Should the temperature of the three-phase windings of a high-voltage motor be used for alarm purposes or for interlock functions?
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As the title suggests, drawings from typical motor manufacturers will specify the alarm values and shutdown values. Is the shutdown value here the same as the interlock value? I’ve seen many pump and chemical plant manufacturers set this shutdown value to correspond to a high-alarm level; there are also pump manufacturers that use a two-out-of-three interlock system, with temperature measurements taken for each phase – but this approach isn’t very precise. Additionally, some pump manufacturers use a two-out-of-two system for single phases, which is much more reasonable. I’d like to discuss with everyone how people handle this matter – are there any industry standards, or does it entirely depend on the preferences of the project design agency?
Typically, the temperature settings for a motor’s three-phase windings are defined at two levels: an alarm value and a shutdown (interlock) value. The alarm value is used to alert operators to the equipment’s condition, while the shutdown value serves as an overheat protection mechanism for the motor; when this value is reached, the motor shuts down to prevent damage. In practical applications, different manufacturers may adjust these values according to specific requirements, such as setting high-high alarms or employing two-out-of-two interlock strategies. Industry standards may vary by region and industry; it is recommended to follow the guidelines of relevant project design institutes or industry standards for design and configuration. .
Generally, there are an alarm value and an interlock shutdown value; the machine will shut down as soon as either of these values is reached
1 With full consideration for safety, set alarms for winding temperature, and implement interlock in case of single-phase overtemperature. 2 If availability also needs to be taken into account (as shutting down the factory arbitrarily would result in heavy losses), then set up alarms, along with a two-out-of-two or three-out-of-two interlock system.