# Power Flex 70



## 360max (Jun 10, 2011)

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/20a-um001_-en-p.pdf

page 135


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## JRaef (Mar 23, 2009)

I'm frankly embarrassed that you got someone in tech support that could not answer this question. Was this Rockwell tech support?

So that you know for the future, ALL modern PWM drives work basically the same way. The incoming line is just rectified to DC, so swapping phases on the incoming side does absolutely nothing as far as the drive is concerned. Had you swapped the output leads, the motor would have reversed.

But there was no need. All PWM drives are also capable of running a motor in either direction. The Drive takes the DC and electronically recreates a type of AC for the motor; it's called "inverting", hence the alternate name "inverter" for the drive. In that process, the electronics can recreate the AC in any phase relationship, it's just about how it fires the transistors. So you can tell the drive to fire A-B-C or A-C-B, it's all the same to it. You can simply set up an input command to the drive to tell it to do that whenever you want, or you can do it from the keypad. That's what that instruction manual will tell you.


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## glen1971 (Oct 10, 2012)

JRaef said:


> I'm frankly embarrassed that you got someone in tech support that could not answer this question. Was this Rockwell tech support?


After I called Rockwell one night for VFD supprt and they asked for my customer service contract number, and I explained that I was a service company and didn't own any drives but repaired them, they told me that for a mere $750 bill on my credit card I could talk to someone and they might be able to help me.. After about 10 minutes of discussing this further and that I was not going to pay it, the person on the other end said "Sorry I can't help you further." I said (in a rather uncalm tone) "No.. I'm sorry.. I don't own any, but I sure sell a fair amount and this lack of service will definately impact my future drive recommendations to my clients." and I hung up.. Troubleshot it and managed to get them back up and running (someone had messed with a couple of the parameters that were the obscure ones)... The next morning, I got a phone call from the Regional Service Manager for Rockwell over my "service experience" the previous night (apparently he heard a recording of my call). I explained the situation to him and he said "Of course you don't own any drives, but we appreciate your business. This problem won't happen again." He apologized and I assume corrected the problem.. I haven't had to call for support for sometime though, but I guess we'll see next time..


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## Jabberwoky (Sep 2, 2012)

JRaef said:


> So that you know for the future, ALL modern PWM drives work basically the same way. The incoming line is just rectified to DC, so swapping phases on the incoming side does absolutely nothing as far as the drive is concerned. Had you swapped the output leads, the motor would have reversed.


I'd like add a small caveat to swapping motor leads in PWM drives. If it uses encoder feedback (Vector drive) then just swapping the motor leads alone may not work. It could cause runaway that may damage equipment depending on the application. In some drives the feedback reversal is sensed and adjusted automatically without a problem. I have personally run into a few that require a parameter change.


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## JRaef (Mar 23, 2009)

Jabberwoky said:


> I'd like add a small caveat to swapping motor leads in PWM drives. If it uses encoder feedback (Vector drive) then just swapping the motor leads alone may not work. It could cause runaway that may damage equipment depending on the application. In some drives the feedback reversal is sensed and adjusted automatically without a problem. I have personally run into a few that require a parameter change.


OK, true for the small minority of full vector drive applications where there is an encoder feedback. Chances are about 99.99999% that a screw conveyor was NOT one of those. 

I wasn't actually promoting it because *swapping leads on a VFD fed motor is completely pointless*. I was just trying to get him to understand why swapping the leads on the line side would NOT result in the motor changing direction, but swapping them on the load side would have.


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## pudge565 (Dec 8, 2007)

JRaef said:


> I'm frankly embarrassed that you got someone in tech support that could not answer this question. Was this Rockwell tech support?
> 
> So that you know for the future, ALL modern PWM drives work basically the same way. The incoming line is just rectified to DC, so swapping phases on the incoming side does absolutely nothing as far as the drive is concerned. Had you swapped the output leads, the motor would have reversed.
> 
> But there was no need. All PWM drives are also capable of running a motor in either direction. The Drive takes the DC and electronically recreates a type of AC for the motor; it's called "inverting", hence the alternate name "inverter" for the drive. In that process, the electronics can recreate the AC in any phase relationship, it's just about how it fires the transistors. So you can tell the drive to fire A-B-C or A-C-B, it's all the same to it. You can simply set up an input command to the drive to tell it to do that whenever you want, or you can do it from the keypad. That's what that instruction manual will tell you.


He probably could have but I could barely understand anything he said and he was not understanding my question. Later in the evening a different screw conveyor needed to be reversed I just swapped at the disco right before the motor. I asked the techs at the shop, there is a button on the drive to reverse it but it may or may not be disabled in the parameters.


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## Peewee0413 (Oct 18, 2012)

Takes the same time to enable the reverse in the VFD as it does to swap the leads.


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