# Controlling direction on VFD



## IMM_Doctor (Mar 24, 2009)

*Are you sure?*

I would NOT do it that way, as a loss of analog control (0v) will cause the VFD to run the motor.

Most VFD's have a single digital input via hardwire, or over controls communication network to cause alternate rotation.

With the Direction Bit Off, the motor will be commanded to 0-100% in one direction based on the uni-polar 0-10vdc analog input command.

With the Direction Bit ON, the motor will be commanded to 0-100% in the ALTERNATE direction based on the same uni-polar 0-10vdc analog input command.

Also suggest you post this same query on PLCS.NET forum.


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## sparkie (Apr 2, 2008)

I agree that this is an inherently bad idea -you want a system that will fail safe . can you explain the system you are building.

For simple things you can use relays to switch inputs providing you have a safe method of enable and stop. 

For bigger things a PLC can be programmed just about as far as you can imagine.

what ever your method it should be interlocked so one fault can't cause unexpected operation.


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## Ferrari_man (May 13, 2009)

IMM_Doctor said:


> Most VFD's have a single digital input via hardwire, or over controls communication network to cause alternate rotation.
> 
> With the Direction Bit Off, the motor will be commanded to 0-100% in one direction based on the uni-polar 0-10vdc analog input command.
> 
> With the Direction Bit ON, the motor will be commanded to 0-100% in the ALTERNATE direction based on the same uni-polar 0-10vdc analog input command.


I understand there is a risk if I lose my analog signal but in this case it wont be dangerous other anything.

If I understand you right there is a funktion in some VFD's which enables you to run from -10 to + 10v and 0 V being stop?

If yes, can you point me in a direction to finding a brand which is able to do it. I have some cheap T-verters but I don't think they can.


Ferrari_man


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## John Valdes (May 17, 2007)

Try these out. Ask for the drives specialist about your questions, then get him to recommend a distributor in your area.

www.baldor.com
www.wegelectric.com
www.automationdirect.com
www.tecowestinghouse.com
www.yaskawa.com


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## Ferrari_man (May 13, 2009)

Hello again.
I have tried to write to some of these companies but havent got some real answers.

But I was thinking about if it is possibly to control the VFD with -10V to +10V, which I also have available.

So it would be 
-10V full speed reverse (and -5V is 50%)
+10V full speed forward (and +5V is 50%)
0V stop.

We have a lot of teco t-verter E2 series, so if they were able to do it, it would be great.

hoping for a reply

Ferrari_man


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## PLCMentor.com (Apr 15, 2009)

Ferrari,
I cant see anything good coming out of how you want to control your drive. I dont think an AC inverter is going to do that just for the simple reason that there would be a complete loss of torque at the low ranges. Used to be you would never operate an AC drive reliably below 10%. Now with todays vector drives and with encoder feedback you can get down pretty low, but I would never want the drive active and the motor stopped like you would have at the lower ranges. As IMM mentioned, you can use a direction bit. There may be DC drives that can do that and I have worked with hydraulic drive systems that work that way where you are actually controlling a modulating hydrdaulic valve. Maybe you should post more about what you are wanting to achieve and we could help with that instead of getting stuck on this idea of +/- fwd/rev control. 

Russell


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## 5volts (Jan 11, 2008)

Ferrari_man said:


> Hello again.
> *I have tried to write to some of these companies but havent got some real answers.*
> 
> But I was thinking about if it is possibly to control the VFD with -10V to +10V, which I also have available.
> ...


 









No, no, no, no! Instead of trying to re-invent the wheel you should wire/configue the drive in a standard form.


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## John Valdes (May 17, 2007)

Ferrari_man said:


> Hello again.
> I have tried to write to some of these companies but havent got some real answers.
> 
> But I was thinking about if it is possibly to control the VFD with -10V to +10V, which I also have available.
> ...


You can do it. Any decent VFD can perform this simple operation. Programmed properly it will do as you wish. I have some background with TECO. I do not remember if this series control has the functions you need. I can bet you will need a feed back device like an encoder. The drive has to know the direction the motor is in. And you need to program the drive to recognize direction in relation to the speed reference (analog signal).

Call TECO technical support at 512-218-7536. Ask for Bill Downs, Mike Cook or Dan Wolf.

I have not been in touch with these guys for a few years. You might be able to find at least one of them. If not ask for the drives specialist.
But you can do this. I have seen it done many times and have installed several drives using the reference voltage to determine direction and speed.

Just in case try these guys. 

Baldor: Jeff Lovelace (479-649-5247) or Tommy Taylor (479-648-5704)
Weg Electric: (800-839-2529) Ask for the drives specialist.
ABB: Kathy Holmes (262-785-8538) Steve Weingarth (262-785-3200) or drives specialist.

Again. If you cannot locate these folks, ask for the drives specialist. I am retired now for almost five years.


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## 5volts (Jan 11, 2008)

John Valdes said:


> Any decent VFD can perform *this* simple operation.


I disagree.



John Valdes said:


> I can bet you will need a feed back device like an encoder. The drive has to know the direction the motor is in. And you need to program the drive to recognize direction in relation to the speed reference (analog signal).


This no longer becomes a simple operation.

If money is not a issue hook up a drive with a communication module and do everything in the PLC. Such as start, stop, jog, direction, speed, etc... 

A lot of things can be done but when installing you should consider reliability, safety, and money. Why not just KISS.



Ferrari_man said:


> So it would be
> -10V full speed reverse (and -5V is 50%)
> +10V full speed forward (and +5V is 50%)
> 0V stop.


I see a lot of VFD faults and I hope you plan on using gold contacts.


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## John Valdes (May 17, 2007)

I agree the PLC should be the master of this operation. But the logic is available on the drives themselves. ABB has a control with a PLC on board. All I am trying to say is "he can do it this way". But then he could do it any number of ways. AC drives have become so smart and they can do so many things. Why not take advantage of these capabilities. But your point is well taken.


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## lukejenson (Sep 14, 2009)

How did it turn out?

http://www.clrwtr.com/ABB-Drives.htm

This is my abb drives distributor. Give them a call if you still have questions. They've been very helpful to me in the past.


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## smeric28 (Nov 16, 2009)

Ferrari_man said:


> Hey..
> 
> I have a 0 to 10 V signal from a device which I would to control a VFD with. The problem is that I need it to work like this.
> 
> ...


Delta VFD-E can do this it has an onboard plc and like almost all vfd's an analog input. so you can do whatever you like  plus the software is free check out www.delta.com.tw look in the industral automation section.

forget about abb and allen bradley == $$$$$$$$$$$$$$$$$ Big Bucks


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