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Locked Rotor Current Formula:
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Locked Rotor Current (ILR) is the current drawn by an electric motor when its rotor is locked and unable to rotate. This represents the maximum current the motor will draw during startup and is typically 6 times the Full Load Amps (FLA).
The calculator uses the Locked Rotor Current formula:
Where:
Explanation: The formula provides an approximate calculation of the starting current for electric motors, which is typically 6 times the normal operating current.
Details: Calculating locked rotor current is essential for proper circuit breaker and overload protection sizing, voltage drop calculations during motor startup, and ensuring electrical systems can handle motor starting currents.
Tips: Enter the motor's Full Load Amps (FLA) value in Amps. This value is typically found on the motor nameplate or in manufacturer specifications.
Q1: Is the 6x multiplier always accurate?
A: While 6x is a standard approximation, actual locked rotor current can vary between 5-8 times FLA depending on motor design and type.
Q2: Why is locked rotor current important?
A: It helps determine the proper sizing of circuit protection devices and ensures the electrical system can handle the initial surge current during motor startup.
Q3: How long does locked rotor current last?
A: Typically only for a brief moment during startup (a few seconds) until the motor reaches operating speed.
Q4: Can locked rotor current damage motors?
A: If the motor remains in locked rotor condition for too long, it can overheat and cause damage. Proper overload protection is essential.
Q5: Are there different multipliers for different motor types?
A: Yes, some specialized motors may have different locked rotor current multipliers. Always consult manufacturer specifications for precise values.