10.11 Eciency
Eciency of the drive (η
VLT
)
The load on the drive has little eect on its eciency. In
general, the eciency is the same at the rated motor
frequency f
M,N
, whether the motor supplies 100% of the
rated shaft torque or only 75%, in case of part loads.
The eciency of the drive does not change even if other
U/f characteristics are selected. However, the U/f character-
istics inuence the eciency of the motor.
The eciency declines slightly when the switching
frequency is set to a value of above 5 kHz. The eciency is
slightly reduced when the mains voltage is 480 V, or if the
motor cable is longer than 30 m (98 ft).
Drive eîš…ciency calculation
Calculate the eciency of the drive at dierent speeds and
loads based on Figure 10.16. The factor in this graph must
be multiplied with the specic eciency factor listed in the
specication tables in chapter 7.1 Electrical Data, 380–480 V
and chapter 7.2 Electrical Data, 525–690 V .
1.0
0.99
0.98
0.97
0.96
0.95
0.93
0.92
0% 50% 100% 200%
0.94
Relative Eciency
130BB252.11
1.01
150%
% Speed
100% load 75% load 50% load 25% load
Figure 10.16 Typical Eîš…ciency Curves
Example: Assume a 160 kW, 380–480 V AC drive at 25%
load at 50% speed. Figure 10.16 shows 0.97 - rated
eciency for a 160 kW drive is 0.98. The actual eciency is
then: 0.97x 0.98=0.95.
Eciency of the motor (η
MOTOR)
The eciency of a motor connected to the drive depends
on magnetizing level. In general, the eciency is as good
as with mains operation. The eciency of the motor
depends on the type of motor.
In the range of 75–100% of the rated torque, the eciency
of the motor is practically constant, both when the drive
controls it and when it runs directly on the mains.
In small motors, the inuence from the U/f characteristic
on eciency is marginal. However, in motors from 11 kW
(14.75 hp) and up, the advantages are signicant.
Typically the switching frequency does not aîš„ect the
eciency of small motors. Motors from 11 kW (14.75 hp)
and up have their eciency improved (1–2%) because the
shape of the motor current sine-wave is almost perfect at
high switching frequency.
Eciency of the system (η
SYSTEM
)
To calculate system eciency, the eciency of the drive
(η
VLT
) is multiplied by the eciency of the motor (η
MOTOR
):
η
SYSTEM
=η
VLT
x η
MOTOR
10.12 Acoustic Noise
The acoustic noise from the drive comes from 3 sources:
•
DC intermediate circuit coils.
•
Internal fans.
•
RFI
lter choke.
Table 10.24 lists the typical acoustic noise values measured
at a distance of 1 m (9 ft) from the unit.
Enclosure size dBA at full fan speed
D1h/D3h/D5h/D6h 73
D2h/D4h/D7h/D8h 75
E1h–E4h 80
Table 10.24 Acoustic Noise
Test results performed according to ISO 3744 for audible
noise magnitude in a controlled environment. Noise tone
has been
quantied for engineering data record of
hardware performance per ISO 1996-2 Annex D.
A new fan control algorithm for E1h-E4h enlosure sizes
helps improve audible noise performance by allowing the
operator to select diîš„erent fan operation modes based on
specic conditions. For more information, see
parameter 30-50 Heat Sink Fan Mode.
Electrical Installation Con...
VLT
®
AQUA Drive FC 202
172 Danfoss A/S © 01/2018 All rights reserved. MG22B222
1010
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