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VLT 8000 AQUA (Legacy Product)

Danfoss VLT 8000 AQUA (Legacy Product), VLT® in Oilpump User guide

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VLT
®
in Oil Pump Applications
MN.90.B1.02 - VLT is a registered Danfoss trademark
This application note contains a description of the
use of VLTs in an oil pump application at the oil
company YPF in Argentina. Figure 1 is a drawing of
this application.
Figure 1
When installing a similar application please note
that:
- The VLT 6000 Series cannot be used in this
application, because it does not feature the
required functions.
- In order to prevent that the transformer is
saturated during start up, the VLT must not start
at 0 Hz.
■■
■■
■ VLTs in Oil Pump Applications
VLT in Oil Pump Applications
Oil pump application
M
3,5 kV
230 kW
Cable lengh: 2-3 km
Transformer
VLT
VLT
®
in Oil Pump Applications
MN.90.B1.02 - VLT is a registered Danfoss trademark
Figure 2, the VLT U/f-ratio
Figure 2, see the frequencies between f
a
and f
b
. (f
start
> 0 Hz).
In the application at YPF in Argentina, f
start
was set
to 5 Hz (VLT 5000: parm. 130 and f
min
at stop parm.
123).
- If a good transformer with low iron losses is used,
the LC-filter might not be necessary. It is the
current harmonics which may cause thermal
problems in the transformer.
When a poorer transformer is used, an LC-filter is
required.
It must therefore be checked that the harmonics do
not disturb or cause problems in the transformer.
This is done in the following way:
- Go through the whole motor frequency range on
the VLT when no motors or secondary motor
cables are connected.
- Look at the current in the display to the
transformer. It must not suddenly increase and
be less than 2-3 % of the motors nominal
current (I
N
).
- Turn OFF the overmodulation (VLT
®
5000: par.
413).
- Check the rotors direction of rotation.
Figure 3, illustrates how to check if the direction of
rotation is correct.
VLT in Oil Pump Applications
U
f [Hz]
5 Hz
U(mains)
U/f-ratio
f(start)
The transformer is not linear
The
p
um
p
s VT-characteristic
I [A]
f[Hz]
I[b]
Wrong direction
I[a]
Direction OK when I[a] > I[b]
You check the current level at a frequency!
Right
Wrong
VLT
®
in Oil Pump Applications
!
MN.90.B1.02 - VLT is a registered Danfoss trademark
- When selecting the right VLT for the
application, remember that there is a current
loss in the transformer. The loss can be
approx. 2-3 %.
- Submerged pumps are cooled by the
surrounding media flow. Therefore, at YPF, the
minimum pump frequency, f
min
in parm. 201,
had to be set to a speed at which the oil was
just coming out of the oil pipe.
- At YPF, restarting the pump was only allowed
after 20 minutes. This was done with an
external timer.
NB!
Check if there are similar limitations in your
pump application.
If the ON-delay is less than 10 minutes, relay 01
on the VLT control card can be used. The Relay
01 ON-delay can be programmed in parm. 324.
Relay 01 can then be connected to terminal 18
or 27 and the chosen terminal should then be
programmed to STOP. In this way the VLT will
not restart before the R01 ON-delay time has
expired.
- The transformer will have taped voltage outputs
terminals. They can be used to eliminate voltage
drops caused by the cable and thereby ensuring
the right voltage on the motor terminals. This is
done in successive steps on the transformer.
The fine adjustment can be done with the VLT
output voltage. The VLT output frequency is set
to the motor nominal frequency.
Figure 4, illustrates how to find the right motor
voltage.
The right motor voltage is found by adjusting the
transformer voltage and then reading the VLT
current output. At the lowest value you have the
right voltage.
VLT in Oil Pump Applications
I [A]
U[V]
At nominal motor
frequency
VLT in
p
ut volta
g
e
/