Automatic Energy Optimization; Automatic Switching Frequency Modulation; Automatic Derating For High Switching Frequency; Automatic Derating For Overtemperature - Danfoss VLT AQUA Drive FC 202 Design Manual

Product Overview

2.5.8 Automatic Energy Optimization

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Automatic energy optimization (AEO) directs the adjustable
frequency drive to monitor the load on the motor contin-
uously and adjust the output voltage to maximize
efficiency. Under light load, the voltage is reduced and the
motor current is minimized. The motor benefits from
increased efficiency, reduced heating, and quieter
operation. There is no need to select a V/Hz curve because
the adjustable frequency drive automatically adjusts motor
voltage.
2.5.9 Automatic Switching Frequency
Modulation
The adjustable frequency drive generates short electrical
pulses to form an AC wave pattern. The switching
frequency is the rate of these pulses. A low switching
frequency (slow pulsing rate) causes audible noise in the
motor, making a higher switching frequency preferable. A
high switching frequency, however, generates heat in the
adjustable frequency drive which can limit the amount of
current available to the motor.
Automatic switching frequency modulation regulates these
conditions automatically to provide the highest switching
frequency without overheating the adjustable frequency
drive. By providing a regulated high switching frequency, it
quiets motor operating noise at slow speeds, when audible
noise control is critical, and produces full output power to
the motor when required.
2.5.10 Automatic Derating for High
Switching Frequency
The adjustable frequency drive is designed for continuous,
full-load operation at switching frequencies between 3.0
and 4.5 kHz (this frequency range depends on power size).
A switching frequency which exceeds the maximum
permissible range generates increased heat in the
adjustable frequency drive and requires the output current
to be derated.
An automatic feature of the adjustable frequency drive is
load-dependent switching frequency control. This feature
allows the motor to benefit from as high a switching
frequency as the load permits.
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VLT AQUA Drive FC 202
2.5.11 Automatic Derating for
Automatic overtemperature derating works to prevent
tripping the adjustable frequency drive at high
temperature. Internal temperature sensors measure
conditions to protect the power components from
overheating. The drive can automatically reduce its
switching frequency to maintain its operating temperature
within safe limits. After reducing the switching frequency,
the drive can also reduce the output frequency and
current by as much as 30% to avoid an overtemperature
trip.

2.5.12 Auto Ramping

A motor trying to accelerate a load too quickly for the
current available can cause the drive to trip. The same is
true for too quick a deceleration. Auto ramping protects
against these situations by extending the motor ramping
rate (acceleration or deceleration) to match the available
current.

2.5.13 Current Limit Circuit

When a load exceeds the current capability of the
adjustable frequency drive normal operation (from an
undersized converter or motor), current limit reduces the
output frequency to ramp down the motor and reduce the
load. An adjustable timer is available to limit operation in
this condition for 60 s or less. The factory default limit is
110% of the rated motor current to minimize overcurrent
stress.

2.5.14 Power Fluctuation Performance

The adjustable frequency drive withstands line power
fluctuations such as:
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The adjustable frequency drive automatically compensates
for input voltages ±10% from the nominal to provide full
rated motor voltage and torque. With auto restart selected,
the adjustable frequency drive automatically powers up
after a voltage trip. With flying start, the adjustable
frequency drive synchronizes to motor rotation before
start.
Danfoss A/S © 09/2014 All rights reserved.
Overtemperature
Transients
Momentary drop-outs
Short voltage drops
Surges
MG20N622