Variable transformer Variac

Many forms and sizes of magnetic stirring apparatus are available commercially. These include those fitted with an electric hot plate attached to the flat top the hot plate is controlled by an energy regulator or variable transformer (Variac). 

The mixture may be heated by means of a steam or water bath, but in view of the long reflux period it is better to use a hemispherical electric heating mantle controlled by a variable transformer (Variac). 

Turn on the variable transformer (Variac or Powerstat) and adjust it to about 1/3 of a full setting (80 on a 240 scale). 

Turn on the variable transformer (Variac) (A) and apply about 15 volts (check with your instructor for the proper setting to obtain 50 °C). 

Adjust the variable transformer (Variac or Powerstat) to 40 volts. 

The submitters used a transformer purchased from the Franklin Transformer Company, Minneapolis, Minnesota, for 25-30. It was provided with taps so that secondary voltages of 5500, 6600, 7700, 8800, 9900, and 11,000 could be obtained. These transformers do not always deliver the rated voltage and hence should be calibrated by actual measurement. The checkers used a luminous tube transformer obtained from the Jefferson Electric Company, Bellwood, Illinois, Cat. No. 721-411. Cap. 825 VA. Primary 115 V.A.C. 60 cycles. Secondary 15,000 V. 60 M.A. Price 19.60. The variable transformer used to regulate the voltage should be rated at 7.5 amperes and may be a Varitran, Adjustavolt, or Variac. 

Figure 1 is a schematic diagram of the system used in this study. The system pressure was controlled with a Cartesian Manostat 6A (Mano-stat Corporation) and a Welch mechanical pump Model 1402 (W. M. Welch Manufacturing Company). The discharge was initiated and sustained with a 7,000/12,000 volt Jefferson luminous tube outdoor-type transformer (Jefferson Electric Company) connected to a 60-c.p.s. 110-volt power source through a Variac variable transformer. 

The temperature of the bubbler, the cell, and the associated gas lines, was controlled by wrapping each with heating tape and controlling the power input with a Variac variable transformer. The system was maintained at or below atmospheric pressure for this study, with most of the data being obtained at 2 to 3 in. of mercury below atmospheric pressure (2 to 3 in. of mercury vacuum). 

A variable transformer (trade names Variac and Powerstat) is a device for changing the voltage applied to the heating wires in the heating mantle. 

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