Help on Omron + Freq Inv = Motor Control


Thread Starter


I do some basic PLC programming, but have been asked to interface a FUJI Frequency Inverter to control the speed and direction of a motor. I have never interfaced with a frequency inverter before so this is very new to me.

Move a pallet (loaded or unloaded) along a single axis in two directions (i.e. back and forth).

1. Control Direction
2. Obtain a maximum speed during the long run.
3. Ramp up to max speed from a stopped position.
4. Ramp down from max speed to a stopped position.

I have been reading Omron and Fuji documentation but they assume you know what the hell you are doing - which I do not. I don't know if there is an Omron module(s) that I should use to interface with the Inverter.

The FUJI FRN2.2CTS-4C has a potentiometer inputs. I suspect I will need an Omron analog output module (which one?) to connect to the FUJI so that I can control the frequency (i.e. motor speed).

Can anyone give me some advice?
Is there a specific Omron module(s) I should use?
What traps should I be watch out for?
Recommended documentation?
I haven't used the Fuji drive but the brochure I am looking at shows 4-20 mA input for speed set-point on terminals C1 & 11 if not the potentiometer input will accept a 0 - 10 Volts between 12 & 11, just provide either from the PLC.
For direction I would use a relay output module, they are less hassle than solid state variety, just wire 1 NO contact to FWD & CM and another to REV and CM.

There are many ways to generate a ramp in the PLC, using count up/down or add and subtract to name a couple or you could use the drives internal ramp function.

Hope it helps
Thanks Roy for your assistance.

I am thinking an Omron CJ1W-DA021 module would be sufficient for speed control.

But, I have been studying the Fuji manual and it has the ability to be programmed for ramp up and ramp down and max speed. Since the linear distance the pallet moves is constant should I just program the Fuji inverter to perform the task and skip trying to adjust the speed from the PLC? Is this a good practice or should I plan on controlling the motor myself? I fear the Fuji may not always stop in the proper position (having no experience with inverters). Is it just as simple as placing a normally closed limit switch at each stop position and have the Fuji ramp down to a crawl and continue at that speed until the limit switch is tripped?

William Sturm

Using the drive speed setpoints and two limit switches, one for slow and one for stop would probably be simpler than trying to do this in the PLC. It has been done many times before.

You might feed the switches into the PLC and use PLC discrete outputs to control the drive. This way, you can latch the inputs or add time delays.

The main issue is repeatability, there are many variables at work. You can control repeatability to a large extent by adjusting the slow speed rate in the drive. You can adjust the final position by changing the drive decel rate, moving the switch, or adjusting a time delay on the stop output.
Yes, I think you are on the right track. You could forget the analog input option and use the digital inputs X1, X2, X3 to control the speed.
For example closing X1 for 10% speed, X2 for 100% speed;\.

As you approach the end point limit switch for X2 opens and the drive ramps down to 10%. It then creeps until limit switch opens the FWD or REV then stops.

Good luck
Thanks to everyone for their input! You have all been real helpful! One more quick question:

The motor-gearbox has a break. It appears to be wired to one leg of the three-phase input. Should I just leave the break connected to the motor electrical feed (i.e break=off when power applied) or do I need to control the break via the Frequency Inverter (I don't see how to this with the Freq. Inverter) or control the break via the PLC?

I think I am inclined to leave the break alone and let it function (release) when the power is applied to the motor by the Frequency Inverter.