Altivar 312 Variable Speed Drives Page 12 Introduction

12 Altivar 312 variable speed drives Functions Functions (continued) Skip frequencies This function suppresses one or two critical speeds that may cause mechanical resonance. It is possible to prohibit prolonged operation of the motor on 1 or 2 frequency bands ( 1 Hz), around an adjustable frequency on the speed range. This function is suitable for lightweight machines, bulk product conveyors with an unbalanced motor, fans and centrifugal pumps. Speed reference The speed reference can come from different sources, depending on the drive configuration: References provided by 3 analog inputs The navigation button reference The +/- speed function via logic input, using the keypad or remote display terminal keys The remote display terminal reference Speed references provided by the communication bus or networks These sources are managed by programming the reference functions and channels. Analog inputs There are 3 analog inputs: 2 voltage inputs: - 0-10 V (AI1) - 10 V (AI2) 1 current input: - X-Y mA (AI3), where X is configurable between 0 and 20 mA, and Y is configurable between 4 and 20 mA Preset speeds This function is used to switch preset speed references. Choose between 2, 4, 8 or 16 preset speeds. Enabled by means of 1, 2, 3 or 4 logic inputs. The preset speeds are adjustable in increments of 0.1 Hz from 0 Hz to 500 Hz. This function is suitable for material handling and machines with several operating speeds. 2 Hz Reference f (Hz) Motor speed change depending on the skip frequency reference 1 10 15 20 1 LI3 0 1 LI4 0 LI2 0 t f (Hz) LSP Forward or Reverse The speed obtained with inputs LI3 and LI4 at state 0 is LSP or the speed reference, depending on the level of analog inputs AI1, AI2 and AI3. Factory settings: 1 st speed: LSP (low speed or speed reference) 2 nd speed: 10 Hz 3 rd speed: 15 Hz 4 th speed: 20 Hz (high speed) Example of switching using lgic input LI4

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