Low temperature/high humidity failure modes of a DC electric motor

The results of a study on DC electric motors operated in a low-temperature/high-humidity test environment are described. Above a certain threshold temperature the start-up current characteristic remains well within design parameters. As the temperature drops below a certain threshold the start-up current increases slightly in amplitude but, more significantly, the duration of the current pulse increases. After protracted start-stop cycling at temperatures below threshold the current pulse width may extend for up to 30 seconds and the motor may stall during start-up. Typical start-up current profiles are presented over a range of operating conditions. For low temperature/high humidity extremes several distinguishing features may be noted in these profiles. These results will allow other researchers and design engineers to determine if similar patterns of behaviour are likely to arise in other DC motor systems which are operated at extremes of temperature and humidity.