. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . To Starting Box111,. 6. ( IMPI IUND MOTOR. three phase alternating current. Thismotor consists of two parts, the statoror stationary part, also called the field,and the rotor or rotating part some-times called the armature. The statorhas coils of wire placed symmetricallyaround the inside of the frame in slots,and these coils are connected to the elec-tric power supply. The rotor also hascoils in slots, but there are no connec-tions to the power circuit. The principle of the induction motor M
. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . To Starting Box111,. 6. ( IMPI IUND MOTOR. three phase alternating current. Thismotor consists of two parts, the statoror stationary part, also called the field,and the rotor or rotating part some-times called the armature. The statorhas coils of wire placed symmetricallyaround the inside of the frame in slots,and these coils are connected to the elec-tric power supply. The rotor also hascoils in slots, but there are no connec-tions to the power circuit. The principle of the induction motor March, 1911. RAILWAY AND LOCOMOTIVE ENGINEERING 125 depends on Lenzs Law, which in sub-stance is as follow?: If a magnet or fieldis passed by near a coil of wire there isinduced in this coil a current which exertsa drag on the magnet or field tending topull the same back. It is this inducedcurrent which makes the motor work,hence the name induction motor. Al-though the windings around the frame. To Starting Box FIG. 7. INTERPOLE MOTOR. of the stator are equally distributed me-chanically, they are grouped electricallyinto a certain number of sets, accordingto the number of poles of the 8 shows the scheme of connectionsfor the stator of a four-pole, three-phaseinduction motor, and there are aroundthe stator twelve groups, each consistingof six coils; one group for each pole pereach phase. Alternating current does not give aconstant force like direct current, butchanges in value. Starting at zerovalue it reaches a maximum, then de-creases to zero again, and reversesto the maximum and back to zero, all ina fraction of a second. This changefrom zero back to zero is called a cycle,and a twenty-five cycle current is onein which there are twenty-five of thesecycles per second. It is similar to a loco-motive where the steam first pushes thecrosshead, then pulls it with varyingforce and which is zero at points ofreversal or ends of the strokes. In a three-phase circuit the
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