MG.20.B6.02 – VLT is a registered Danfoss trademark
53
VLT
®
2000 Series
Section 1 Section 2 Section 3
The control possibilities of the VLT
Load and motor (group 1..) (continued)
Closed loop control - PI controller:
If closed loop control is required, the transmitter,
tacho-meter or encoder should supply one of the
analogue standard signals (e.g. 0-10 V, 0-20 mA, 4-
20 mA) or a pulse signal frequency of max. 100 Hz, 1
kHz or 10 kHz (programmable).
The reference signal can either be fixed internally (di-
gital reference) or be a standard analogue signal or
pulse signal.
Control with closed loop
The feedback value should be 50-80% of the reference
signal. It is not possible to select the same type of signal
(voltage, current, pulse) for both the reference and the
feedback.
At start the ouptut frequency is determined by the
reference and the feed forward factor (parameter 119)
and the f
MAX
and f
MIN
settings of the frequency converter.
When a feedback signal is registered, the PI controller
then corrects the ouptut frequency by comparing with
the reference/feedback signals.
At stop the output (integrator) is set to 0 so that a
restart follows the normal start situation.
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