ABB ACS850 series, Firmware Manual

Page: 46 / 260

46 Program features
Settings
Parameter group 23 Speed ctrl (page 128 ).
Thermal motor protection
The motor can be protected against overheating by
• the motor thermal protection model
• measuring the motor temperature with PTC, KTY84 or Pt100 sensors. This will
result in a more accurate motor model.
„
Thermal motor protection model
The drive calculates the temperature of the motor on the basis of the following
assumptions:
1) When power is applied to the drive for the first time, the motor is at ambient
temperature (defined by parameter
31.09 Mot ambient temp ). After this, when power
is applied to the drive, the motor is assumed to be at the estimated temperature.
2) Motor temperature is calculated using the user-adjustable motor thermal time and
motor load curve. The load curve should be adjusted in case the ambient
temperature exceeds 30 °C.
It is possible to adjust the motor temperature supervision limits and select how the
drive reacts when overtemperature is detected.
Note: The motor thermal model can be used when only one motor is connected to
the inverter.
„
Temperature measurement
It is possible to detect motor overtemperature by connecting a motor temperature
sensor to thermistor input TH of the drive or to optional encoder interface module
FEN-xx.
Constant current is fed through the sensor. The resistance of the sensor increases as
the motor temperature rises over the sensor reference temperature
T
ref
, as does the
voltage over the resistor. The temperature measurement function reads the voltage
and converts it into ohms.