Difference between delta and star connection of electric motors
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Dear sea friends, I recently read an article about the delta and star connections of motors. The article stated that in the delta connection: the phase voltage equals the line voltage, and the line current is equal to square root 3 times the phase current； In star connection: line voltage = √3 times the phase voltage, line current = phase current. I’m very confused and hope that fellow sailors can help me. What are the advantages and disadvantages when changing an electric motor from delta connection to star connection?
Generally, the star connection is used for starting under reduced voltage, while the delta connection is used after starting.
This refers to three-phase asynchronous AC motors. There is a very important characteristic: when one phase of a three-phase power supply is missing for some reason, a motor connected in a delta configuration will burn out quickly, whereas a motor connected in a star configuration will not burn out, allowing enough time to cut off the power for maintenance. Low-power motors are generally connected in star configuration, while high-power motors are connected in delta configuration.
For the same motor, the power output is lower when it is connected in star configuration compared to delta connection; in other words, the shaft output power is smaller.