Answer / rajesh

In any process plant or factory , we need motor to move /
compress / pump/blow/ventilate etc . in motors we have dc ,
ac , synchronous motors . dc motor are not as efficient as
ac 3 phase motor , hence we use ac motor .

now a 3 ph ac motor has nonlinear speed /torque
characteristics u can see in any website . this means that
for any torque desired speed is not constant .to achieve
this we have to keep supply voltage to frequncy constant .
this is done by vfd . as such variation of suply voltage is
impossible hence we vary frequency .
3 types 1.pwm 2. direct control etc

Answer / faiyaz ahmad

VFD-vfd stand for variable frequency drive-its controller which is used to control the motor turbine and cooler fan in the process industries its control the speed of motor and cooler fan it can increase the speed and decrease the speed of motor.

What are the two states of a controller

3 Answers  

---

List three types Level Gauges with their working principles

0 Answers   ABB,

---

dear sir we have insatlled positioner model no.sipart PS2 make Siemens at our control valves . now problem is if we want to increase the response of valve opening speedy /fast. what parameters do we change for positioner ? any idea. please guide us.

0 Answers   CPL,

---

what different types of problems do occur while doing instrumentation commisioning and how to solve them? please explain in detail

0 Answers   Process Control Technologies,

---

What is zener diode? What is voltage regulator?

0 Answers  

---

Difine flashing , Cavitaion & Noise? how to minimize these effects

3 Answers   L&T,

---

What is eddy current? Describe the operating principle of proximity probe.

0 Answers  

---

What is impulse line size

3 Answers   IFFCO,

---

what is skin thermocouple?

3 Answers  

---

What is a PID controller and how can it to applied to our everyday life?

4 Answers  

---

why orfice is not used for main steam flow calculation

0 Answers   OEG,

---

please send me hpcl placement papers

13 Answers   HPCL, L&T,

---