Derating For Air Pressure; Derating For Running At Low Speed; Derating For Long Motor Cables Or Cables With Larger Cross-Section; Derating For High Switching Frequency - Danfoss VLT 7000 Series Manual

Derating for air pressure

Below 1000 m altitude no derating is necessary.
Above 1000 m the ambient temperature (T
max. output current (I
VLT,MAX
accordance with the diagram below:

Derating for running at low speed

When a centrifugal pump or a fan is controlled by a VLT
7000 Booster frequency converter, it is not necessary
to reduce the output current at low speed because
the load characterstic of the centrifugal pumps/fans,
automatically ensures the necessary reduction.
Derating for long motor cables or cables
with larger cross-section
VLT 7000 Booster has been tested using 300
m unscreened/unarmoured cable and 150 m
screened/armoured cable.
VLT 7000 Booster has been designed to work using a
motor cable with a rated cross-section. If a cable with
a larger cross-section is to be used, it is recommended
to reduce the output current by 5% for every step
the cross-section is increased. (Increased cable
cross-section leads to increased capacity to earth,
and thus an increased earth leakage current).

Derating for high switching frequency

A higher switching frequency (to be set in parameter
407, Switching frequency) leads to higher losses in
the electronics of the frequency converter.
122
) or
AMB
) must be derated in
VLT® 7000 Booster
1. Derating of output current versus altitude
at T = max. 45°C
AMB
2. Derating of max. T
AMB
100% output current.
VLT 7000 Booster has a pulse pattern in which
it is possible to set the switching frequency
from 3.0- 10.0/14.0 kHz.
The frequency converter will automatically derate
the rated output current I
VLT,N,
frequency exceeds 4.5 kHz.
In both cases, the reduction is carried out
linearly, down to 60% of I
VLT,N
The table gives the min., max. and factory-set
switching frequencies for VLT 7000 Booster units.
Switching frequency [kHz]
VLT 7002-7011, 460 V
VLT 7016-7062, 460 V
VLT 7072, 460 V
MG.70.A1.02 - VLT is a registered Danfoss trademark
versus altitude at
when the switching
.
Min. Max. Fact.
3.0 10.0 4.5
3.0 14.0 4.5
3.0 4.5 4.5