Answer / guest

There is no DC VVVF because frequency came under AC only

Answer / gangadhar

Frequency is related for only alternating current, so there
is no dc drive if you want run by the dc first convert dc
into ac after words you can use VVVF drives

Answer / nilesh m. sarate

AC vvvf drives means alternating current variable voltage
variable frequency drives its name itself indicates that
here the frequency is changing,also calld as variabl
frequency drive,converter, inverter, in which voltage
belongs to dc bus of drive & speed belongs to switchings of
IGBTs
there is only DC Drives & no Dc VVVf drve, another name is
variable speed drive, in which speed belongs to armature
voltage or field current.

Answer / gaurav

Ac drives ,or VVVF i.e variable voltage variable frequency
drive works on converting A.c into D.C through converter
(rectifier circuit),then storing the D.C voltage in dc bus
bar and through proper switching of the inverter circuit
(basically IGBTs)this D.C is converted into A.C of required
voltage and frequency,hence it saves power.
there is nothing like D.C VVVF. yes in case of D.C drive we
have to convert A.C into D.C and provide armature and field
voltage to the motor.conversion of A.c to D.C is through
SCRs as we require control dc output.

Answer / sanjeev

There is nothing like DC VVVF Drive,and AC vvvf drives
control it's output through it variable frequency,we can't
check the voltage at motor with multimeter,and IGBT for
speed reference does two works,speed and during stop or
braking the regenrated voltage thrown to it's incoming
itself hence saves power.

Answer / s.balamurugan

If frequency increase speed will increase, If frequency
decrease speed will decrease. so when the frequency is
zero, there is no speed(rotation).that means there is no Ac
voltage.so this voltage like dc (because there is no
frequency).

Answer / arfa

VVVF is a frequency converter for ac motor speed cotrol but
I dont hear "dc VVVF" .

Answer / rawat

In AC VVVF drive we control the motor by changing its
frequency through drive. But in case of Dc drive there is
armature voltage and field voltage which are controlled by
scr's.
So there is no frequeny in case of dc drive as here dc is
not changing into ac.

Answer / edgar segovia

In DC current we have no frequency so instead of VVVF
drives we use CONVERTERS (rectifiers) and control
armature, field currents and voltages to get motor speed
control. In AC we use VVVF drives which means VARIABLE
VOLTAGE AND VARIABLE FREQUENCY, i.e. we have to control
both frequency and voltage to avoid SLIP thus not losing
torque. With a CONVERTER we go from AC to DC and then to
power electronics to get motor control through the above
mentioned parameters. With a VVVF drive we go a little bit
further since we first go from AC to DC, then we pass
through a FILTERING device and then go to the real
inverter which goes from filtered DC back to AC (nowadays
by meas of PWM). Forgot to mention in AC drives we also
have external resistors to absorve regenerative power (IGBT
controlled as well), in this way we avoid lines pollution
as well (harmonics).

Answer / tapiwanashe vhurumuku

vvvf stands for variable voltage variable frequency .this can only be used when first changing direct current into alternating current

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