Acoustic Noise; Du/Dt Conditions - Danfoss VLT AQUA Drive FC 202 Design Manual

Electrical Installation Con...
Example: Assume a 160 kW, 380–480 V AC drive at 25%
load at 50% speed. Illustration 10.15 shows 0.97 - rated
efficiency for a 160 kW drive is 0.98. The actual efficiency is
then: 0.97x 0.98=0.95.
Efficiency of the motor (η
MOTOR)
The efficiency of a motor connected to the drive 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 drive
controls it and when it runs directly on the mains.
In small motors, the influence from the U/f characteristic
on efficiency is marginal. However, in motors from 11 kW
(14.75 hp) and up, the advantages are significant.
Typically the switching frequency does not affect the
efficiency of small motors. Motors from 11 kW (14.75 hp)
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 system efficiency, the efficiency of the drive
(η ) is multiplied by the efficiency of the motor (η
VLT
η x η
=η
SYSTEM VLT MOTOR

10.12 Acoustic Noise

The acoustic noise from the drive comes from 3 sources:
•
DC intermediate circuit coils.
•
Internal fans.
•
RFI filter choke.
Table 10.15 lists the typical acoustic noise values measured
at a distance of 1 m (9 ft) from the unit.
Enclosure size
E1h–E4h
Table 10.15 Acoustic Noise
Test results performed according to ISO 3744 for audible
noise magnitude in a controlled environment. Noise tone
has been quantified 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 different fan operation modes based on
specific conditions. For more information, see
parameter 30-50 Heat Sink Fan Mode.
MG22B102
Design Guide
)
):
MOTOR
dBA at full fan speed
80
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10.13 dU/dt Conditions

NOTICE
To avoid the premature aging of motors that are not
designed to be used with drives, such as those motors
without phase insulation paper or other insulation
reinforcement, Danfoss strongly recommends a dU/dt
filter or a sine-wave filter fitted on the output of the
drive. For further information about dU/dt and sine-wave
filters, see the Output Filters Design Guide.
When a transistor in the inverter bridge switches, the
voltage across the motor increases by a dU/dt ratio
depending on:
•
The motor cable (type, cross-section, length
shielded or unshielded).
•
Inductance.
The natural induction causes an overshoot U
motor voltage before it stabilizes itself at a level
depending on the voltage in the intermediate circuit. The
rise time and the peak voltage U
of the motor. In particular, motors without phase coil
insulation are affected if the peak voltage is too high.
Motor cable length affects the rise time and peak voltage.
For example, if the motor cable is short (a few meters), the
rise time and peak voltage are lower. If the motor cable is
long (100 m (328 ft)), the rise time and peak voltage are
higher.
Peak voltage on the motor terminals is caused by the
switching of the IGBTs. The drive complies with the
demands of IEC 60034-25 regarding motors designed to be
controlled by drives. The drive also complies with IEC
60034-17 regarding Norm motors controlled by drives.
High-power range
The power sizes in Table 10.16 to Table 10.21 at the
appropriate mains voltages comply with the requirements
of IEC 60034-17 regarding normal motors controlled by
drives, IEC 60034-25 regarding motors designed to be
controlled by drives, and NEMA MG 1-1998 Part 31.4.4.2 for
inverter fed motors. The power sizes in Table 10.16 to
Table 10.21 do not comply with NEMA MG 1-1998 Part
30.2.2.8 for general purpose motors.
in the
PEAK
affect the service life
PEAK
87
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