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Inrush current VS. Surge current

At Innoraymond we use the terms "inrush current" and "surge current" to refer to the electrical current happenings at power-up of an electric motor. When comparing inrush current and surge current, we are talking about two very different things. 

Inrush current; typically occurs during the first ~150 milliseconds after a device is switched on, also referred to as LRA or "locked rotor amps." Depending on the device, inrush current can reach levels exceeding 500% of the devices current rating. For example, a 15 amp motor can see inrush current levels of 75 amps RMS! Depending on the application, these levels of inrush current are unnecessary, non-beneficial, damaging, and should be eliminated.

Surge current; occurs during the 0-3 seconds following inrush current, and will vary greatly depending upon the type of equipment and its design. Surge current is the result of an increased current demand by the motor in order to get to its steady-state level. Our goal is to keep surge current levels to a minimum, without sacrificing the torque requirements of some systems, in a time-conscious manner.


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