Danfoss VLT Midi Drive FC 280 Design Guide

Enclosure size Power [kW (hp)] Non-UL fuse Non-UL circuit breaker UL fuse
K1
0.37 (0.5)
gG-10
PKZM0-16
JJS-3
0.55–0.75
(0.74–1.0)
JJS-6
1.1–1.5
(1.48–2.0)
gG-20
JJS-10
2.2 (3.0) JJS-15
K2
3.0–5.5
(4.0–7.5)
gG-25 PKZM0-20 JJS-25
K3
7.5
(10)
gG-25 PKZM0-25 JJS-25
K4
11–15
(15–20)
gG-50 – JJS-50
K5
18.5–22
(25–30)
gG-80 – JJS-80
Table 7.4 Fuse and Circuit Breaker, 380–480 V
7.9 Eciency
Eciency of the frequency converter (η
VLT
)
The load on the frequency converter has little eect on its
eciency. In general, the eciency is the same at the
rated motor frequency f
M,N
. This rule also applies even if
the motor supplies 100% of the rated shaft torque or only
75%, for example if there is part loads.
This also means that the eciency of the frequency
converter does not change even if other U/f characteristics
are selected.
However, the U/f characteristics inuence the eciency of
the motor.
The eciency declines a little when the switching
frequency is set to a value above the default value. If the
mains voltage is 480 V, or if the motor cable is longer than
30 m (98.4 ft), the eciency is also slightly reduced.
Frequency converter eciency calculation
Calculate the eciency of the frequency converter at
dierent loads based on Illustration 7.2. Multiply the factor
in Illustration 7.2 by the specic eciency factor listed in
the specication tables in chapter 7.1 Power-dependent
Specications:
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
Illustration 7.2 Typical Eciency Curves
Eciency of the motor (η
MOTOR
)
The eciency of a motor connected to the frequency
converter depends on the 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 controlled
by the frequency converter and when running directly on
mains.
In small motors, the inuence from the U/f characteristic
on eciency is marginal. However, in motors from 11 kW
(14.8 hp) and up, the advantages are signicant.
In general, the switching frequency does not aect the
eciency of small motors. Motors from 11 kW (14.8 hp)
and up have their eciency improved 1–2% because the
sine shape of the motor current is almost perfect at high
switching frequency.
Eciency of the system (η
SYSTEM
)
To calculate the system eciency, the eciency of the
frequency converter (η
VLT
) is multiplied by the eciency of
the motor (η
MOTOR
):
η
SYSTEM
= η
VLT
x η
MOTOR
Specications
VLT
®
Midi Drive FC 280
82 Danfoss A/S © 03/2016 All rights reserved. MG07B102
77

Danfoss VLT Midi Drive FC 280 Specifications

General

Brand	Danfoss
Model	VLT Midi Drive FC 280
Category	DC Drives
Language	English