Example: Assume a 160 kW, 380–480/500 V AC drive at
25% load at 50% speed.
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
(15 hp) and up, the advantages are significant.
Typically the switching frequency does not affect the
efficiency of small motors. Motors from 11 kW (15 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
VLT
) is multiplied by the efficiency 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 filter choke.
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 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
.
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) and the inductance.
The natural induction causes an overshoot U
PEAK
in the
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
PEAK
affect the service life
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.
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 60034-25:2007 edition 2.0 regarding
motors designed to be controlled by drives. The drive also
complies with IEC 60034-17:2006 edition 4 regarding Norm
motors controlled by drives.
High-power range
The power sizes in
to
at the
appropriate mains voltages comply with the requirements
of IEC 60034-17:2006 edition 4 regarding normal motors
controlled by drives, IEC 60034-25:2007 edition 2.0
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
to
do not comply
with NEMA MG 1-1998 Part 30.2.2.8 for general purpose
motors.
Electrical Installation Con...
VLT® AutomationDrive FC 302
160
Danfoss A/S © 01/2018 All rights reserved.
MG38C202
10
10
