Du/Dt; Efficiency - Danfoss VLT DriveMotor FCP 106 Design Manual

Specifications

6.10 dU/dt

Shaft output power
[kW (hp)]
0.55 (0.75)
0.75 (1.0)
1.1 (1.5)
1.5 (2.0)
2.2 (3.0)
3.0 (4.0)
4.0 (5.0)
5.5 (7.5)
7.5 (10)
6 6
Table 6.10 dU/dt, MH1–MH3
1) Data available at future release.

6.11 Efficiency

Efficiency of the drive (η
The load on the drive has little effect on its efficiency. In
general, the efficiency is the same at the rated motor
frequency f
M,N
rated shaft torque or only 75%, that is if there is part loads.
This also means that the efficiency of the drive does not
change even if other U/f characteristics are selected.
However, the U/f characteristics influence the efficiency of
the motor. The efficiency declines a little when the
switching frequency is set to a value of above 5 kHz. If the
mains voltage is 480 V, the efficiency is also slightly
reduced.
Drive efficiency calculation
Calculate the efficiency of the drive at different loads
based on Illustration 6.6. Multiply the factor in this graph
with the specific efficiency factor listed in the specification
tables.
1.01
1.0
0.99
0.98
0.97
0.96
0.95
0.94
0.93
0.92
0%
100% load
Illustration 6.6 Typical Efficiency Curves
Example: Assume a 22 kW (30 hp), 380–480 V AC drive
runs at 25% load at 50% speed. The graph shows 0.97,
whereas rated efficiency for a 22 kW (30 hp) drive is 0.98.
The actual efficiency is then: 0.97 x 0.98 = 0.95.
58
Motor cable length
[m (ft)]
0.5 (1.6)
0.5 (1.6)
0.5 (1.6)
0.5 (1.6)
<0.5 (1.6)
<0.5 (1.6)
<0.5 (1.6)
<0.5 (1.6)
<0.5 (1.6)
)
VLT
, even if the motor supplies 100% of the
50% 100% 150%
% Speed
75% load 50% load
Danfoss A/S © 12/2018 All rights reserved.
®
VLT DriveMotor FCP 106
Mains voltage
[V]
400
400
400
400
400
400
400
400
400
Efficiency of the motor (η
The efficiency of a motor connected to the drive depends
on the magnetizing level. In general, the efficiency is as
good as with mains operation. The efficiency of the motor
depends on the motor type.
In the range of 75–100% of the rated torque, the efficiency
of the motor is practically constant. The constant efficiency
applies both when a drive controls the motor, and when
the motor runs directly on 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.
In general, 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%). This
improvement is due to an almost perfect sine shape of the
motor current at high switching frequency.
Efficiency of the system (η
To calculate the system efficiency, the efficiency of the
drive (η
VLT
(η ):
MOTOR
η = η
SYSTEM
200%
25% load
Rise time V
peak
[µs] [kV]
0.1 0.57
0.1 0.57
0.1 0.57
0.1 0.57
1) 1)
1) 1)
1) 1)
1) 1)
1) 1)
)
MOTOR
)
SYSTEM
) is multiplied by the efficiency of the motor
x η
VLT MOTOR
dU/dt
[kV/µs]
4.5
4.5
4.5
4.5
1)
1)
1)
1)
1)
MG03M302