Why Submersible Motors Fail – Part 2

In this issue of Franklin AID we will continue to review “Why Submersible Motors Fail”. However, before we do, in the September/October issue on CHECK VALVES, we spoke of a “soft start” in reference to water hammer. Someone asked, “What is a soft start?” A “soft start” is another term commonly used to describe a reduced voltage starter.

Voltage Surges and Spikes:

High voltage surges and voltage spikes are the result of close proximity lightning strikes, opening of power line switch gear, fast current-limiting power line switch gear, or the removal of large inductive loads from the power lines. These spikes and surges can travel to the motor windings, where they attempt to break down the insulation resistance. While Franklin motors can handle voltage surges in the magnitude of 10,000 volts, unfortunately, power surges do not limit themselves to this voltage. This is why a good surge arrestor, capable of multiple hits, is needed for submersible motors without internal arrestors (4-inch single-phase motors have built-in arrestors). Remember, there is little advantage to installing an arrestor unless it is grounded to the water strata. Surge arrestors over the years have also been known as lightning arrestors. While a direct lightning strike of millions of volts to the motor is almost impossible to protect against, voltage surge related motor failures can be prevented with good arrestors and proper grounding. Continue reading