Answer / pinias munyongani j

VFD is used to vary the speed of the motor through varying
frequency. Where as a soft starter is used to smoothly
start up a motor. How ever VFDs can also achive smooth
start ups if the ramp up and ramp down times are increased.
Probably the main reason for using the soft starter is that
the cost is relatively lower than that of a VFD.

Answer / rajnish

according to me soft starter is only to reduce the kick
current for safety of motor and to its connected parts.
where as in VFD we can not only control the speed of motor
but can control the starting speed ( acceleration) and
stopping speed(deacceleration)of motor.

Answer / dikesh patel

we are using soft starter ofallen bradely flex model for
180 kw hall screw motor configuration of s s is in delta
mode i always observer the starting kick around 9oo amp flc
of motor is 180 amp how soft starter is not limiting its
starting current up to 400/500 amp it is almost about the
stardelta kick then how we can say that soft starter is
meant for limiting starting current kick

Answer / naresh singh thakur engineer e

vfd means variable frequency it it is used where speed
variation is required it saves the energy also for example
we use vfd in air compressor when compressor is in load
mode motor runs at full speed & while compressor is in
unload mode the motor runs at its reduced speed up to 30 %
of full speed hence at this time energy saved.
we can achieve the speed above the rated speed & below the
rated speed using vfd the basic is the formula
NS = 120 * F / P
where ns = speed of motor
120 angle in electrical degree between two windings or coils
F = frequency which is to be varied
p= Number of poles
wher if no of poles = 2 fix
120 degree is fix
f= 0 to 70 above
put these values in formula & find results

while soft starters are the earlier version of vfd with
some less features than vfd

Answer / electrical work

Soft starter is used to start motor smoothly by limiting current for that used thyristors to control its voltage. Its change voltage to acquire smoothness of current and torque. Selection of soft starter depend on number of starting, application and motor power. once motor gets its speed, soft starter bypass motor to contactor and monitors the motor current current. When stop is required again soft starter take controlling of motor and stop motor. Both acceleration and deceleration can be set by soft starter. It used where soft stars is required and then motor is running in full speed.
VSD is used V/F controlling method and it gives soft start and current and controlling is done by changing drive output frequency. VSD is used where Variable speed required.

Answer / mahmoud sawalhi

VFD : The drive consists primarily of two parts, one
which converts AC (50 or 60 Hz) to DC and the
second part which converts the DC back to AC,
but now with a variable frequency of 0-250 Hz.In many
applications a drive is still used for starting and
stopping the motor and for speed regulation
during a normal run .

softstarter: A softstarter has different characteristics
to the other starting methods ,It has thyristors in the
main circuit, and the motor voltage is regulated
with a printed circuit board ( but the frwquency cannot be
cotrolled like in VFD ).

Answer / anup patil

The Starting current of motor is very high.To protect the
motor from the high starting current we use soft
starters.VFD's on the other hand are also called as
Variable Speed Drives where we can change the speed of the
motor from 0rpm to motor rated rpm by varying the
frequency.It is mainly used to operate the motor at its
variable speed.By use of soft starters the motor reaches at
its full load smoothly and after reaching at its full speed
it acts as a VFD.

Answer / thamprasad

Values for various popular resistance thermometers
Values for various popular resistance thermometers
Temperature
in °C Pt100
in Ω Pt1000
in Ω PTC
in Ω NTC
in Ω NTC
in Ω NTC
in Ω NTC
in Ω NTC
in Ω
Typ: 404 Typ: 501 Typ: 201 Typ: 101 Typ: 102 Typ: 103 Typ:
104 Typ: 105
−50 80,31 803,1 1032
−45 82,29 822,9 1084
−40 84,27 842,7 1135 50475
−35 86,25 862,5 1191 36405
−30 88,22 882,2 1246 26550
−25 90,19 901,9 1306 26083 19560
−20 92,16 921,6 1366 19414 14560
−15 94,12 941,2 1430 14596 10943
−10 96,09 960,9 1493 11066 8299
−5 98,04 980,4 1561 31389 8466
0 100,00 1000,0 1628 23868 6536
5 101,95 1019,5 1700 18299 5078
10 103,90 1039,0 1771 14130 3986
15 105,85 1058,5 1847 10998
20 107,79 1077,9 1922 8618
25 109,73 1097,3 2000 6800 15000
30 111,67 1116,7 2080 5401 11933
35 113,61 1136,1 2162 4317 9522
40 115,54 1155,4 2244 3471 7657
45 117,47 1174,7 2330 6194
50 119,40 1194,0 2415 5039
55 121,32 1213,2 2505 4299 27475
60 123,24 1232,4 2595 3756 22590
65 125,16 1251,6 2689 18668
70 127,07 1270,7 2782 15052
75 128,98 1289,8 2880 12932
80 130,89 1308,9 2977 10837
85 132,80 1328,0 3079 9121
90 134,70 1347,0 3180 7708
95 136,60 1366,0 3285 6539
100 138,50 1385,0 3390
105 140,39 1403,9 vfd are used where intially the low
torque is needed and stator initiall torque must be high

Answer / anil

VFD USED TO GET VARIABLE SPEED REQUIRED AND TORQUE
APPLICATION BUT SOFT STARTER AS SAME AS STARTER WHICH
DIRECTLY FIX IN RACK THAT COMMUNICATE PLC

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