Special Conditions; Manual Derating; Automatic Derating - Danfoss VLT AutomationDrive FC 360 Design Manual

Specifications

4.7 Special Conditions

Under some special conditions, where the operation of the
frequency converter is challenged, consider derating. In
some conditions, derating must be done manually.
In other conditions, the frequency converter automatically
performs a degree of derating when necessary. This is
done to ensure the performance at critical stages where
the alternative could be a trip.

4.7.1 Manual Derating

Manual derating must be considered for:
•
Air pressure–for installation at altitudes above 1
km.
•
Motor speed–at continuous operation at low RPM
in constant torque applications.
•
Ambient temperature–above 45 °C (for some
types above 50 °C), for details, see Table 4.15 and
Table 4.16.
Enclosure size Power size Maximum output
[kW] current at 45 °C
0.37
0.55
0.75
J1
1.1
1.5
2.2
3
J2 4
5.5
J3 7.5
11
J4
15
18.5
J5
22
30
J6 37
45
55
J7
75
Table 4.15 Derating at 380 V
MG06B402
Design Guide
Maximum output
current at 50 °C
1.2 1.2
1.7 1.7
2.2 2.2
3.0 3.0
3.7 3.0
5.3 4.1
7.2 7.2
9.0 9.0
12.0 10.2
15.5 13.1
23.0 23.0
31.0 26.0
37.0 37.0
42.5 40.0
61 61
73 73
90 77
106 106
147 125
Danfoss A/S © 09/2014 All rights reserved.
Enclosure size Power size Maximum output
[kW] current at 45 °C
0.37
0.55
0.75
J1
1.1
1.5
2.2
3
J2 4
5.5
J3 7.5
11
J4
15
18.5
J5
22
30
J6 37
45
55
J7
75
Table 4.16 Derating at 480 V

4.7.2 Automatic Derating

The frequency converter constantly checks for critical
levels:
•
Critical high temperature on the control card or
heatsink.
•
High motor load.
•
Low motor speed.
•
Protection signals (overvoltage/undervoltage,
overcurrent, ground fault and short circuit) are
triggered.
As a response to a critical level, the frequency converter
adjusts the switching frequency.
Maximum output
current at 50 °C
1.1 1.1
1.6 1.6
2.1 2.1
3.0 2.8
3.4 2.8
4.8 3.8
6.3 6.3
8.2 8.2
11.0 9.4
14.0 11.9
21.0 21.0
27.0 22.6
34.0 34.0
40.0 37.7
52 52
65 65
77 76
96 96
124 117
59
4 4