Motor Thermal Protection; Safe Torque Off - GE AF-650 GP Design And Installation Manual

Application Set-Up Examples
See parameter B-10 Brake Function and
parameter B-17 Over-voltage Control to select the method
used for controlling the DC-link voltage level.
Mains drop-out
During a mains drop-out, the frequency converter keeps
running until the DC-link voltage drops below the
minimum stop level, which is typically 15% below the
frequency converter's lowest rated supply voltage. The
mains voltage before the drop-out and the motor load
determines how long it takes for the inverter to coast.
Static overload in Advanced Vector Control mode
When the frequency converter is overloaded (the torque
limit in parameter F-40 Torque Limiter (Driving)/
parameter F-41 Torque Limiter (Braking) is reached), the
control reduces the output frequency to reduce the load.
If the overload is excessive, a current may occur that
makes the frequency converter cut out after approximately
5–10 s.
Operation within the torque limit is limited in time (0–60 s)
in parameter SP-25 Trip Delay at Torque Limit.

6.9 Motor Thermal Protection

To protect the application from serious damages General
Purpose Drives offers several dedicated features
Torque Limit: The torque limit feature the motor is
protected for being overloaded independent of the speed.
Torque limit is controlled in parameter F-40 Torque Limiter
(Driving) and or parameter F-41 Torque Limiter (Braking) and
the time before the torque limit warning shall trip is
controlled in parameter SP-25 Trip Delay at Torque Limit.
Current Limit: The current limit is controlled in
parameter F-43 Current Limit and the time before the
current limit warning shall trip is controlled in
parameter SP-24 Trip Delay at Current Limit.
Min Speed Limit: (parameter F-18 Motor Speed Low Limit
[RPM] or parameter F-16 Motor Speed Low Limit [Hz]) limit
the operating speed range to for instance between 30 and
50/60Hz. Max Speed Limit: (parameter F-17 Motor Speed
High Limit [RPM] or parameter F-03 Max Output Frequency 1)
MG35M402
AF-650 GP™ Design and Installation Guide
limit the maximum output speed the frequency converter
can provide
Electronic Thermal Overload: The frequency converter
Electronic Thermal Overload function measures actual
current, speed, and time to calculate motor temperature
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 Illustration 6.28:
Illustration 6.28 Electronic Thermal Overload: The X-axis shows
the ratio between I
the time in seconds before the Electronic Thermal Overload
cut of and trips the frequency converter. 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.

6.10 Safe Torque Off

For information about Safe Torque Off, refer to the Safe
Torque Off Operating Instructions.
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and I nominal. The Y- axis shows
motor motor
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