Special Conditions; Temperature-Related Switching Frequency; Derating For Long Motor Cables; Vlt 2800 Start-Up - Danfoss VLT 2800 Series General Information Manual

Special conditions

Derating for ambient temperature
The ambient temperature (T
temperature allowed. The average (T
ured over 24 hours, must be at least 5 °C lower. If the
frequency converter operates at temperatures above
45 °C, a derating of the rated output current is neces-
sary.

Temperature-related switching frequency

This function ensures the highest possible switching
frequency without the adjustable frequency drive be-
coming thermally overloaded. The internal tempera-
ture determines the switching frequency based on the
load, the ambient temperature, the supply voltage and
the cable length. The function ensures that the drive
automatically adjusts the switching frequency between
the minimum and maximum switching frequency (pa-
rameter 411), see drawing below.
When using the LC filter the minimum switch frequen-
cy is 4.5 kHz.
®
MG.27.A2.22 - VLT is a registered Danfoss trademark
) is the maximum
AMB,MAX
) meas-
AMB,AVG
®
VLT 2800 Series

Derating for long motor cables

The adjustable frequency drive has been designed for
a 240 ft (75 m) unscreened/unarmored cable or a 80
ft (25 m) screened/armored cable and a motor cable
with a rated cross-section. If a cable with a larger
cross-section is required, it is recommended to reduce
the output current by 5% for each step that the cable
cross-section is increased. (Increased cable cross-
section leads to increased capacitance to ground, and
thus to an increased ground leakage current.)

VLT 2800 start-up

Pre-installation checks
1. Compare drive model number to what was
ordered.
2. Ensure each of following are rated for same
voltage:
• Drive
• Power line
• Motor
3. Record following motor data:
• Voltage
• Frequency
• Full load current
• Full load speed
• Power - convert HP to kW (See con-
version table in parameter 102, Mo-
tor Power, in this manual.)
4. Ensure that rated drive current is equal to or
greater than total full load current.
• Drive can be at most one size small-
er than motor.
• For multiple motor operations, add
full load current ratings of all motors.
• If drive rating is less than motor(s),
full motor output cannot be ach-
ieved.
5. Check motor wiring:
• Any disconnect between drive and
motor should be interlocked to drive
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