Answer / vipul jain

In the case starter, the capacitors are often controlled by
the main contactor which is also controlling the motor.
This is because the capacitance and the inductance of the
motor form a resonant circuit. While the motor is connected
to the supply, there is no problem. Once the motor is
disconnected from the supply, it begins to decelerate. As it
decelerates, it generates voltage at the frequency at which
it is rotating. If the capacitive reactance equals the
inductive reactance, i.e. unity power factor, we have
resonance. If the motor is critically corrected (pf = 1) or
over corrected, then as the motor slows, the voltage it is
generating will pass through the resonant frequency set up
between the motor and the capacitors. If this happens, major
problems can occur. There will be very high voltages
developed across the motor terminals and capacitors causing
insulation damage, high resonant currents can flow, and
transient torque's generated can cause mechanical equipment
failure.

Answer / g.v.hema chandu

The unity power factor means the angle b/w voltage and current is unity.As a practical it is not possible for motors because motor is inductive.For an theory if motor is at unit power factor the speed decreases.

give me name of current and volatge control device

1 Answers  

---

Why need 3phase machine double earthing?

0 Answers  

---

why the emf of a cell more than the terminal voltage when the cell is delivering current?

4 Answers  

---

HELLO SIR, IAM PREPARING HPCL EXAMS. SO PLS SEND MATERIAL OF HPCL ELECTRICAL ENG..TO VIJAY_8888@YMAIL.COM

0 Answers   HPCL,

---

In Round type three phase transformer why the LV side is inner part and HV outer part in the design of transformer? why they cant be opposite?

2 Answers  

---

Sir,In our company there are 3 caterpillar make(capacity:(1) 3.3KV,2.5MW(2)3.3KV,2.5MW & (3)3.3KV,1.9MW) & 1 deutz make (capacity:11KV,3.8MW)gas engines utilised,all are running in paralell. There are three transformer utilised,(1) 6.25MVA,3.3KV/22KV,Impedence voltage:6.7% used for two generator,both are 2.5MW(2)5.5MVA,3.3KV/22KV,Impedence voltage:7.2% used for one generator of 2.5MW & (3) 5.5MVA,11KV/22KV,Impedence voltage:7.8% used for one generator of 2.5MW.all generator breakers capacity of 1250Amps. Sir,I want the details of fault level calculation of generator,transformer individually & for whole system. If you require any information from me.feel free for contact me sir.pl.send the answer of my question as the earliest as possible.

0 Answers   Piramal Healthcare,

---

in ACB breaker requireding 3200Amps. buscoupler getting OFF mode and again it reset and getting normal position give me a required answer?

0 Answers  

---

how can i determine the gear ratio for a rack and pinion system if an electronic gate operated by an electric motor is to travel a distance of 5meters in 15 seconds.

0 Answers  

---

For DG set,if the loading is increased,does flue gas temperature increases or not?

2 Answers   NTPC,

---

what is the higest transmission voltage and generated voltage in india

14 Answers  

---

sir i have applied for isro-09. still i did not got the HALL TICKET.

2 Answers  

---

What happens when reactive power enters a system?

6 Answers  

---