Control Principle - Danfoss VLT 7000 Series Manual

Control principle

A frequency converter rectifies AC voltage from
mains into DC voltage, after which this DC
voltage is converted into a AC current with a
variable amplitude and frequency.
1. Mains voltage
3 x 380 - 460 V AC, 50 / 60 Hz.
2. Rectifier
A three-phase rectifier bridge that rectifies AC
current into DC current.
3. Intermediate circuit
DC voltage = 1.35 x mains voltage [V].
4. Intermediate circuit coils
Even out the intermediate circuit voltage and reduce
the harmonic current feedback to the mains supply.
5. Intermediate circuit capacitors
8
VLT® 7000 Booster
The motor is thus supplied with variable voltage and
frequency, which enables infinitely variable speed
control of three-phased, standard AC motors.
Even out the intermediate circuit voltage.
6. Inverter
Converts DC voltage into variable AC voltage
with a variable frequency.
7. Motor voltage
Variable AC voltage, 0-100% of mains supply voltage.
8. Control card
This is where to find the computer that controls
the inverter which generates the pulse pattern by
which the DC voltage is converted into variable
AC voltage with a variable frequency.
MG.70.A1.02 - VLT is a registered Danfoss trademark