4
VLT
®
3500 HVAC
MG.35.B1.02 – VLT is a registered Danfoss trademark
Principle of the VLT 3500 HVAC
A frequency converter rectifies AC voltage from the
mains supply into DC, and then modifies this into a
variable AC voltage with variable amplitude and
frequency.
■
1. Mains supply
3
×
200 / 220 / 230 V A.C., 50 / 60 Hz
3
×
380 / 400 / 415 V A.C., 50 / 60 Hz
3
×
440 / 460 / 500 V A.C., 50 / 60 Hz.
2. Rectifier
A three-phase rectifier bridge which rectifies AC
into DC.
3. Intermediate circuit
Direct current = 2 x mains voltage [V].
4. Intermediate circuit coils
Even out intermediate circuit voltage and reduce
mains supply interference from harmonic currents.
5. Intermediate circuit capacitor
Evens out the intermediate circuit voltage.
6. Inverter
Transforms DC voltage into variable AC voltage
with variable frequency.
1.3 Principle of the VL
T 3500 HV
AC
The motor is thus supplied with variable voltage and
frequency, which enables infinitely variable speed
regulation of three-phase, asynchronous standard
motors.
Selection of options and accessories
Danfoss offers a wide range of options and accessories
for the VLT 3500 HVAC. For additional information please
contact Danfoss.
■
7. Motor coils
Advantages of motor coils:
•
Long motor cables can be used.
•
100% protection against earthing and
short-circuiting.
•
Unlimited number of switchings on the
frequency converter output.
8. Motor voltage
Variable AC current, 10-100% of the supply
voltage.
Variable frequency: 0.5-120 Hz.
By regulating voltage and frequency (U/f
characteristics) into a given ratio, the con-
nected motor is enabled to supply the desired va-
riable torque (VT) to the pump or fan.
9. Control card
This is where the computer is found that controls
the inverter which generates the pulse pattern by
which the DC voltage is transformed into variable
AC voltage with variable frequency.
NB!:
In order to obtain satisfactory operation of the
frequency converter it is highly important to select
the necessary options and accessories.
