4.10.4 Derating for Running at Low Speed
When a motor is connected to a frequency converter, it is necessary to check that the cooling of the motor is adequate.
The level of heating depends on the load on the motor, as well as the operating speed and time.
Variable (Quadratic) torque applications (VT)
In VT applications such as centrifugal pumps and fans, where the torque is proportional to the square of the speed and the power is proportional to the cube of
the speed, there is no need for additional cooling or de-rating of the motor.
In the graphs shown below, the typical VT curve is below the maximum torque with de-rating and maximum torque with forced cooling at all speeds.
Maximum load for a standard motor at 40
°
C driven by an AF-600 FP drive
Legend:
─ ─ ─ ─
Typical torque at VT load
─•─•─•─
Max torque with forced cooling
‒‒‒‒‒
Max torque
Note 1) Over-syncronous speed operation will result in the available motor torque decreasing inversely proportional with the increase in speed. This must
be considered during the design phase to avoid over-loading of the motor.
4.10.5 Automatic Tuning to Ensure Performance
The frequency converter constantly checks for critical levels of internal temperature, load current, high voltage on the intermediate circuit and low motor speeds.
As a response to a critical level, the frequency converter can adjust the switching frequency and/ or change the switching pattern in order to ensure the performance
of the drive.
AF-650 GP Design Guide
88
4
Summary of Contents for AF-650 GP Series
Page 5: ...AF 650 GP Design Guide 4 1...
Page 53: ...AF 650 GP Design Guide 52 4...
Page 97: ...Please note airflow directions 6 1 5 Mechanical Dimensions AF 650 GP Design Guide 96 6...
Page 98: ...Please note airflow directions AF 650 GP Design Guide 97 6...
Page 99: ...Please note airflow directions AF 650 GP Design Guide 98 6...
Page 100: ...Please note airflow directions AF 650 GP Design Guide 99 6...
Page 173: ...Max cable length 150 m AF 650 GP Design Guide 172 9...
Page 179: ...AF 650 GP Design Guide 178 9...