Enter the machine, drive, duty and site to get the induction motor size, operating load, starting time and current and the voltage dip on the supply.
Pre-sizing and estimating tool: results do not replace design, calculations or reports signed by a licensed professional, nor verification against the applicable codes and standards.
The area between the curves is the torque that accelerates the drive. If the curves touch, the motor does not reach rated speed.
Motor speed (left axis) and current as a multiple of rated (right axis).
Motor shaft power in each step and the RMS power used for selection.
Take this page’s results to another calculator with the fields already filled in.
The report gathers this page's inputs, results, equations, assumptions and references, with fields for project, engineer and revision. In the print dialog, choose Save as PDF.
Calculate machine shaft power, divide by drive efficiency, apply the margin and altitude and temperature derating, and pick the next standard NEMA rating. Then check that starting torque overcomes the load and that acceleration time is acceptable.
Below about 50% load, efficiency and especially power factor drop, while starting current and cost rise. A well-chosen motor runs between 75 and 100% of rated power.
Star-delta and soft starters reduce starting current but also torque, so they suit pumps and fans. For loads that start with high torque or need variable speed, a VFD is the choice.
Important notice: Indus Metrics tools produce estimates and pre-sizing results from the data you enter and from published engineering methods. They do not replace design, calculations or reports signed by a licensed professional engineer (PE), nor verification against the applicable codes, standards and regulations, such as OSHA rules and the ASME codes. Material and fuel properties vary: check manufacturer data or your own process analyses before deciding. By using this site you agree to the Terms of Use.
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