Overload Protection; Locked Rotor Protection; Automatic Derating; Overview Of Automatic Derating - Danfoss VLT AQUA FC 202 Design Manual

VLT® AQUA Drive FC 202
Design Guide

6.1.7 Overload Protection

Torque limit
The torque limit feature protects the motor against overload, independent of the speed. Torque limit is controlled in parameter 4-16
Torque Limit Motor Mode and parameter 4-17 Torque Limit Generator Mode. The time before the torque limit warning trips is control-
led in parameter 14-25 Trip Delay at Torque Limit.
Current limit
The current limit is controlled in parameter 4-18 Current Limit, and the time before the drive trips is controlled in parameter 14-24 Trip
Delay at Current Limit.
Speed limit
Minimum speed limit: Parameter 4-11 Motor Speed Low Limit [RPM] or parameter 4-12 Motor Speed Low Limit [Hz] limit the minimum
operating speed range of the drive. Maximum speed limit: Parameter 4-13 Motor Speed High Limit [RPM] or parameter 4-19 Max Out-
put Frequency limit the maximum output speed the drive can provide.
Electronic thermal relay (ETR)
ETR is an electronic feature that simulates a bimetal relay based on internal measurements. See
Voltage limit
The inverter turns off to protect the transistors and the DC link capacitors when a certain hard-coded voltage level is reached.
Overtemperature
The drive has built-in temperature sensors and reacts immediately to critical values via hard-coded limits.

6.1.8 Locked Rotor Protection

There can be situations when the rotor is locked due to excessive load or other factors. The locked rotor cannot produce enough
cooling, which in turn can overheat the motor winding. The drive is able to detect the locked rotor situation with PM VVC+ control
(parameter 30-22 Locked Rotor Detection).

6.1.9 Automatic Derating

The drive constantly checks for critical levels:
• Critical high temperature on the control card or heat sink.
• High motor load.
• High DC-link voltage.
• Low motor speed.
As a response to a critical level, the drive adjusts the switching frequency. For critical high internal temperatures and low motor
speed, the drive can also force the PWM pattern to SFAVM.
DERATING WITH SINE-WAVE FILTER
The automatic derating is different when parameter 14-55 Output Filter is set to [2] Sine-Wave Filter Fixed.
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Refer to the programming guide for more information.

6.1.9.1 Overview of Automatic Derating

The automatic derating is made up of contributions from separate functions that evaluate the need. Their interrelationship is shown
in Illustration 25.
In sine-wave filter fixed mode, the structure is different.
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See 6.1.9.2 Sine-wave Filter Fixed
Danfoss A/S © 2020.09
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Mode.
Product Features
6.2.2 Motor Thermal Protection.
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