Answer / deepak g

In I.M, we generally consider the flux proportional to
torque and the slip prop. to speed in scalar control. Now
this is actually not valid for vector control. In vector
control we need to consider a dc drive analogy. i.e. the
torque is proportional to the armature current only and does
not affect flux (armature and field current which are
perpendicular to each other forming independent phasors ).So
by torque control i think it means controlling the real
component of the stator current which is formed after
resolving the stator current into quadrature and direct axis
currents.

Answer / vishok

VVVF stands for variable voltage variable frequence. These
are simple V/F drives for the steady state applications eg
fan and pump which allows a lot of time for a speed change.

Here a speed set point serves a single command for speed
change and strength of magnetic field in motor.Therefore
Separate torque control is not possible in VVVF drives. So
the torque always remains constant in VVVF drives which
equals to V/F. The voltage and frequency in VVVF drives
varry in proportion in order to maintain the torque.

Answer / hiren morkar

Scalar control is V/f control which you can use where load
behaviour is not dynamic, in scalar control u can not goes
above rated torque.the closed loop scalar control give more
precise solution.the closed loop scalar control give more
precise solution.
Vector control controling torque by seprated magnetizing
current and torque producing current, so that it can
control torque by controling flux.(magnetizing current).
It is used where load behaviour is dynamic ,the closed loop
control give more precise solution.

Answer / ajay daultani

torque vector control is nothing but control of two vector
components of stator current i.e magnetizing current Im and
rotor ( or torque ) current Ir .

Ir = Is cos( fie )
Im = Is sin ( fie )

Answer / arun

ya the above answer is correct..v/f is directly
proportional to flux .we have to maintain the flux constant
to produce constant torque..actually vector control means
tat we have to currents Idirect axis and Iquadrature
axis..Id controls the flux of the machine.Iq controls the
torque of the machine independently.

Answer / vinod

it one kind of control method in the vfd.
for example the the unwinder and rewinder has a opposite
torque directions.
in unwinder the speed and torque will be in opposite
direction
in rewinder the speed and torque will be in same direction.
so,an effective toruqr control can be made with a vvfd.

What are the reasons for AVR failure in LT DGsets ?

2 Answers  

1.What is the proper definition of power system stability? 2.some times a blue spark is visible in the secondary side of a distribution transformer at the contact position of bushings and fuse wire,why?

1 Answers  

Can a 5 core cable one end with a 32A 3p+N+E plug and the other end 32A 3p+E be used on a generator?

1 Answers  

What is the permissible value of earth resistance!

11 Answers   Torrent Power,

Can we perform parallel operation of two transformers when one transformer on load?

3 Answers  

what is raw power & normal power

2 Answers  

in a live circuit with a light bulb such that the bulb is off by a switch, is the light glows if the switch 2 terminals are both touched by a mouse?

1 Answers  

Hi frnds :) plz tell me that i have 100 KVA 3 phase generator so by thumb rule 100*1.4 = 144 amps and generaly we can operate at 80% load...so it will 144*0.8 =112 amps.... so now i m confused about single phase load.....if we use that generator only for single phase the that 112 amps is total single phase load or i can give 112 amps at red 112 amps at yellow and 112 amps at blue.... i mean that total single phase load that 100 KVA generator will take is 112+112+112=336 amp ??

2 Answers   FWO,

Can anyone tell me some hints about what type of questions are asked by the interviewer by an Electronics engineer when company is installing an IPP and wants a team of engineers?

0 Answers  

why universal motor work on ac & dc both?

1 Answers   EMC, emc2,

why do the core of transformer saturates???

1 Answers  

I WANT BHEL PREVIOUS QUESTION

0 Answers   Bhel,