Let's clarify the details regarding such functionality at first :
1. Inverter temperature goes hand in hand with inverter losses. The losses depend on several factors, but mainly on motor current and switching frequency.
2. Reduction in the speed can work only in the case of quadratic or linear torque (pumps, fans, compressors, etc.). In the case of constant torque application, the current will not drop at a lower speed, so a reduction in speed does not lead to lowering the losses and eventually drive will trip.
3. With reducing the switching frequency the losses will be lower, but such an option is not automatic. The switching frequency cannot be modified in the running state or switched to another value by a digital signal.
4. If the size of inverter is selected properly according to motor data and application cycle, and with respect to environmental conditions, the drive should never reach the overtemperature. However, it is obvious that if the size of the inverter is not enough, this function could prolong operation before the overtemperature fault or avoid the fault entirely.
What you can do (speaking about the Altivar Process) is here in 2 possibilities:
a) to assign relay output to "drive thermal state reached" and wire this relay output to one of the digital inputs assigned to preset speed for example. The threshold for "drive thermal state reached" is done using THA drive thermal state warning.
b) to use drive overload monitoring (in menu Error/warning management) and define OHL=fallback speed and THA (thermal state warning)=xx %. Do no forget to configure fallback speed LFF.
1. Inverter temperature goes hand in hand with inverter losses. The losses depend on several factors, but mainly on motor current and switching frequency.
2. Reduction in the speed can work only in the case of quadratic or linear torque (pumps, fans, compressors, etc.). In the case of constant torque application, the current will not drop at a lower speed, so a reduction in speed does not lead to lowering the losses and eventually drive will trip.
3. With reducing the switching frequency the losses will be lower, but such an option is not automatic. The switching frequency cannot be modified in the running state or switched to another value by a digital signal.
4. If the size of inverter is selected properly according to motor data and application cycle, and with respect to environmental conditions, the drive should never reach the overtemperature. However, it is obvious that if the size of the inverter is not enough, this function could prolong operation before the overtemperature fault or avoid the fault entirely.
What you can do (speaking about the Altivar Process) is here in 2 possibilities:
a) to assign relay output to "drive thermal state reached" and wire this relay output to one of the digital inputs assigned to preset speed for example. The threshold for "drive thermal state reached" is done using THA drive thermal state warning.
b) to use drive overload monitoring (in menu Error/warning management) and define OHL=fallback speed and THA (thermal state warning)=xx %. Do no forget to configure fallback speed LFF.
Publié pour: Schneider Electric Belgium
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