NFO
Drives
AB
2021
201013
‐
2
Operating
and
Installation
Manual
35
If negative logic is selected (jumper J801 moved to the “NEG LOG” position), jumper J802 must be in the “OFF”
position and a resistor must be connected according to 4.1.4 Negative logic.
Configuration is carried out under fault
PTC Temp
in parameter group
Error
, see section 5.16.
One, two or three PTC thermistors in series, according to DIN 44081, can be used.
5.12.2 Electronic motor overload protection
The electronic motor overload protection functionality uses the motor parameters in parameter group
Motor
as
described in this manual 5.6. Therefore, it’s essential that these parameters are entered correctly, and that
autotuning is performed.
The protection functionality is controlled by parameters
Overload
,
Amb.Temp
and
Force Cool
.
Overload
can be set
to
Disable
(overload protection disabled),
Indication
(status shown),
Alarm
(generates alarm) or
Fail
(releases
motor). These parameters can be found in the parameter group
Error
and fault
Overload
.
The principle of the electronic motor overload protection is that a motor can operate at an output power loss
equivalent to that of a nominal load (voltage, current and rpm) at an ambient temperature of 20°C, for an unlimited
amount of time.
If the motor is working at a higher output power loss, lower rpm or higher ambient temperature, the electronic motor
overload protection will trip after a period depending on the variable’s ratio (actual voltage, current, rpm and
ambient temperature) in relation to the motor's nominal data.
The actual overload protection status can be read, at any time, as a percentage in the parameter
M-temp
. This
value rises and falls towards a final value corresponding to the current load. The final value of 100.0% corresponds
to nominal load, and the electronic motor overload protection trips when this value is passed.
The ambient motor temperature is set with parameter
Amb.Temp
in the range -20
o
C – +45
o
C. The overload
protection can be triggered at lower motor loads by specifying a higher ambient temperature than it actually is; or a
higher load can be allowed by entering a lower ambient temperature. Default
Amb.Temp
is +20
o
C.
If the motor is equipped with forced cooling, e.g. a cooling fan that is not connected to the motor shaft and thus
cools at a constant rate regardless of motor speed, the parameter
Force Cool
shall be set to a value other than
zero. The overload protection now ignores the motor speed, and replaces it with the value of
Force Cool
. If the
value is set to the same as nominal motor rpm, parameter
N-Nom
, the cooling effect will then be calculated as if the
motor were always running at this speed. Parameter
Force Cool
can be set in the range 0 to 3000, where '0'
indicates that no forced cooling exists.
The Electronic motor overload protection uses thermal memory retention, which means that the calculated relative
temperature of the motor is non-volatile with respect to motor stop/start commands and power cycling (mains
power cycling off/on) of the inverter. The thermal memory retention is non-adjustable (power cycling doesn´t reset
stored value).
If the motor parameters are set correctly and autotuning is performed, the electronic motor overload
protection complies with EN 61800-5-1:2007 / EN 61800-5-1/A1:2017. The protection functionality
operates regardless of motor cable area, cable length, or other cable properties, and regardless of
mains power supply impedance.
WARNING!
If the motor parameters,
Overload
,
Amb.Temp
or
Force Cool
are changed, the Electronic
overload protection can be deactivated and/or not comply with the standards mentioned above.
3006469-2022-04
