Specifications
CAUTION
Connection to PC is carried out via a standard host/
device USB cable.
The USB connection is galvanically isolated from the
supply voltage (PELV) and other high-voltage terminals.
The USB connection is
not galvanically isolated from
protection earth. Use only an isolated laptop/PC as
connection to the USB connector on the frequency
converter or an isolated USB cable/converter.
8.2 Efficiency
Efficiency of the Frequency Converter ( 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
, even if the motor supplies
100% of the rated shaft torque or only 75%.
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 slightly when the switching
frequency is set to a value of above 5 kHz. The efficiency is
also slightly reduced if the mains voltage is 480 V, or if the
motor cable is longer than 30 m.
Frequency converter efficiency calculation
Calculate the efficiency of the frequency converter at
different loads based on Illustration 8.2. The factor in this
graph must be multiplied with the specific efficiency factor
listed in the specification tables:
1.0
0.99
0.98
0.97
0.96
0.95
0.93
0.92
0% 50%100% 200%
0.94
Relative Eciency
130BB252.11
1.01
150%
% Speed
100% load 75% load 50% load 25% load
Illustration 8.2 Typical Efficiency Curves
Example: Assume a 55 kW, 380-480 V AC frequency
converter at 25% load at 50% speed. The graph shows
0.97. Rated efficiency for a 55 kW FC is 0.98. The actual
efficiency is then: 0.97x0.98=0.95.
Motor Efficiency (
η
MOTOR
)
The efficiency of a motor connected to the frequency
converter depends on magnetizing level. 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 11 kW
and up, the advantages are significant.
In general, the switching frequency does not affect the
efficiency of small motors. Motors from 11 kW up have
their efficiency improved (1-2%) 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 the
frequency converter (η
VLT
) is multiplied by the efficiency of
the motor (η
MOTOR
):
η
SYSTEM
= η
VLT
x η
MOTOR
8.3 Acoustic Noise
The acoustic noise from the frequency converter comes
from three sources
1. DC intermediate circuit coils.
2. Integral fan.
3. RFI filter choke.
The typical values measured at a distance of 1 m from the
unit:
Frame size dBA at full fan speed
N90k 71
N110 71
N132 72
N160 74
N200 75
N250 73
E1/E2-Frames
1)
74
E1/E2-Frames
2)
83
F-Frames 80
Table 8.9 Acoustic Noise
1)
315 kW, 380-480 V AC. 450 and 500 kW, 525-690 V AC only.
2)
All other E-frame Units
General Specifications and ... VLT® HVAC Drive FC 102 Design Guide
194 MG16C102 - Rev. 2013-08-20
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