VLT
®
8000 AQUA
All about VLT 8000
AQUA
■
Air humidity
VLT 8000 AQUA has been designed to meet the
IEC 68-2-3 standard, EN 50178 pkt. 9.4.2.2/DIN
40040, class E, at 40°C.
See specifications under
General technical data.
■
Efficiency
To reduce energy consumption it is very important
to optimize the efficiency of a system. The
efficiency of each single element in the system
should be as high as possible.
Efficiency of VLT 8000 AQUA (
η
VLT
)
The load on the frequency converter has little effect on
its efficiency. In general, the efficiency is the same at
the rated motor frequency f
M,N
, regardless of whether
the motor supplies 100% of the rated shaft torque
or only 75%, i.e. in case of part loads.
The efficiency declines a little when the switching
frequency is set to a value of above 4 kHz
(parameter 407
Switching frequency
).
Efficiency of the motor (
η
MOTOR
)
The efficiency of a motorconnected to the frequency
converter depends on the sine shape of the
current. In general, the efficiency is just as good
as with mains operation. The efficiency of the
motor depends on the type of motor.
In the range of 75-100% of the rated torque, the
efficiency of the motor is practically constant, both
when it is controlled by the frequency converter
and when it runs directly on mains.
In small motors, the influence from the U/f characteristic
on efficiency is marginal; however, in motors from 15
HP and up, the advantages are significant.
In general, the switching frequency does not affect
the efficiency of small motors. Motors from 15 HP
and up have their efficiency improved (1-2%). This
is because the sine shape of the motor current is
almost perfect at high switching frequency.
Efficiency of the system (
η
SYSTEM
)
To calculate the system efficiency, the efficiency
of VLT 8000 AQUA (VLT) is multiplied by the
efficiency of the motor (
η
MOTOR
):
η
SYSTEM
=
η
VLT
x
η
MOTOR
Based on the graph outlined above, it is possible to
calculate the system efficiency at different speeds.
MG.83.A2.02 - VLT is a registered Danfoss trademark
189