSFORMERS MANUFACTURERS

Used, Surplus, Reconditioned, Rewound, Remanufactured, and New

GE; General Electric; Westinghouse; RTE are a few transformers supplied by MIDWEST. GEC Alsthom; Square D; Wagner; Cooper Power Systems are featured in MIDWEST’s inventory; We also have refurbished Allis Chalmers; Ferranti Packard; Line Material; Foundries will recognize McGraw Edison; Pennsylvania; Magnetek; MIDWEST is proud to provide ITE; Standard; Federal Pacific: Vantran.