Getting motors through the monsoon

Every year from late June, our breakdown desk gets a run of calls about motors that tripped on a wet morning. Pune’s monsoon brings heavy rain, high humidity and flooded pump pits, and electric motors do not like any of it. A little preparation in May and June prevents most of these failures.

Before the rains, walk round every motor that sits outdoors or in a pit. Check that terminal box covers are closed and their gaskets intact, that cable glands are tight and that drain plugs at the bottom of the motor are clear. Motors in pits need the pit drain or sump pump working. A simple sheet-metal canopy over an outdoor motor helps, as long as air can still move around it for cooling.

Measure insulation resistance with a megger on motors that stand idle for weeks, such as standby pumps and seasonal equipment. Record the reading. A healthy low-voltage motor usually reads well above 100 megohms; a reading that is dropping month by month warns of moisture before a failure.

If a motor has been wet or the reading is low, do not simply switch it on. Dry it first, with its anti-condensation heater if fitted, or in our oven, where a slow bake at around 80 °C for 12 to 24 hours usually brings the reading back. For motors that stand idle through the monsoon, run them for 15 minutes once a week, so the heat drives out moisture. Our monsoon check visit for a plant of up to 40 motors costs ₹6,500.