Efficiency; Acoustic Noise - Danfoss VLT AQUA Drive FC 202 Design Manual

Selection
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 isolated laptop/PC as connection
to the USB connector on the frequency converter or an
isolated USB cable/converter.

3.2 Efficiency

Efficiency of the frequency converter (η
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 , even if the motor supplies
M,N
100% of the rated shaft torque or only 75%, in case of part
loads.
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
slightly reduced when 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 speeds and loads based on Illustration 3.2. The
factor in this graph must be multiplied with the specific
efficiency factor listed in the specification tables in
3.1.1 Mains Supply 3x380-480 V AC and 3.1.2 Mains Supply
3x525-690 V AC.
1.01
1.0
0.99
0.98
0.97
0.96
0.95
0.94
0.93
0.92
0% 50%
% Speed
100% load 75% load
Illustration 3.2 Typical Efficiency Curves
Example: Assume a 160 kW, 380–480 V AC frequency
converter at 25% load at 50% speed. Illustration 3.2 shows
0.97 - rated efficiency for a 160 kW frequency converter is
0.98. The actual efficiency is then: 0.97x 0.98=0.95.
®
VLT AQUA Drive FC 202 Design Guide
)
VLT
100% 150% 200%
50% load 25% load
®
MG20Z102 - VLT is a registered Danfoss trademark
Efficiency of the motor (η
MOTOR)
The efficiency of a motor connected to the frequency
converter depends on magnetizing level. In general, the
efficiency is 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 the
frequency converter controls it 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 and up have
their efficiency improved (1–2%) because the shape of the
motor current sine wave 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 ) is multiplied by the efficiency of
VLT
the motor (η ):
MOTOR
η x η
=η
SYSTEM VLT MOTOR

3.3 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:
Enclosure
N110
N132
N160
N200
N250
N315
E1/E2 *
E1/E2 **
F1/F2/F3/F4
F8/F9/F10/F11/F12/F13
* 315 kW, 380–480 VAC. 450 kW and 500 kW, 525–690 V
AC only.
** Remaining E1+E2 power sizes.
Table 3.9 Acoustic Noise Levels
)
Full fan speed [dBA]
71
71
72
74
75
73
74
83
80
84.5
51
3 3