VFD control using manual inputs

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titan1021

titan1021

Senior Member
Location
Northern California
I've got a client that runs a small organic food processing plant. I've been their Electrician for the past 7yrs and its been interesting and at times challenging since much of the equipment comes from Europe and other various foreign countries. However, they recently purchased a new piece of equipment that will require me to provide and install (3) VFD's. I've installed single VFD's for various machines, but not multiple VFD's for a single large piece of equipment.
I don't normally do much work with VFD's, but what I plan to do is build a cabinet for the VFD's that will have manual inputs on the cover for each VFD, they just need a basic set-up with a stop, start, and speed control for each VFD. They need the ability to adjust each motor individually based on the type of product being run through the machine. Hoping someone knows of a website or other resource that might be helpful in designing the cabinet and some basic wiring diagrams. This is my first time putting something like this together and I would like it to be correct in terms of function and appearance as well. When searching online I just can't seem to find what I'm looking for.

Thanks
 
titan1021

titan1021

Senior Member
Location
Northern California
Jraef

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Just a word of advice though. I always put in an Emergency Stop hard-wired push button on the door or near the machine in plain sight. Having to find and accurately hit the Stop button on a small keypad while someone’s sleeve is caught and pulling their arm into a machine is not going to go as smoothly as you want it to. In most VFDs, all Stop commends are active at the same time so you can have multiple Stop buttons anywhere. Emergency Stop however is often a totally separate function in the drive, meaning it overrides any ramp-down programming etc. you should read and study how that is done in the drives you are planning on using.
 
4-20mA

4-20mA

an analog man in a digital world
Location
Charleston SC
Occupation
Instrumentation & Electrical
Get you a 24x24x8 Hoffman pvc enclosure (or something similar), start and stop buttons, a couple of pilot lights, and build a little control cabinet. If you've done one, you can do three. Depending on which drive you have, you may have to supply control power, but that shouldn't be too difficult to accomplish. The E stops are always a good idea, location depending.
 
Jraef

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Pay attention to mounting details, especially required unobstructed clearances for cooling. Wire duct, despite having slots, is ALWAYS considered an obstruction to proper air flow. So if it says 4” above and below the drive, that means 4” to ANYTHING.

Also, don’t seal them up in the box, they will cook themselves. Lots of air flow through the box; the instruction manual should give you the minimum CFM, and if there is water anywhere near, like at cleaning time in a food facility, don’t do it at all. Use separate NEMA 4X enclosed drives or move the drives out of the wash down areas. Yes, you can use a separate 4X box and add an air conditioner, but the cost is exorbitant in comparison.
 
4-20mA

4-20mA

an analog man in a digital world
Location
Charleston SC
Occupation
Instrumentation & Electrical
Jraef said:
Pay attention to mounting details, especially required unobstructed clearances for cooling. Wire duct, despite having slots, is ALWAYS considered an obstruction to proper air flow. So if it says 4” above and below the drive, that means 4” to ANYTHING.

Also, don’t seal them up in the box, they will cook themselves. Lots of air flow through the box; the instruction manual should give you the minimum CFM, and if there is water anywhere near, like at cleaning time in a food facility, don’t do it at all. Use separate NEMA 4X enclosed drives or move the drives out of the wash down areas. Yes, you can use a separate 4X box and add an air conditioner, but the cost is exorbitant in comparison.
Click to expand...
I was saying utilize the box for the controls, not the drive itself. You make some good points though.
 
P

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Many food processing plants I have been in are not air conditioned and in the summer can be pretty darn warm. Air conditioning of VFD panels is usually a good idea in those cases if you are in a wash down area.

Sometimes you can get by with just putting a stirring fan inside the VFD enclosure. This just circulates air inside the cabinet and eliminates hot spots but also more effectively uses the surface area of the enclosure to dissipate heat.

One thing I have noticed is that for the most part The drives will never generate the worst case heat load The manuals will tell you about. It is very hard to determine what an appropriate size air conditioner is because you don't want it to run and cycle all the time. That's why sometimes I will put two air conditioners in and set one of them at a higher temperature. It's not unusual for the one set at a higher temperature to run very rarely.
 
S

SeanOliver

Member
Location
New Bern NC
Occupation
Wholesale Electrical Distribution Account Manager
I suggest you make friends with a local automation distributor. Most have Industrial Control Specialist and VFD specialist whose primary job is to support licensed professionals with the application of their products. Theres a lot of considerations to be made when installing vfd's. I'll just mention 1 because it seems to happen a lot in my neck of the woods. Safety disconnects at the motors with a vfd up stream. If you kill power between the motor and the vfd, before stopping the vfd, you have a 25% shot at letting all the smoke out of the vfd. You need special aux contact on the safety switch that opens a split second before the safety switch clears. That signal removes the enable to the vfd and the vfd immediately goes into whatever mode you program it to stop. You can remove power on the line side of a vfd abruptly without to much trouble but it is still recommended to have a controlled stop. Drives like controlled stops and starts.
 
J

JimInPB

Member
Location
South Florida
Occupation
Engineer
For manual controls, I like standard start/stop boxes and a potentiometer. You can buy potentiomentrs these days that are in housings that fit standard 22mm push button holes. The earlier recommendation of an e-stop switch is a good idea. Depending on the application, I may wire that to a fast stop input that uses a brake resistor or a free wheel input on the drive. If it is going to kill big power directly, I would typically kill the mains, but different projects have different requirements.

Putting multiple drives in a single machine us USUALLY not a problem, but I have had issues over the years. One was in an elevator bank in an old folks home in NY about 30 years ago. The other was in a large piece of automated machinery in PA about 15 years ago. In both instances, adding a new drive to the system caused a preexisting drive to malfunction. In both cases, line reactors & filters were able to solve the issues. In Europe, those sorts of devices are required as standard. Here in the states, they are optional, or at least they were the last time I checked. I'm a little out of date on those rules now.

If the machine operators don't like the noise that the drive motor makes, look up the carrier frequency parameter & set it up around 30khz. Only dogs will be bothered by it after that. This does beat on the motor a little bit, but not a lot.

When enclosing a drive, heat dissipation is a consideration. Some drives that are designed to be enclosed, like Danfoss, have heat sinks that you can mount to the back of a metal enclosure. You can actually buy enclosed drives from them too, or at least you used to be able to. I assume that they still offer that.

I would try to get drives that have inputs for standard NO start & NC stop buttons as well as a 0-10vdc speed control signal. Not all smaller drives have these options anymore, but most do. Some have all NO inputs for switching. Some have 0-5v speed inputs. Some have -5-+5vdc bidirectional speed control. Some have 4-20ma speed control. Some of the expensive ones have fiber optic links or talk on control busses like Profibuss, canbuss, device net, etc., but that is probably not what you want here.

If we are talking 3 phase power and 3 phase motors, then UVW is normally power in & RST is normally power to the motor. The control terminals will be different on different drives. Typically you have a common, and some digital inputs. You usually also have some sort of analog speed control and a dry contact output or two. You may have frequency out & other fancy stuff. You may have preset speed selector inputs. Different drives have different features. Some accept single phase in & put 3 phase out. There are lots of options.

Some drives have start, stop & speed control on the front of the drive. You can sometimes mount the drive in a cabinet with a cut out that allows access to the controls on the front of the drive. Some drives have remote keypads available, but those are usually not the really cheap ones.

If you need precise speed control under varying loads, there are vector drives or servos.

I would need to know more about your actual application to recommend a specific drive.
 
kwired

kwired

Electron manager
Location
NE Nebraska
SeanOliver said:
I suggest you make friends with a local automation distributor. Most have Industrial Control Specialist and VFD specialist whose primary job is to support licensed professionals with the application of their products. Theres a lot of considerations to be made when installing vfd's. I'll just mention 1 because it seems to happen a lot in my neck of the woods. Safety disconnects at the motors with a vfd up stream. If you kill power between the motor and the vfd, before stopping the vfd, you have a 25% shot at letting all the smoke out of the vfd. You need special aux contact on the safety switch that opens a split second before the safety switch clears. That signal removes the enable to the vfd and the vfd immediately goes into whatever mode you program it to stop. You can remove power on the line side of a vfd abruptly without to much trouble but it is still recommended to have a controlled stop. Drives like controlled stops and starts.
Click to expand...
If it is programmed to ramp to a stop, it will very likely still be ramping when the power poles open.
 
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