# Incremental Encoder



## fjl810 (Jul 20, 2011)

I will be replacing a SECO 2 hp 460 volt ac flux vector drive with most likely an Allen Bradley Power flex 40P.
The question is the seco drive encoder has A, A- , B , B- and Z, Z-.
The power flex doesn't have Z terminals, can I use this encoder and not use the Z wiring, or do I need a different encoder or drive.
Thanks for any help.


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## varmit (Apr 19, 2009)

What is your application? Unless you are doing finite positioning control, or coordinated web handling, sensorless vector control is rated to be within 0.03% of the speed accuracy of encoder feedback. The A an B encoder inputs give a pulse input for each count of the encoder. A 1096 PPR encoder gives 1096 counts on the A and B channels per revolution. The Z input is one pulse per revolution. most software uses the Z input as a check to see if the A an B pulse count total is correct when the Z pulse toggles. If you connect the encoder to the AB drive, the encoder will still do it's job with the Z channel not connected.


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## fjl810 (Jul 20, 2011)

The drive is for the left carriage (Tool Holder) on a train axle lathe.
Function's are Traverse left,right motor speed 1000 rpm, Cut motor 
speed 8 rpm and Roll motor speed 5 rpm.


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## varmit (Apr 19, 2009)

Are these actual motor speeds, or machine speeds downstream of gear reducers? If this is a standard 2 HP squirrel cage motor at 5 RPM, it would have very little torque. I am thinking that the drive only controls speed/direction and a PLC or some sort of motion control does the position control via position sensor inputs of some sort. From my vague memory, a SECO drive is nothing special, just a basic VFD. i don't think that it can perform any direct position control, but I am not a wizard on that particular brand. A Pflex 40 does not have encoder feed back as an option anyway.


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## JRaef (Mar 23, 2009)

If it was the old SV3000 Warner / Seco drive, that was a full-on vector drive with an encoder feedback, but it was designed in the days when Sensorless Vector had not yet emerged, so the encoder feedback may have been the only option at the time. The PF40 in *Sensorless* Vector Control is capable of 1% speed regulation over a 60:1 speed range. The SV3000 was capable, with the encoder feedback, of 0.01% speed regulation right down to zero speed. So they are not exactly comparable, *but you have to know what you really need*. 

The PF40 by the way does not have an option for an encoder feedback, so your issue with making the encoder work is moot. You would need to upgrade to a PF70 for that option (or a 750, which has it built-in) if you feel that you need that tight of speed regulation.

It will depend on what you want from the lathe. Having better speed regulation can mean the difference in a near mirror finish cut or one that has visible ridges. if all you want to do is turn down a shaft and you have a gear reduction anyway and all you really care about is maximizing the torque capabilities so that you don't damage cutting tools because the motor began to stall on a deep cut, then the SVC version available in the PF40 may be fine.


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## JRaef (Mar 23, 2009)

Oh wait, you said 40*P*, forgot about that one. Yes it does take an encoder, improves resolution to 0.05%.


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## John Valdes (May 17, 2007)

You had a quadrature encoder to improve speed resolution as JRaef said. Unlike servos that require incremental counting, your encoder was to keep the motor at rated speed regardless of outside influences like load.

The example I like to use is a conveyor belt.
The conveyor belt runs at the predetermined speed with 100 Lb boxes riding on it. Now, someone puts 500 Lb boxes on the conveyor. What happens with a standard VFD? The motor slows down because the VFD is still outputting the exact same volts per hertz for that speed and does not see the load or the speed.
The introduction of the feedback device (encoder/resolver) allows the drive to see the speed and adjust for the increased load. (bigger boxes). Therefore keeping the motor running at the predetermined speed regardless of load.
If your new drive is designed for full torque at zero speed, then it is designed as a torque control and may not require a feedback device. A standard inverter cannot replace a feedback based system and would require a feedback device to operate properly if it does not have the ability stated above in JRaefs post. 
In every case (my opinion) a resolver or encoder is by far the best investment when precise speed regulation is required. However, drives are designed and sold with these high speed resolutions today, that were not available in the past.

Since I am not familiar with your particular drive, as always I would recommend contacting the control manufacturer for expert and spot on advice and technical specs on your application.

The A+ A-/B+ B-/Z+ Z- is a positive and negative pulse in three pairs of square wave outputs completed by a common. 
ZZ, is almost always used as the the check output the drive wants to see to make sure the device is operating (turning).


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## John Valdes (May 17, 2007)

fjl810 said:


> I will be replacing a SECO 2 hp 460 volt ac flux vector drive with most likely an Allen Bradley Power flex 40P.
> The question is the seco drive encoder has A, A- , B , B- and Z, Z-.
> The power flex doesn't have Z terminals, can I use this encoder and not use the Z wiring, or do I need a different encoder or drive.
> Thanks for any help.


Sorry I did not answer your question. Yes. Just disregard them. You can leave the encoder connector at the motor as it is and just don't connect Z+ or Z-. You should ask the manufacturer if the quadrature encoder is okay.


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## RIVETER (Sep 26, 2009)

fjl810 said:


> I will be replacing a SECO 2 hp 460 volt ac flux vector drive with most likely an Allen Bradley Power flex 40P.
> The question is the seco drive encoder has A, A- , B , B- and Z, Z-.
> The power flex doesn't have Z terminals, can I use this encoder and not use the Z wiring, or do I need a different encoder or drive.
> Thanks for any help.


What does "most likely" mean? Is it still up in the air...so to speak?


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## fjl810 (Jul 20, 2011)

The electrical supply that has the contract for are controls is an AB
distributer, It just less paper work if we use AB.


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## MWayne (Nov 8, 2010)

Thanks JRaef and John Valdes, y'all are like two high tech volcanoes spewing forth information instead of lava! I don't know if I will ever have to use encoder feedback but it is good background to have.


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## fjl810 (Jul 20, 2011)

Some Pic's


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## wdestar (Jul 19, 2008)

I'm not going to address your application directly.

As stated, this encoder is a quadrature encoder - which means that it monitors 4 signals:
A
A NOT
B
B NOT

Z and Z NOT are Zero reference marks on the encoder scale or wheel (if rotary) - which, in this case it is.

You stated that you're replacing the drive only - in such a case, Z and Z NOT are not necessary as they apply only to the computer.


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