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How do I use Acceleration and Deceleration current limits?

The PL/X has two externally set current limit – one for positive current, the parameter known as 89)UPPER CURRENT CLAMP and one for negative current known as 90)LOWER CURRENT CLAMP. These are controlled by default by terminals UIP6 and UIP5 respectively, although if you want to use them both you need to set 88)DUAL I CLAMP ENBL to ENABLED – by default, 88)DUAL I CLAMP ENBL is controlled by T21 (DIO4) so you can either take T21 to +24V or set DIO4 GOTO to 400)BLOCK DISCONNECT and set 88)DUAL I CLAMP ENBL to ENABLED manually.

When rotating forwards acceleration current is usually positive and deceleration current is negative – when rotating in reverse, the opposite is true although it depends on the load characteristic of course. It can sometimes be useful to control acceleration current and deceleration current independently irrespective of rotation direction. All it needs is for the upper and lower current clamps to be swapped when rotating in reverse. You could arrange for the two signals to UIP5 and 6 to be swapped over externally, but the following allows automatic change over – so you all you need to do is to provide UIP6 and 5 with a 0 to 10V signal each, then UIP5 controls deceleration current limit from 0 to -150% and UIP6 controls acceleration current limit from 0 to 150% irrespective of direction. (If you want a lower current limit, say 100%, to be represented by 10V it is just a case of changing the UIP CAL RATIO – 362)UIP6 CAL RATIO in the case of UIP6).

Go to CONFIGURATION, ENABLE GOTO,GETFROM and set to ENABLED.

If you haven’t connected T24 (DIO4) to 24V, go to CONFIGURATION, DIGITAL IN/OUTPUTS, DIO4 (T21) SETUP and set it’s GOTO to 400)BLOCK DISCONNECT. Also go to CHANGE PARAMETERS, CURRENT CONTROL and set 88)DUAL I CLAMP ENBL to ENABLED.

Go to CONFIGURATION, JUMPER CONNECTIONS, JUMPER 1 and set it’s GET FROM to 26)RAMP INPUT or whatever is appropriate for the speed input you are using and it’s GOTO to 588)COMP1 INPUT1. Go to APPLICATION BLOCKS, COMPARATOR 1 and set it’s GOTO to 604)C/O SW1 CONTROL and 591)COMP1 HYSTERESIS to 0.00.

The above sets up COMPARATOR 1 to go high when the speed demand is below 0 (reverse speed demand). It is going to control two changeover switches, SW1 and SW2.

Go to CONFIGURATION, UNIVERSAL INPUTS, UIP6 SETUP and set its GOTO to 605)C/O SW1 HI VALUE.
Go to CONFIGURATION, UNIVERSAL INPUTS, UIP5 SETUP and set its GOTO to 606)C/O SW1 LO VALUE.
Go to CONFIGURATION, JUMPER CONNECTIONS, JUMPER 2 and set its GETFROM to 604)C/O SW1 CONTROL and its GOTO to 607)C/O SW2 CONTROL.
Go to CONFIGURATION, JUMPER CONNECTIONS, JUMPER 3 and set its GETFROM to 606)C/O SW1 LO VALUE and its GOTO to 608)C/O SW2 HI VALUE.
Go to CONFIGURATION, JUMPER CONNECTIONS, JUMPER 4 and set it’s GETFROM to 605)C/O SW1 HI VALUE and its GOTO to 609)C/O SW2 LO VALUE.
Go to APPLICATION BLOCKS, C/O SWITCH 1 and set its GOTO to 300)ANALOG POST 1.
Go to APPLICATION BLOCKS, C/O SWITCH 2 and set it’s GOTO to 89) UPPER CUR CLAMP.
Go to APPLICATION BLOCKS, MULTI-FUNCTION 1 and set 544)MULTFUN1 MODE to SIGN CHANGER, 545)MULTIFUN1 OP SEL to ENABLED, GETFROM to 300)ANALOG POST 1 and its GOTO to 90)LOWER CUR CLAMP.

The above does the switching for 89) and 90) and also inverts to signal used for 90)LOWER CUR CLAMP so that you can use a positive signal into UIP5.

Go to CONFIGURATION, ENABLE GOTO,GETFROM and set to DISABLED.

Once you are happy, don't forget to do a PARAMETER SAVE.

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