Torque Limit: The Torque limit feature the motor is protected for being overloaded independent of the speed. Torque limit is controlled in par. F-40 Torque Limiter

(Driving) and or par. F-41 Torque Limiter (Braking) and the time before the torque limit warning shall trip is controlled in par. SP-25 Trip Delay at Torque Limit.

Current Limit: The current limit is controlled in par. F-43 Current Limit and the time before the current limit warning shall trip is controlled in par. SP-24 Trip Delay

at Current Limit.

Min Speed Limit: (par. F-18 Motor Speed Low Limit [RPM] or par. F-16 Motor Speed Low Limit [Hz]) limit the operating speed range to for instance between 30 and

50/60Hz. Max Speed Limit: (par. F-17 Motor Speed High Limit [RPM] or par. F-03 Max Output Frequency 1) limit the max output speed the drive can provide

Electronic Thermal Overload: The frequency converter Electronic Thermal Overload function measures actual current, speed and time to calculate motor tem-

perature and protect the motor from being overheated (Warning or trip). An external thermistor input is also available. Electronic Thermal Overload is an electronic

feature that simulates a bimetal relay based on internal measurements. The characteristic is shown in the following figure:

Illustration 3.5: Figure Electronic Thermal Overload: The X-axis shows the ratio between I

before the Electronic Thermal Overload cut of and trips the drive. The curves show the characteristic nominal speed, at twice the nominal speed

and at 0,2 x the nominal speed.

At lower speed the Electronic Thermal Overload cuts of at lower heat due to less cooling of the motor. In that way the motor are protected from

being over heated even at low speed. The Electronic Thermal Overload feature is calculating the motor temperature based on actual current and

speed. The calculated temperature is visible as a read out parameter in par. DR-18 Motor Thermal in the AF-650 GP.

AF-650 GP Design Guide

and I

nominal. The Y- axis shows the time in seconds

motor

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