Danfoss VLT Micro Drive PK18 Design Manual page 17

Safety and Conformity
2.5.7 Star/Delta Starter or Soft-starter not
Required
2 2
When larger motors are started, it is necessary in many
countries to use equipment that limits the start-up current.
In more traditional systems, a star/delta starter or soft-
starter is widely used. Such motor starters are not required
if a frequency converter is used.
As illustrated in the illustration below, a frequency
converter does not consume more than rated current.
800
700
600
500
400
300
200
100
0
0
2.5.9 Without a Frequency Converter
D.D.C.
V.A.V.
Sensor P
Table 2.1 Fan System made in the Traditional Way
16
VLT Micro Drive Design Guide
4
3
2
1
12,5 25 37,5 50Hz
Full load
& speed
= Direct Digital Control
= Variable Air Volume
= Pressure
MG02K102 - VLT
®
1.
VLT Micro Drive FC 51
2. Star/delta starter
3. Soft-starter
4. Start directly on mains
2.5.8 Using a Frequency Converter Saves
Money
The example on the following page shows that a lot of
equipment is not required when a frequency converter is
used. It is possible to calculate the cost of installing the
two different systems. In the example on the following
page, the two systems can be established at roughly the
same price.
E.M.S. =
Sensor T =
®
is a registered Danfoss trademark
Energy Management system
Temperature