Thread: Speed control alternative to VFD??

Everyone has to decide on his own, if he has the know-how and the skills to install his own VFD in a safe manner. A good help in making this decision are the very detailed installation manuals, that come with every good VFD. In any doubt, let a sparky do the job.
If you still want to go ahead, I will try to address some concerns voiced in this thread.

- VFD's must always be installed in an appropriate enclosure. The only exception are IP rated VFD's, which already come installed in a factory enclosure. This in an example how these typically look like:
kbac_1.jpg
- you are free to choose if the VFD output to the motor is directly hard-wired, or if connectors are used. If you use connectors, you must ensure these are approved for the voltage used.
- The VFD installation manual usually include tables to determine the proper wire diameter, depending on distance between motor and VFD and VFD power rating.
- the connectors I proposed (type C16-1 4-pole) are used by Australian industry for 240V mains applications. I am aware of Davey having used this connector between pump motor and Hydrascan pressure unit. Purpose being to make the pressure unit user replaceable. These pumps were mass produced and even exported. On the picture you see the connector in front of the yellow motor housing.

The connector however bears no markings to any Australian standard or test regime. This is not necssary, because Australia recognizes by reciprocity test regimes carried out by other testing agencies such as UL, CSA, VDE etc etc.
The pump as a whole unit would however have been electrically tested in Australia before production began. There is no reason for anybody to claim these connectors were not fit and safe to hookup a motor to a small HP 240V VFD.
- in doubt, have a sparky inspect your work before turning it on.
- there is absolutely no reason, why a homemade one-off VFD installation should not at a later stage be sold with the machine, provided it is safe in every respect and properly executed. There is no law requiring that a one off appliance to be subjected to an expensive test regime. This is only necessary if a batch of identical units is to be produced for sale.

Lets address a couple of issues.

Firtsly it is beyond the scope of an online forum to mount a comprehensive discussion of relative compliance and safety issues regarding the installation of electrical items on machines.

The issues directly addressed in Australian standards and the legeslation that mandate them are extensive.

It must be understood that the requirements are context sensitive..in that factors of how the installation is built and intended to be used and how the equipment is constructed determines how other things shall be done and what shall be used to do it.

There is a great deal of difference in what is allowed inside a piece of equipment within the non-user accessable enclosure and that allowed outside.
There are whole swathes of mandatory requirements that apply when parts are "user accessable".....however when they are permanently enclosed and not user accessable they are either specifically exempt or do not apply.

There is also in recent versions of the standards some very specific exemptions for use of parts and methods that would not be otherwise permitted in equipment that is specifcally engineered and approved.

Just because you see a particular item as part of a genuinely approved item..it does not mean that that item is appropriate or permitted for general use or in another application that has not specifcally been approved.

IF an item is a "prescribed item".....that means most things like general use electrical plugs and switch gear, flexible cables and a great many other things...it most definitely requires to carry an australian approval marking and probably and Australian Standards mark.

There may be some acceptance of overseas compliance....but it is not universal and it most certainly does not apply to a great many mandated items and applications.


In the case of the connectors inside a washing machine or any other machine for that matter...they are inside the machine, not user accessable and under a whole other range of requirements...they are in general NOT..."prescribed items" and do not require any australian approval.

As for the plug used on the davey pump......if it is user accessable and yet bears no australian approvals marking...as far as I understand they only way that that can be so is that, it was individually approved as part of a specifically approved and engeieered item.

All the above said too....there is a great deal of electrical equipment and items that are on sale but simply do not comply with the letter and the intent of the regulatory scheme....some of it not even close....when we are seeing multiple recalls on electrical items because they are "dangerous" or "non-compliant" you don't have to look far to see this is true.

How about that company that was importing and selling cable, that was outright dangerous and nothing like compliant.....big news in the electrical industy in the last month or so......a couple of chains that stocked this cable are looking down the barrel of a very large bill...the importer declared bankruptcy.

This is because we have not had a comprehensive mandated electrical testing and inspection system in Australia......( serioulsy don't get me started on this one...be warned Don't)


All too often plenty of people including those who should know better try to argue that this or that electrical rule or standard does not apply to them or their situation.....well the latest versions of the standards reflect that.......there are plenty of clauses and explanatory notes saying....."OH no you can't"..and ..."Nice try chum".

Now because VFDs are an industrial item...and not switchgear, connectors or cable.....my understanding is they are not prescibed items...thus do not require electrical approval...even though they are required to be constructed in accordance with Australian standards..

BUT..they are most definitely captured under the "electromagnetic compatability framwork"

SO.....that VFD..does it have a "C tick" mark.

As far as that "home made" VFD installation on a piece of equipment being sold.....

OK lets call a spade a spade.......unless you are an electrician or other licenced electrical worker..its been constructed illegally.......unless you have a pretty good knoweledge of at least AS3000 and AS3100......its probably not compliant.

After it was constructed and before it was connected to power for the first time, it should have been examined and tested according to the regulatons and standards to ensure it was safe and compliant.......AND....at least in some states a " certificate of test" ( or in NZ a warrant of fitness) issued.

Before the item is sold or passed onto another owner.....the item should be examined and tested according to the regulations and standards and a " certificate of test" issued OR a notice attached in the prescribed form stating that the item has not been tested and may not be electrically safe.

I don't know about interstate...but in QLD...any person that sells an item that later proves to be non-compliant or unsafe is liable for large fines and civil damages.

Serioulsy chaps.....think long and hard before youn play with this stuff.

cheers

Lots of interesting discussion and debate here. So I'll bring up another point……..What do you guys do about an enclosure? In my case I am running a belt grinder so lots of dust, and there will be water used to keep the steel cool.

If I use the kindly donated motor 2hp 2 pole 3 phase motor here wired in double star and combine that with this 3HP 2.2KW 10A 220-250V VFD DRIVE INVERTER CONTROL as suggested (http://www.ebay.com.au/itm/3HP-2-2KW...item1c3984881e)

What do I do next, as the VFD in this case will be used to operate the grinder as a user control. Fitting it to a box on the wall isn't the best option, having it within reach of the operator probably is. From my limited understanding the enclosure needs to be 4X the size of the VFD and have fans and filters fitted. This seems quite unwieldy in this application.
DSC_0005-16.jpgDSC_0023.jpgDSC_0042.jpggrinder3sml1.JPGIMG_2081.jpgshop.jpgSKAULky.jpgwglMhgJ.jpg

Remote???
May 5 2013 2 X 60 Grinder 016.jpgMay 30 stills 001.jpg


Are the IP rated VFD's, which already come installed in a factory enclosure much more expensive and harder to come by???
Grinder-3.jpgGrinder-2.jpgknives_random_034.jpgIMG_0447.jpg




Back to the motor will this motor be able to utilise the 2x feature of a VFD for double speed?

3 phase (Inverter Duty) motor would have to be capable of running at 120 HZ to utilize the 2X function. I personally have never seen a 3 phase motor that had 120 HZ on the name plate.

This is the one that seems to be popular with the 2x72" belt grinder manufacturers
http://www.walkerindustrial.com/KB-E...-gray-gfci.htm
KBAC-29 (1P) (GRY) GFCI - KB Electronics AC NEMA-4X Hybrid Inverter, 230 VAC 1p In, thru 3.0 HP, 230 VAC 3p Out w/GFCI software (10011)
$378USD + Delivery is there a cheaper equivalent??

looking at the pictures posted, most og the VFDs pictured would appear to be IP rated......the types of boxes, the rubber booted switches and the glands for cable entries are good indicators.

Where you got this 4 times the size of the VFD..I'm not sure.

The issue you have is VFD designed for particular uses......if its a box with internal heatsinks and fans blowing in and out it is obviulsy a piece of electronics designed to be housed in clean dry air.
In a lot of undustrial process control the controll gear is housed in cabinets or in rooms that are controlled environments ( providing cool dry filtered air) and quite some way from the loads they are controlling.

you arely need to be looking for units built like the ones pictured.

The other option is that some VFDs and other controll gear have extended controlls via simple contact closures or rotary controlls..or complete dedicated remote controlls

hounsing u a unit like this... http://www.ebay.com.au/itm/3HP-2-2KW...3D121224071198
to be in an IP rated situation is pretty much a fools erand.

cheers

Hi Dale,

A couple of things.. first the enclosure doesn't have to be 4 times the vfd size and forced air cooling.. where did you hear that? if you look at boxes like the Teco pre-packaged vfd, they just put the heatsink outside the enclosure.

This one has some the things I would be looking for... estop, easy access to controls, ( I'd like to see how that door seals, the hinge looks a bit agricultural.. ) I like the anaconda armoured cable to motor, with proper glands.

Change the box for a better quality enclosure and this would be a good starting point.



Ray

The KBAC 24D is for 1 hp and less with either 115 or 230v single phase in and 230v 3 phase out to the motor. We typically use this VFD with the disk grinders and for this use a forward/reverse switch is needed and is available for $35.00.
The KBAC 27D is for 1.5 or 2 hp motors. with either 115 or 230v single phase in and 230v 3 phase out to the motor.
The KBAC 29 is for 3 hp motors with 230v single phase power in and 230 3 phase out to the motor.
These are NEMA 4X (washdown, dust proof) enclosed VFDs. These are very simple systems to set up, no programming, I had only 3 jumpers to change on the KBAC 27D. I have a hard time believing how easy this new design, direct drive grinder was to build and then to set up the VFD.



In comparing USA built systems and motor speed we are running slower RPM due to a base factor of 50Hz vs 60Hz. So a USA Spec 3600RPM motor is a 3000RPM motor here which under load at 50Hz is a 2850 RPM which is what is usually show on the motor plate in Australia. I am I on the right track here?

Approximate Electrical Motor Speed (RPM)
No. Poles	Speed with Rated Load		Synchronous Speed (no Load)
60 hz	50 hz	60 hz	50 hz
2 Pole	3450	2850	3600	3000
4 Pole	1725	1425	1800	1500
6 Pole	1140	950	1200	1000
8 Pole	850	700	900	750

The VFD you are proposing has open cooling slots. It is intended to be installed in an enclosure. Especially in your case, where metal dust, cooling water and chips are to be expected. Metal dust on the circuit board is bad news, so are metal chhips falling through the cooling slots in the VFD. Not to mention the water... So we probably all can agree, it needs be enclosed.

The encloseure CAN be vented but does not have to. Good brand name VFD's come with an extensive installation manual. The manual will tell you exactly what the minimum dimensions for an enclosure must be. The dimensions for a non vented enclosure are always much bigger. The bigger surface area of the enclosure is required to ensure cooling by convection alone is going to be sufficient. You need to consider how hot your workshop can be in a hot summer day, and add to it a temperature rise inside the cabinet. You normally have to derate your VFD fer by 1%, for every degree that the ambient temperature inside your enclosure exceeds 30C. This is all well explained in installation manuals. The problem is that the low cost Chinese VFD that you are proposing, may not come with much of an installation manual. But you may look at installation manuals from brand name VFD's od same design/size/power as a guideline.

The enclosure may be wall mounted, or free standing. Or you may choose to integrate it, for example in a lathe's or mill's metal cabinet. In any case you have to assess the specific situation, there is no "one fits all" solution.

The examples you show in the pics use IP rated VFD's. These cost usually twice as much as bare VFD's, because the supplier provides you with a VFD pre-installed in an enclosure, with all switch gear integrated. Its also safety tested and approved. If you can afford it, that is the quickest and safest solution. However, I like to have direction and speed control integrated in my machine, for example on top of the headstock od a lathe, such as I can control it with my fingetrips at any time. This requires a remote control box to be made. Sure, if you can afford it you can buy this too, either from a VFD maker itself or from companies that supply "drop-in" VFD solutions for machine tools. Fact is that if you are a hobby user, you probably cannot afford to buy ready made solutions.

> Back to the motor will this motor be able to utilise the 2x feature of a VFD for double speed?

That depends on the motor. If it is a 2 pole motor, it would exceed the safe rotor rpm at 100Hz. It it is 4 poles or higher there should be no problem for the motor. However, you still need to make sure the driven machine is safely capable of 2x the speed. For example, spinning a grinding wheel at 2x its rated speed may be "criminally negligent" and asking for a bad accident.

The KABAC vfd you mention is a nice drop-in solution for your problem. The price appears very fair. But make sure it is for a 240V model.

The 4 Times the size of the VFD for adequate cooling etc, was picked up in existing discussions on other forums re the what enclosures are required, i.e. practical mach. It seemed to be a general consensus and stated to be in the VFD instructions.

Originally Posted by cba_melbourne

> Back to the motor will this motor be able to utilise the 2x feature of a VFD for double speed?

That depends on the motor. If it is a 2 pole motor, it would exceed the safe rotor rpm at 100Hz. It it is 4 poles or higher there should be no problem for the motor. However, you still need to make sure the driven machine is safely capable of 2x the speed. For example, spinning a grinding wheel at 2x its rated speed may be "criminally negligent" and asking for a bad accident.

The KABAC vfd you mention is a nice drop-in solution for your problem. The price appears very fair. But make sure it is for a 240V model.

I was told it is a 2 pole motor. What would the max HZ and RPM be at the shaft or it is a nominal drive wheel size assumed?

If I add a 4",5", 6" Drive wheel to this will I be increasing the RPM from 4" to 5" by 25% and 4" to 6" by 50% As circumference is directly proportional to diameter, because the circumference C is proportional to diameter d. Pi = C / d = constant. C = pi × d d = C /pi 2 d = 2 C / pi

A 2 pole motor will spin at approx. 2800rpm at 50 Hz. Or about 5600rpm at 100Hz. It may top out at around 7000rpm and 150Hz. You must program your VFD such as to limit its max. frequency to a safe value.

But wat is safe? The rotor will probably not disintegrate at 7000rpm, nor will its bearings instantly fail. But the rotor was not balanced for such speeds, and it was not designed for such centrifugal forces. It could fail and it would be pilot error if it did. Likewise the grease filled bearings would soon overheat and life span reduced to days instead of years. A stock standard small hp 2pole motor should probably be safe for up to 4000rpm, anything much above is taking a risk.

The top safe speed of the driven machine only you can assess.

Originally Posted by BobL

It not only has to be ∆, is has to be 240V ∆, if its 415V ∆ it will only generate ~ half power on 240v.

BobL,

Can you explain the difference between 240V ∆ and 415V ∆? Are you talking about different motors or are you talking about different connections for the motor windings?

Grant

Originally Posted by grunto

BobL,

Can you explain the difference between 240V ∆ and 415V ∆? Are you talking about different motors or are you talking about different connections for the motor windings?

Grant

The motor nameplate will usually say on it what the voltages and connectivities are
For motors that can be reconfigured the typical labels used are " 240V ∆ / 415V Y" or "240/415 ∆/Y" - this means the motor can be reconfigured at the Connection box to suit 240 or 400V.

It's not usually to see 240/415V ∆/∆ or 240/415 Y/Y.

If a nameplate just has one Voltage e.g. 440V and no info about connectivity then it could be either a ∆ or a Y connection (my "limited" experience is that they are usually Y on smaller motors) and they cannot usually be switched between connection modes at the connection box and the motor will need internal modification if you want to run it at a different V - motor rewind people can do this.

I've only ever run this motor to 60hz, no higher. Not to say that it couldn't go higher.
Most commercial grinders seem to use a 5" drive wheel and a 2 pole motor. The radius master uses a 4 pole motor and an 8" (soon to be 9") drive wheel.

Ew

Originally Posted by soundman

Lets address a couple of issues............

So you say that connector is perfectly safe to use by Davey, despite lacking any Australian approval mark, despite being user accessible, despite being used in wet areas, just because Davey paid some $10k to have it "individually approved as part of a specifically approved and engeieered item". Yet if I use exactly the same connector for my workshop VFD it is suddenly not safe anymore, despite bearing the UL and CSA and VDE approval, just because I did not spend $10k too to have it "individually approved as part of....". I am not sure your interpretation of the standards really reflects the intentions of the regulator body.

This would affect every component, switches, pushbuttons, fuseholders, terminasl blocks, wires.... All would have to bear the Australian approval mark. The selection of such components with AU approval mark is very limited, and what there is is generally overpriced, often obsolete and oversized for the task. That is just not acceptable in todays global world. It is reminiscent of the days when you had to call the electrician to swap a light bulb in an office. Of days when safety standards were abused to shield local makers from international competition.

Nowdays consumers do buy electrical appliances from all around the world. Nobody can force them to pay through the nose for AU approved computers, printers, wall wart power supplies, shavers etc etc etc. Australian consumers just order from eBay if the price difference exceeds a certain pain threshold. The regulators know that, and that is why standards are being harmonized around the world. Australia is now officially a 230V country, and that opens the doors for imports of electrical appliances from many countries. Yes, this means to some extent it is now up to consumers to make sure there appliances are reasonably safe. This does not only apply to private direct imports. Do you really think every China made lathe or mill sold by small dealers in Australia bear one single Austalian approval mark? They may bear a CE mark, but are you sure its not a fake mark? Have you looked at the switchgear or wires that they use, would you deem that stuff safe? Sure, you may sue the dealer for selling unapproved electrical goods - so what, those are one man businesses, they fold and two others open shop with the same merchandise.

What do you say about Chinese VFD's from Ebay? They do not bear any Australian approval mark. Why should any user of such VFD insist on using switchgear or connectors with Australian approval mark? Besides, I use VFD's from Siemens and Telemechanique and Omron and Yaskawa..... and none of them displays an Australian approval Mark either. So they must be unsafe to use? Come on....