Danfoss VFD

[LJM]

Hi,

Does anybody have experience of the Danfoss VFDs? I’ve seen a number of comments about the ease of use and standards of documentation of VFDs, many of which seem poor; the Danfoss units come up reasonably regularly, so I’m hoping they‘re amongst the better options.

Also, should I aim for one with the same rating as my motor (3kw) or higher?

Thanks very much

 

[Myfordman]

No harm in having slightly higher power inverter provided you programme the power down to match the motor to ensure it is adequately protected. But there is no real advantage to having a higher power inverter either.
I think I’ve used a danfoss in the past without problems.
Get hold of a manual first and see how readable it is maybe?

 

[LJM]

Yeah, getting the manual would be a smart move. I’m looking at one that’s described as an HVAC drive; is one VFD much like another, for our purposes?

 

[Ttrees]

Yeah, getting the manual would be a smart move. I’m looking at one that’s described as an HVAC drive; is one VFD much like another, for our purposes?

Myfordman (Bob) has written an extensive article on VFD's which will likely answer the questions you have.
Induction motor information here https://drive.google.com/file/d/0B_GZrXNsNxTlQzd6aldlQjJtUDQ/view?usp=sharing

What are you planning on running?

I use cheap ones for a TS and bandsaw.
Some of the fancier ones offer more protection for the motor and the VFD
These things don't like it if the motor bogs down, I learned that the hard way, by being a numpty using a damaged blade.
Luckily my motor was alright, got too hot though, could smell it!
I bought another hundred quid one and was sorted.
I won't be taking the peas again like that.


Some VFD's have parts so you can use a braking resistor for emergency stops.
Some are more suited for spindle work and have all sorts of options, ports, and a big list of parameters for controls by computer.

Some have a fan that runs constantly, although you (probably) could modify any of them
to "shut up" with a little temperature activated switch.
Nice to have on a bandsaw that's plugged in a lot of the time.



3 wire control, (separate start and stop switch) and the cheapo units.

A while back I helping another fella (and myself) with a Far Eastern unit for a TS
He had a similar issue with his start and stop, like I had...
(I just swapped the front panel with the old one on mine)

Seems like a few of the ports for the switches can be faulty.
I was informed on SMC that you can allocate/change a function of these ports
if you wanted emergency stop (if your VFD actually had the components inside for it to work)
Or in this case, changing the function of one of them, so three wire control is possible.
(which is a much safer than a simple toggle switch, i.e "two wire control")
You can do things like make a kick paddle

That could be any of the three little micro ports for a separate start and stop button.
Which would be your start (FOR) which goes into a common (labeled RST on my VFD)
and from that to the stop (DCM)

I couldn't get three wire control to work with the new one, but I have yet to try seeing if I could have a go allocating functions to the ports.
There are much less ports on the new one, and I'm not even sure if it has those parameters available.

This noisy Huanyang was put on the tablesaw, and has a nice eerie hum to it.
The replacement I've hooked up a toggle switch to instead, but I've kept the emergency stops.
This isn't good practice, deffo confusing for someone else not aware!
as I can start the machine by de-latching the push button, as the manual start is always flipped on...
I like having the button under the big table, so got used to using it.

One more thing to beware of is that some sellers are passing off micro sized units with photos of the regular sized units.
I can't imagine them working TBH, how teeny they are.
Get dimensions first, before buying if choosing these.


And lastly be aware that these hold a lethal charge well after being unplugged
Wait until all the juice has drained from the caps before going near those main
input/output terminals, that could take some time.

And make sure that you understand parameters before hitting start.
Many of these are factory preset for high speed spindles which would cook your induction motor.

Bob's write up will answer all about parameters.
the best read up I've ever came across, thanks to him it has opened up a world of machines, which wouldn't be feesable for me otherwise.

Just my 2 cents on the cheap options.
All the best

Tom

 

[LJM]

Cheers Tom,

that’s good info. Unfortunately the linked file never opens for me.

Initially I’m fitting one to a table saw; if possible, I’d like to have it set up much as the machine came out of the shop, that is, with a two button on-off and a kick-stop.

 

[Ttrees]

If you go to Bob's "the other place", you will likely find a PDF version of it to download instead.
I'll try again
https://drive.google.com/file/d/1dBTVXxPUa4dTeCREIph-c0I4X8fdzdtS/view

 

[Spectric]

You will need an invertor capable of providing more than the motors full load current based on the fact the output is now three phases so the square root of 3 which is 1.732. Ie motor requires 6 amps then the invertor must be capable of supplying 10 amps. Never used Danfoss VSD's but their heating controllers do not compare to Honeywell, and VSD brands that spring to mind are Siemens, ABB, Hitachi and mitsubishi for general use but had a preference for ABB on heavy applications where something like the ACS580 was great upto 500Kw loads.

Hitach blurb recomends an even larger VSD quote

"The rule of thumb Hitachi recommends is to start with the 3-phase motor’s nameplate full load amperage (FLA) rating and double it. Then select an inverter with this doubled continuous current rating. This will give adequate margin in the input rectifier bridge and bus capacitors to provide reliable performance. NOTE: Fusing or Circuit Breakers should be sized to match the INVERTER input current rating, NOT the motor current rating!"

 

[LJM]

Thanks for the input Spectric, I’ll definitely refer back to that when making my selection

 

[LJM]

If you go to Bob's "the other place", you will likely find a PDF version of it to download instead.
I'll try again
https://drive.google.com/file/d/1dBTVXxPUa4dTeCREIph-c0I4X8fdzdtS/view

Thanks Tom, got the file this time! Looks like some good bedtime reading...

 

[Spectric]

Hi

Yes a lot of people want to run 400 volt three phase motors from single phase 230 volts but it is ironic that when you have a true three phase supply at 400 volts it is now more common in certain applications to configure the motor as a Delta configuration (230v)and set the invertor using 230volt parameters, this allows the motor to deliver the original torque curve upto 230 Vac at 50 Hz but will continue to deliver 1.74 times more power at 400 Vac at 87Hz and from a smaller motor frame size. In this configuration the invertor must be double the size.

 

[Ttrees]

I'm taking that is the case for a real industrial machine...
I've seen some identical saws which have different options for motors,
so in that case (from a layman's perspective)
It "seems" like one could de-rate the motor power to the lesser spec motor
option on certain machines, and get away with it that way?
(provided this was an available parameter on a particular VFD)

Thanks
Tom

 

[Spectric]

Most machinery upto about 4Hp will have a single phase option as well as possibly a three phase version. They will both look and work the same, as a user you would not notice the difference without looking at the power connector. If you purchased a three phase machine with say a 10Kw motor you could not run that from an invertor and if you fitted a 3Kw motor you would find it not performing as designed, it would struggle. A good option then is the digital phase convertor which could power the 10Kw motor at 400 volts but without variable speed providing your power supply can take it.

 

[Sideways]

Download the manual for whichever Danfoss you're interested in and read it thoroughly first.
Danfoss' background is in HVAC and use of VFDs for energy saving control of pump and fan motors is one of the biggest applications of these devices. So far so good.
BUT
The safe overload profile for fans is typically different to pumps and both are different to the profile that you want for general industrial motors.
Once you've read up on this and understand what you are looking for and why, you can check the manual to ensure that the Danfoss unit can be configured to do what you need and can supply the short duration but higher peak overload currents that machinery motors can draw.
VFDs are NOT "plug and play".

 

[Spectric]

VFDs are NOT "plug and play".

It is a shame more people do not realise this, they are very sophisticated devices these days and the parameters that can be set are not getting any shorter. This is a good reason amongst others to just buy a decent VSD from a reputable OEM and not some bargain basement device fro an auction site.

 

[LJM]

Thanks for the comments so far. I realised from post I’d read here that VFDs are not plug and play, that they need to be set up (programmed) for the application in hand.

I’d erred toward the Danfoss because it’s a European brand that I recognise and they come up on eBay regularly.

However, I’m finding that they all require a 3 phase input, making this entire thread pointless, but for the very well informed comments from which I’ve learned a lot which applies generally and not just to the units I originally enquired about.

so thank you all.

 

[Spectric]

You will find the brands I mentioned all produce VSD's for either three phase use or running three phase from a single phase supply, but look at spending a few hundred quid.

 

[deema]

It might be helpful to know what your trying to power up? Sometimes there are more than one motor?
You have three options for the electrics I believe, which you might not have considered?
1. change the motor and switch gear. This generally adds value to the machine, people like single phase motors, no complexity.
2. if the motor is dual voltage (it will say 220 / 415) on the plate you can add a VFD. However, you will be removing any electrical brake as you can’t have both. The VFD can provide the breaking function depending on which you buy.
3. buy a digital phase converter. This creates genuine 415v 3 phase from a single phase supply. If you plan on getting other machines this is a good option as you can simply plug other 3 phase machines into it and use them without worrying about wiring etc. depending on how big unit you buy (power) you can run multiple machines off the one unit at the same time. It’s a cost effective solution IF you looking to buy other machines that could be 3 phase.
I generally recommend option 1, unless the person is buying other machines that are 3 phase. You need to know what your doing with electrics, a mistake and it bites often fately!
Brakes on machines are to avoid accidents by people getting impatient with the machine stopping before sticking fleshy bits into the moving parts. It’s not to reduce accidents whilst in use, which is what most people think. It will cut something off before you’ve even thought about hitting the stop button. There are machine regulations around use in commercial applications where you employ people which require machines to stop in a given time.

 

[LJM]

It’s a table saw. One motor, dual voltage, in fact designed for use with a VFD (according to manufacturer specs).

Options:
1. Value doesn’t matter; I’ve got very about £70 in this machine to date, and I’m happy with the 3kw power
2. The motor is intended for use with a VFD, so that’s what I’ll do; the ability to soft start it etc, I like.
3. I do have a big bandsaw, but I‘ll be sticking a VFD in that too, because I want to add a few more speeds

My uncle was an industrial electrician, so I have that aspect covered. This isn’t a commercial application, so whilst I Appreciate the function and value of a break, it’s not vital. I’ve come across a Seimens unit to which I can add a breaking module, if I wish.