Inv - FR-A800 - Master Slave Synchronization - Changing rotation direction

Inv - FR-A800 - Master Slave Synchronization - Changing rotation direction

In this article I will describe how to change rotation direction of Slave inverter during synchronization to pulses from Master inverter.
General description of Master - Slave synchronization of FR-A800 inverters with wiring diagrams and parametrization procedure is in attachment - "Master – Slave vector control with FR-A8AL"

In general configuration where phases of encoder from Master inverter are connected to input terminals of A8AL card in Slave inverter, during synchronization ( Pr.419="1" ) Slave inverter follows rotation direction of Master inverter and it's position. There's no possibility of switching direction of Slave inverter (Master run forward and Slave run in reverse) other than electrically switching A and B phases together.

To allow for control of direction, there's possibility to use PULSE/SIGN input mode in Slave inverter. Using this method you need to remember that Slave inverter can no longer follow direction of rotation of Master inverter but only can follow it's position. So when Master inverter will change it's direction, Slave will still rotate in the same direction, synchronizing with pulses from Master inverter.  Keeping that in mind, direction control need to be executed externally for example by PLC.

1. Pulse signal type

Standard signal when using A8AL pulse train input signal from another A800 inverter is two phases pulse train like below:

( Pr.428="5" )

To allow for changing direction without changing A and B phases together we will use PULSE/SIGN mode with only A phase:

( Pr.428="1" or "4" )

But you need to remember that inverter is counting both leading and falling edge in standard signal so when you switch to PULSE/SIGN type, Slave inverter will be rotating 4 times slower then Master. To even speed of Master and Slave you will need to setup an electronic gear in Slave inverter that will be multiplying 4 times incoming pulses.

2. Wiring

To use PULSE/SIGN mode you need to connect A-phase from Master and NP signal like below:

(A8AP can also by used on Master side)

3. Electronic gear 

To ensure that pulses from Master inverter are correctly interpreted you need to set electronic gear with 4/1 ratio. So Pr.420 should be changed to "4" and Pr.421 should remain at "1".


4. Changing direction

To change direction value of Pr.428 should be change between "1" and "4". Changing this parameter change logic of NP input:



Change of direction is possible during rotation but you need to remember that motor will change it's speed without any ramp so overload might occur.


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