RESISTANCES.
The type of resistance now most common for heavy motor equipment is in the form of cast-iron grids, which are assembled together and connected in series. These grids are sufficiently stiff to render unnecessary any solid insulation between them, and hence they can radiate heat to the best advantage. The only difficulty experienced with them is from the warping or cracking. Resistances for lighter equipment are composed of sheet-steel ribbons wound in coils. Each turn of a coil is insulated from the next by asbestos. Other forms of sheet-steel resistance with asbestos insulation between the turns, have also been used. In [Fig. 32] is shown a Westinghouse grid type diverter for street railway equipment.