Double cage rotor

This is another way of obtaining improved starting performance without affecting its running performance. Though it is more expensive it gives better performance than deep bar rotor construction. The stator of double cage rotor induction motor is same as that ordinary induction motor. Rotor consists of two cages or two layers of bars short circuited … Continue reading Double cage rotor

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Deep bar Rotor

There is no constructional difference between stator of seep bar rotor motor and that of ordinary induction motor. The rotor consists of deep bars, short circuited by two end rings one on each side. The magnetic leakage flux lines are shown by dotted lines. Now consider that the bar consists of many number of layers … Continue reading Deep bar Rotor

High torque Cage Machines

In case of slip - ring induction motor an external resistance can be added in the rotor circuit during starting which gives higher starting torque and lower starting line current at an improved power factor. This resistance is then gradually cut from the rotor circuit which would otherwise result in decrease of full load speed, … Continue reading High torque Cage Machines

Constant V/f speed control

We have seen the Stator Frequency control. In stator frequency control ⇒ Two things gets changed different as to Constant V/f speed control. (i). Here maximum torque remains unaltered (As ratio of V/f = Constant) (ii). Magnetic condition of machines also gets unaltered. (Φm = K V1 / f) In case of Only stator frequency control : In case … Continue reading Constant V/f speed control

Speed Control of Induction Machines

We have seen the Derivation for Torque expression in earlier post Torque Expression for Induction Motor. T = KT s α / (s2 + α2) Here KT is Torque constant = 3 E21 / ωs X’2 And α is the machine constant = R’2 / X’2 At running condition : α = 0.1 and s = 0.06 / 0.07 Means ⇒ α2 >> s2 T ≈ KT s / … Continue reading Speed Control of Induction Machines

Theory of Induction machines with varying flux (Φ)

As we have discussed earlier the Equivalent circuit of an Induction machine Equivalent circuit of Induction Machine. Here Rotor rectance has become independent of speed (N) or Slip (s). But Rotor resistance has become a function of speed or Slip. Illusion : Never forget that the Rotor rectance is the function of Slip. Analysis of Induction … Continue reading Theory of Induction machines with varying flux (Φ)

Starting of Slip-Ring Induction motors

It is known that in slip ring induction motor, externally resistance can be added in the rotor. Let us see the effect of change in rotor resistance on the torque produced. We know that torque produced by an induction motor is given by T = KT s α / (s2 + α2) Where KT is torque constant = 3 … Continue reading Starting of Slip-Ring Induction motors