Answer / neha a patel

The Induction motor can be stopped immediately by just
interchanging any two of the stator leads. When an
induction motor is rotating at a high speed, during
emergency if situation arises that the motor has to be
stopped immediately, can be done by interchanging any 2
leads of the stator supply. By doing this, it reverses the
direction of the revolving flux, which produces a torque in
the reverse direction, thus causing a breaking effect on
the rotor. This breaking period is called the “Plugging”
period

Answer / sunil guru

PLUGGING ----- can be applied only for 3 ph. induction motor.
in this phenomenon motor running at full speed can be stopped (braking)by reversing the polarity of any 2 ph. out of any 3 ph.(R,Y,B).......
so that the rotating magnetic field is produced in opposite direction thus the torque produced act in opposite to the previous motion and the motor can be stopped......
but the disadvantage is that when the motor attains the zero speed the phase should be again interchanged to protect the motor from moving in opposite direction (extra provisions should be made for that.......)

for any disagreement mail me at parmar20072008@yahoo.com

Answer / preetee

Plugging consists in a reversal of phase sequence of the supply voltage,

which is easily accomplished by interchanging any two supply leads of the motor. This results in reverse rotation of the magnetic field in the motor; the slip becomes greater than unity and the developed torque tries to force the motor to rotate in the opposite direction. If only stopping of the drive is required, the motor should be disconnected from the power line at about the instant of zero speed.
Plugging is quite a harsh operation, because both the kinetic energy of the drive and input electric energy must be dissipated in the motor, mostly in the rotor. This braking method can be compared to shifting a transmission into reverse to slow down a running car. The total heat produced in the rotor is approximately three times the initial energy of the drive system. Therefore, plugging must be employed with caution to
avoid thermal damage to the rotor. Low-inertia drives and motors with high rotor resistance and, therefore, with a large high-slip torque (see Figure 2.17) are the best candidates for effective plugging.
which is only two-thirds of the rated torque, while the stator current is 6.6 times the rated value. The maximum braking torque using this method occurs at zero speed and equals the starting torque

if installing the transformer why put the sprit the stone ?

1 Answers  

---

what is the difference b/w winding insulation class and winding temperature class?

6 Answers   Bhel, NDPL, NTPC,

---

Why neutral grounding Transformer provided for generator?

1 Answers   Siemens,

---

what is extra low voltage system

3 Answers  

---

WHAT TYPES OF OIL(STRUCTURE) ARE USED IN POWER TRANSFORMER INSULATION?

4 Answers  

---

why delta delta connection generally not use in transformer

4 Answers   Lanco,

---

Instead of single phase(220), if we apply Phase to phase (R&Y)supply (eg: for lighting fixture). what will be the power formula?

1 Answers  

---

if we apply 1000ADC instead of 100ADC or We apply 50ADC instead of 100ADC,What will be happened in the test result value.Pl explain

0 Answers   NCC,

---

why ct ratio always rated 5.

1 Answers  

---

Which element has power dissipated in it when the source is removed ?

2 Answers   SSC,

---

why the neutral of power transformer is always earthed?

1 Answers  

---

If load is 240 kw & pf is 0.8 lagging, than how to increase it from0.8 to 1.0(unit),which rating capacitor used, please give me Calculation. What is effact of consumer & suplier if pf is lagging or leading with on effect machines/ TF/GE etc.

6 Answers   L&T,

---