Derating must be taken into account when using the frequency converter at low air pressure (heights), at low speeds, with long motor cables, cables with a large

cross section or at high ambient temperature. The required action is described in this section.

7.6.2 Derating for Ambient Temperature

90% frequency converter output current can be maintained up to max. 50 °C ambient temperature.

With a typical full load current of EFF 2 motors, full output shaft power can be maintained up to 50 °C.

For more specific data and/or derating information for other motors or conditions, please contact GE.

7.6.3 Automatic Adaptations to Ensure Performance

The frequency converter constantly checks for critical levels of internal temperature, load current, high voltage on the intermediate circuit and low motor speeds.

As a response to a critical level, the frequency converter can adjust the switching frequency and / or change the switching pattern in order to ensure the

performance of the frequency converter. The capability to automatically reduce the output current extends the acceptable operating conditions even further.

7.6.4 Derating for Low Air Pressure

The cooling capability of air is decreased at lower air pressure.

Below 1000 m altitude no derating is necessary but above 1000 m the ambient temperature (T

with the shown diagram.

Illustration 7.2: Derating of output current versus altitude at T

PELV.

An alternative is to lower the ambient temperature at high altitudes and thereby ensure 100% output current at high altitudes. As an example of how to read the

graph, the situation at 2 km is elaborated. At a temperature of 45° C (T

100% of the rated output current is available.

) or max. output current (I

AMB

for unit sizes 1x, 2x and 3x. At altitudes above 2 km, please contact GE regarding

AMB, MAX

- 3.3 K), 91% of the rated output current is available. At a temperature of 41.7° C,

AMB, MAX

AF-600 FP Design Guide

) should be derated in accordance

out

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