Altivar 312 Variable Speed Drives Page 13 Introduction

13 Altivar 312 variable speed drives Functions Functions (continued) +/- speed This function is used to increase or decrease a speed reference by means of 1 or 2 logic inputs, with or without the last reference being saved (motorized potentiometer function). This function is suitable for centralized control of a machine with several sections operating in one direction or for control by a pendant control station of a material handling crane with two operating directions. Two types of operation are available: Use of single-action buttons: two logic inputs are required in addition to the operating direction(s). The input assigned to the + speed command increases the speed, the input assigned to the - speed command decreases the speed. Use of double-action buttons (only one logic input assigned to + speed is necessary). Save reference This function is associated with +/- speed control. It enables the last speed reference prior to the loss of the run command or line supply to be read and saved. The saved reference is applied to the next run command. 1 0 1 0 1 0 f (Hz) t Forward or Reverse + speed - speed HSP LSP Motor speed change depending on the skip frequency reference 0 a a b b a a a a c c d a 0 f (Hz) t 2 nd press 1 st press Reverse 2 nd press 1 st press HSP LSP HSP Forward LSP: low speed; HSP: high speed Example with double-action buttons and 1 logic input Note: This type of +/- speed control is incompatible with 3-wire control. a c b d Forward a and c: 1 st press b and d: 2 nd press Reverse + speed Released (- speed) 1st press (speed maintained) 2nd press (+ speed) Forward button - a a and b Reverse button - c c and d Logic inputs:

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