Ok, here goes.
I have a ventilation project for a car workshop, I am building new premises for myself and wanted a smart system. I ended up learning how to program a Siemens Logo PLC. It gives me the freedom to embed a few different functions to each other (ventilation, exhaust extraction, etc). My PLC is one with relay outputs, and now I have programmed it in a way that one relay output is used for each of four fan speeds I was planning to have.
no output active=fan stopped
Output 1 active=fan speed 1
Output 2 active=fan speed 2
Output 3 active=fan speed 3
Output 4 active=fan speed 4
Later I found out that one output might need to feed 2 logic inputs on the Altivar, I think this is done easiest by using diodes in the wiring between the PLC and the Altivar.
Now to the Altivar 12...M2. It has 4 logic inputs, and I initially thought I could just use one at a time to activate 4 different pre-programmed frequency outputs. All the basic configuration is there (electric motor specs), I was able to use it in local mode adjusting frequency output on the wheel.
Then it gets confusing to me. The user manual (5/2013) says 2- or 3-wire control. 2-wire control is sufficient if you want 4 different speeds but if one of those 4 speeds is 0 (motor stopped) I have only 3 running speeds left? Or, is it that one of the logic inputs needs to be a RUN command, and depending on the input states of these 2 control wires you could have 4 running speeds?
On page 69 of the user manual is a table showing I/O states for the different speed settings. One thing I don't understand at all is that there is no such thing as Preset speed 1, instead there is "reference". What is this?
Another thing that confuses me is that I have selected POS as for positive signal to mean a logic input is 1, but when I look at the input statuses in the maintenance view, it shows me each input is high when I use a jumper cable from each input to COM. Jumping +24V to the inputs doesn't do a thing. What of the wiring is necessary for my needs, is it enough to use the PLC relay outputs to connect the +24V to the logic inputs I need, or does it also need the jumper to LO- ? How about these AI1/+5V/COM, do I have to wire these even if I don't need them for any feedback or control? Messing with the setting I did configure it to 8 preset speeds, ending up in a situation I can't even start the motor in local mode anymore.. Jumping the logic inputs in remote mode doesn't do anything either..
I would really appreciate if someone could walk me through this, I have no clue of the correct setting and wiring.
Thank you very much in advance.
Your assumption about using one digital output to get one of X fan speeds is not correct. That's not the way the drive works.
The drive does have the capability for 4 preset speeds, but it does so using combinations of the binary states on its digital inputs, using 2 DI's for 4 speeds and one DI for run/stop.
I found the Altivar 12 User manual (dated 05/2013) here:
Page 37 describes the Reference Mode, which value or signal the unit uses as a setpoint or desired frequency.
2) There is an application note showing exactly what you want to do on page 116 - 4 preset speeds with run/stop.
The diagram shows 3 digital inputs wired as sourcing inputs using the unit's +24V supply.
There's a screen shot of the app note here:
Digital input (DI) #1, LI1 is the run/stop switch
Digital input #2, LI2 is the low order binary coded 4 speed switch
Digital input #3, LI3 is the high order binary coded 4 speed switch
The application note goes on to give examples of navigating through the setup to
- configure "4 Preset Speeds" as the operating mode
- configure the frequency value for Preset Speed 2. It assumes you can configure the freq values for Preset Speeds 3 and 4 on your own, once you know how to get there.
User manual page 70 has the PSS Preset speed menu items.
Four speeds can be selected by 2 binary bits with the combinations 00, 01, 10, 11.
Those binary codes are shown on page 69 where LI2 is PS2 in the table and LI3 is PS4
When LI2 and LI3 are both OFF (or open), the binary code is 00, which selects the reference speed.
When LI2 is ON and LI3 is OFF, the binary code is 01, which selects SP 2 (speed 2)
When LI2 is OFF and LI3 is ON, the binary code is 10, which selects SP3 (speed 3)
When LI2 is ON and LI3 is ON, the binary code is 11, which selects SP4 (speed4)
So, yes, you get RUN/STOP and Four speeds using 3 digital outputs from the PLC wired to the DI's on the Altivar.
I assume that calling the factory program configures LI1 as the run/stop DI, because that step is not spelled out separately in the app.
> is it enough to use the PLC relay outputs to connect the +24V to the logic inputs I need, or does it also need the jumper to LO- ?
You need to wire the relay outputs as shown in the application:
- the Altivar +24V goes to one side of the relay contact (that's considered 'sourcing')
- the other side of the relay contact goes to a LIx digital input
I suspect that the DI's don't do anything (perform any function) in factory mode (as it comes out of the box) until the DI's are configured, which is why playing around with them did nothing.