VLT
®
2800 Series
In both cases, the reduction is carried out
linearly, down to 60% of I
VLT,N
.
■
Vibration and shock
The frequency converter has been tested according to
a procedure based on the following standards:
IEC 68-2-6: Vibration (sinusoidal) - 1970.
IEC 68-2-34: Random vibration broad-band
- general requirements.
IEC 68-2-35: Random vibration broad-band
- high reproducibility.
IEC 68-2-36: Random vibration broad-band
- medium reproducibility.
The frequency converter complies with requirements
that correspond to conditions when the unit is mounted
on the walls and floors of production premises, as
well as in panels bolted to walls or floors.
■
Air humidity
The frequency converter has been designed to
meet the IEC 68-2-3 standard, EN 50178 item
9.4.2.2/ DIN 40040 class E at 40 °C.
■
UL Standard
This device is UL-approved.
■
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 frequency converters (
η
INV
)
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% rated shaft torque
or only 75%, e.g. in case of part loads.
This also means that the efficiency of the frequency
converter does not change even if other U/f
characteristics are chosen. However, the U/f
characteristics influence the efficiency of the motor.
The efficiency declines a little when the switching
frequency is set to a value above 4.5 kHz (parameter
411
Switching frequency
). The rate of efficiency will
also be slightly reduced at a high mains voltage (480
V), or if the motor cable is longer than 25 m.
Efficiency of the motor (
η
MOTOR
)
The efficiency of a motor connected to the
frequency converter depends on the sine shape
of the current. In general, the efficiency is just as
good as in mains operation. The efficiency of the
motor depends on the motor type.
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 general, the switching frequency does not affect
the efficiency of small motors.
Efficiency of the system (
η
SYSTEM
)
To calculate the system efficiency, the efficiency of
the frequency converters (
η
INV
) should be multiplied
by the efficiency of the motor (
η
MOTOR
):
η
SYSTEM
=
η
INV
x
η
MOTOR
.
Based on the graph above, it is possible to calculate
the system efficiency at different loads.
MG.28.E9.02 - VLT is a registered Danfoss trademark
134
