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Series C:
Voltage Drop Calculation

As most motors are designed to operate with a 5% voltage drop, divide volts lost by line voltage to determine if a larger conductor or additional feed points are required.


Determining Amperage: - The national electric code suggests loads:
  1. For one motor, use 100% of motor nameplate full load ampere rating.

  2. For multiple motors on a single crane or hoist, the minimum circuit ampacity of the power supply conductors on a crane or hoist shall be the nameplate full load ampere rating of the largest motor or group of motors for any single crane motion, plus 50% of the nameplate full load ampere rating of the next largest motor or group of motors.

  3. For multiple cranes and/or hoists supplied by a common conductor system, compute the motor minimum ampacity for each crane as in step (2), add them together and multiply the sum by the demand factor from the following table:

    Number of cranes 2 3 4 5 6 7
    Demand factor .95 .91 .87 .84 >.81 .78


  4. For constant loads such as magnets, lights and air conditioners, etc., plus high duty cycles, use full load amperage, in selecting conductor size.