Altivar 312 Variable Speed Drives Page 11 Introduction

11 Altivar 312 variable speed drives Functions Functions (continued) Voltage/frequency ratio Motor and power supply specifications This function is used to determine the limit values for the voltage/frequency ratio according to the specifications of the line supply, motor and application. The following values should be set for constant or variable torque applications with or without overspeed: - The base frequency corresponding to the line supply - The nominal motor frequency (in Hz) given on the motor rating plate - The nominal motor voltage (in V) given on the motor rating plate - The maximum output frequency of the drive (in Hz) Type of voltage/frequency ratio This is used to adapt the voltage/frequency ratio to the application in order to optimize performance for the following applications: Constant torque applications (machines with average loads operating at low speed) with motors connected in parallel or special motors (e.g. resistive cage motor): ratio L Variable torque applications (pumps, fans): ratio P Machines with heavy loads operating at low speed, machines with fast cycles, with (sensorless) flux vector control: ratio n Energy saving, for machines with slow torque and speed variations: ratio nLd. The voltage is automatically reduced to minimum according to the necessary torque. L n P U (V) Un frn f (Hz) Un: nominal motor voltage frn: nominal motor frequency Auto-tuning Auto-tuning can be performed: Voluntarily by the operator using dialog tools via local control or the serial link Each time the drive is switched on On each run command By enabling a logic input Auto-tuning is used to optimize application performance. Switching frequency, noise reduction Adjusting the switching frequency setting reduces the noise generated by the motor. The switching frequency is modulated randomly in order to avoid resonance. This function can be disabled if it causes instability. High frequency switching of the intermediate DC voltage can be used to supply the motor with a current wave that has little harmonic distortion. The switching frequency can be adjusted during operation to reduce the noise generated by the motor. Value: 2 to 16 kHz. Factory setting 4 kHz For all applications which require low motor noise.

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