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Inrush current, input surge current, or switch-on surge is the maximal instantaneous input current drawn by an electrical device when first turned on. Alternating-current electric motors and transformers may draw several times their normal full-load current when first energized, for a few cycles of the input waveform.
NEMA (National Electrical Manufacturers Association) contactors and motor starters are rated by sizes. These sizes are grouped by rated current and power . [ 1 ] [ 2 ]
A motor soft starter is a device used with AC electrical motors to temporarily reduce the load and torque in the powertrain and electric current surge of the motor during start-up. This reduces the mechanical stress on the motor and shaft, as well as the electrodynamic stresses on the attached power cables and electrical distribution network ...
Now, if this motor is fed with current of 2 A and assuming that back-EMF is exactly 2 V, it is rotating at 7200 rpm and the mechanical power is 4 W, and the force on rotor is = N or 0.0053 N. The torque on shaft is 0.0053 N⋅m at 2 A because of the assumed radius of the rotor (exactly 1 m).
Constant air-gap induction motor equivalent circuit The circle diagram (also known as Heyland diagram or Heyland circle ) is the graphical representation of the performance of the electrical machine [ 1 ] [ 2 ] [ 3 ] drawn in terms of the locus of the machine's input voltage and current. [ 4 ]
Fleming's left-hand rule. Fleming's left-hand rule for electric motors is one of a pair of visual mnemonics, the other being Fleming's right-hand rule for generators. [1] [2] [3] They were originated by John Ambrose Fleming, in the late 19th century, as a simple way of working out the direction of motion in an electric motor, or the direction of electric current in an electric generator.
During the start-up a typical rotor has 3 poles connected to the slip ring. Each pole is wired in series with a variable power resistor. When the motor reaches full speed the rotor poles are switched to short circuit. During start-up the resistors reduce the field strength at the stator. As a result, the inrush current is reduced. Another ...
At 30 degrees the amplitude of the motor currents supplied by the autotransformer are only half the peak motor current that occurs at 90 degrees.(sine30° = 0.5) see Figure 8. The central switch therefore prevents any step-up autotransformer connection and a practicable means of controlling the switching transient to a lower value than the star ...