66 Program features
The motor temperature can be monitored using
• the motor thermal protection model (estimated temperature derived internally
inside the drive), or
• sensors installed in the windings. This will result in a more accurate motor model.
Motor thermal 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 assumed to be at
ambient temperature (defined by parameter 35.50 Motor ambient temperature).
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.
The motor thermal protection model fulfills standard IEC/EN 61800-5-1 ed. 2.1
requirements for thermal memory retention and speed sensitivity. The estimated
temperature is retained over power down. Speed dependency is set by parameters
35.51 Motor load curve, 35.52 Zero speed load and 35.53 Break point.
Note: The motor thermal model can be used when only one motor is connected to
the drive.
Temperature monitoring using PTC sensors
One PTC sensor can be connected to digital input DI6.
The resistance of the PTC sensor increases when its temperature rises. The
increasing resistance of the sensor decreases the voltage at the input, and eventually
its state switches from 1 to 0, indicating overtemperature.
1…3 PTC sensors can also be connected in series to an analog input and an analog
output. The analog output feeds a constant excitation current of 1.6 mA through the
sensor. The sensor resistance increases as the motor temperature rises, as does the
voltage over the sensor. The temperature measurement function calculates the
resistance of the sensor and generates an indication if overtemperature is detected.
For wiring of the sensor, refer to the Hardware Manual of the drive.
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