MG.20.B6.02 – VLT is a registered Danfoss trademark
25
VLT
®
2000 Series
Section 1
Section 2
Section 3
How the VL
T works
Control accuracy
Basically we distinguish between open loop and
closed loop control.When the control is an open loop
type the motor current acts as process feedback. The
final result is therefore highly dependent on the
characteristics of the motor.
Note that large motors give a better result than small
motors.
Open loop (depending on motor size)
±
2.0 %
3-100 Hz (10-90% of max. torque)
PI (closed loop)
±
0.5%
1.2-100 Hz (-90 - +90% of max. torque)
A closed loop control incorporates a direct process
feedback, which substantially improves the control
accuracy.
The stated maximum torque follows the power hyper-
bola in the frequency range across the motor’s rated
frequency.
Galvanic isolation
With the VLT 2000 Series safety isolation is standard,
as the high-voltage parts of the power section are
galvanically isolated from the low-voltage parts of the
control section according to VDE 0160/0106 (PELV).
Therefore PCs and the like will not be disturbed.
Advanced motor protection
The VLT 2000 Series has a built-in electronic thermal
motor protection. The frequency converter calculates
the motor temperature on the basis of voltage,
current, frequency and time.
The thermal motor protection is comparable with a
thermal relay in the motor cables. Therefore it is
superior to the traditional bi-metallic protection, where
the altered cooling conditions due to the speed
control are not taken into consideration.
Long motor cables
For the VLT 2000 Series motor coils in an IP 00 or IP
10 enclosure are available as modules.
This makes it possible to install a long cable between
motor and frequency converter.
Motor coils are also included in the RFI and motor
filter module in IP 20 enclosure. See page 34 for a
speciffication of maximum cable length.
Programmable control inputs and
signal outputs in 2 setups
The digital technique used in the VLT 2000 Series
makes it possible to redefine the different control
inputs and signal outputs and to program 2 different
user defined setups.
It is easy for the user to program the required
functions on the keyboard of the VLT 2000 Series or
via the RS 232 user interface.
Protection against mains disturbance
The VLT 2000 Series is protected against transients
arising on the mains, e.g. when you switch in power
factor phase-correction capacitors or when the
supply is subject to lightning strikes.
Adequate motor voltage and full torque can be main-
tained down to 10% under-voltage on the supply
mains.
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