130BD930.10
1.80
1.60
1.40
1.20
1.00
0.80
0.60
0.40
0.20
0.00
0 10
20 30 40 50 60 70 80 90 100
N [%]
P
L,CDM
(fr
eq
,load)
[%]
1
2
3
1
100% load
2
50% load
3
25% load
Illustration 3.12 Frequency converter power loss data.
CDM relative losses (P
L, CDM
) [%] versus speed
(n) [% of nominal speed].
130BD931.10
N [%]
0 20 40 60 80 100
100.00
98.00
96.00
94.00
92.00
90.00
η
CDM (fr
eq
,load)
[%]
1
2
3
1
100% load
2
50% load
3
25% load
Illustration 3.13 Frequency converter efficiency data.
CDM efficiency (η
CDM(freq, load)
) [%] versus speed
(n) [% of nominal speed].
Interpolation of power loss
Determine the power loss at an arbitrary operating point
using 2-dimensional interpolation.
3.3.3 Losses and Efficiency of a Motor
The efficiency of a motor running at 50–100% of the
nominal motor speed and at 75–100% of the nominal
torque is practically constant. This is valid both when the
frequency converter controls the motor, or when the motor
runs directly on mains.
The efficiency depends on the type of motor and the level
of magnetisation.
For more information about motor types, refer to the
motor technology brochure at
.
Switching frequency
The switching frequency influences magnetisation losses in
the motor and switching losses in the frequency converter,
as shown in
130B
E107
.10
25
20
15
10
5
0
0
2
4
6
8
10
[kHz]
[%]
1
2
3
1
Motor and frequency converter
2
Motor only
3
Frequency converter only
Illustration 3.14 Losses [%] versus Switching Frequency [kHz]
NOTICE
A frequency converter produces extra harmonic losses in
the motor. These losses decrease when switching
frequency increases.
3.3.4 Losses and Efficiency of a Power Drive
System
To estimate the power losses at different operating points
for a power drive system, sum the power losses at the
operating point for each system component:
•
Frequency converter.
•
Motor.
•
Auxiliary equipment.
3.4 Mains Integration
3.4.1 Mains Configurations and EMC Effects
There are several types of AC mains systems for supplying
power to frequency converters. Each affects the EMC
characteristics of the system. The 5-wire TN-S systems are
regarded as best for EMC, while the isolated IT system is
the least desirable.
System Integration
Design Guide
MG16G202
Danfoss A/S © 08/2015 All rights reserved.
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