Not So Easy Logic

ktmtragic

Member
Join Date
Jan 2013
Location
Sydney
Posts
92
I have a customer who's machine controller died. I managed to find a replacement but it is configured to use a VSD and not two contactors. So motor forward consists of output "motor Forward" all good so far. Reverse is both Forward and "Motor Reverse" outputs simultaneously so it runs forward. Any easy fix ie relays, other than putting in a 2 input PLC.
Thanks
 
Last edited:
Most drives these days have configurable sequencing. It sounds like this setup was for an input for 'Run' and Forward/Reverse, vs. separate Forward and Reverse inputs.

Sure, you can decode either into the the other with a couple of relays. Good class project :)
 
most vsd's have either a 2 wire or 3 wire mode. read the manual or source it if its not with the controller. i think 3 wire may give you a contact for Forward and other contact for Reverse both sharing a common supply wire (3 wire mode)



By the Way i have a KTM300EXC and 2 Honda CR's.
 
Let me be clear this is not a VSD and I can't change the controller output. I need to control 2 relays forward reverse as mentioned above. Like the KTM's have a few !
 
Last edited:
This logic will convert either to the other:

Code:
Run Output => (R1)
Fwd/Rev Output => (R2)

 R1   R2
-][--]/[--> Fwd
-][--][---> Rev

or

Fwd Output => (R3)
Rev Output => (R4)

 R3  
--][--> Run
| R4 |
|-][-|

  R4
--][--> Fwd/Rev
 
I am reading your request that you want a hard wired solution, see attached. The only issue arises when both Enable and Reverse switch on at the same time, a small duration timer fixes that.

Reversing contactors.jpg
 
you still can use 2 relias.
one for activating the motor and another for reversing the motor.
so the relais come in series of each other.
 

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