at low voltage through the windings, or by the use of electric heaters or steam pipes. Proper temperature can be maintained during long period of idleness by placing a small heater inside the machine and covering the machine with a tarpaulin. DRYING OF WINDINGS Drying out can be most effectively accomplished by passing current through the windings. The current should be a mere fraction of full- load current,and the voltage should be low enough to be safe for the winding in its moist condition. The drying out heat may also be applied externally by the use of heating units placed around or in the machine. This method is most effective under a temporary housing of sheet metal or canvas, with a vent provided in the top for the escape of the moistureladen air. The warm air must be adequately circulated over all surfaces to be dried, and if natural draft is not sufficient to accomplish this, small fans should be used to force circulation. conveniently dried out by heating in an oven. Small machines may be Regardless of method used, the temperature should not be permitted to exceed 90°C, The time required for thorough drying out will depend to a considerable extent on the size and voltage of the machine, and on the method of heating. Insulation resistance measurements should be taken at inter- vals of several hours, until the readings become fairly constant. The normal insulation resistance value as established by AIBE Standards is as follows: Rated Voltage of Motor Megohms = Rating in KVA + 1000 100 3-35