Thread: VFD switching on a Hercus 260

Originally Posted by jack620

Just out of interest, I found the squeal at 4kHz quite annoying, but at 5kHz quite acceptable. After my next hearing test I'll work out which frequency my hearing is most degraded at and set that on my VFD!

Try and set the nrd parameter to "yes". NRD is "Motor Noise Reduction" by using a random frequency modulation (see page 57 of your manual).
In some drives, I recall that selecting odd chopper frequencies automatically enables the "random frequency modulation", whilst selecting even chopper frequencies turns it off. That way a lower chopper frequency may sometimes appear to make less audible noise.

I'd echo Ray's comments. I don't have anything like his experience with this type of thing. While I used precision 3 phase motor drives, they were an integral part of the equipment that I was working on, and not stand-alone independent devices. The theory was the same, but the application nothing like the same.

Having said that, I can honestly say this is the only forum on which I've seen people encouraging others to "upsize" their motor controllers. Chris I'd draw your attention to the Caution on page 9 of the link you kindly provided. One of the reasons I wanted to emphasise these as motor controller instead of single to 3 phase converters, is that they do SO much more than just converting single to 3 phase. One of their primary functions, at least in industry, is to help protect the motors. As can be seen, if you're operating it vastly different to the designed application, they won't operate to their full potential.

Thanks again for the link and information.

Pete

Originally Posted by RayG

Hi Chris,

Set it to 16Khz and that will keep teenagers out of the workshop....

No problem keeping my teenagers out of the workshop Ray. I don't think they even know where it is.

Originally Posted by cba_melbourne

Try and set the nrd parameter to "yes". NRD is "Motor Noise Reduction" by using a random frequency modulation (see page 57 of your manual).

I saw that setting while I was ploughing thru the manual. I'll give it a go.

Originally Posted by jack620

Josh,
Here's my wiring diagram. For this to work I needed to enable 3-wire control and select LI3 as the reverse command input. I haven't shown the speed control pot as that's dead easy to wire up.
Chris

Thanks Chris, I was just interested to see which way you ended up going about it, plus I'm sure other people will like having a reference.

Any plans on using the stop position on the switch? From the photo it looked as if there might be a contact in the off position? If so you could potentially run your stop signal through the switch directly if is a normally closed contact or put a slave relay in if it is a normally open(some switches you can open up and rotate the cam for each position to change the contact). Not sure if it would be worth the bother, owners choice .


So on the subject of VFD sizes, to be honest it really does not matter all that much if it is oversized other than cost, most requirements for the machines we are talking are simplest form motor control.

At the moment I can think of only three real situation where I would put in a larger drive and they are:
1. The VFD needs to be derated because the maximum ambient temperature is too high. (pretty common on AU mines)
2. The mains supply is 480V SWR and running 415V load. Needed to compensate for the extra ripple on the DC bus. (or flaky supply ie genset)
3. The installation is in a public space where "VFD noise" is an issue, ie higher switching frequency required, generally around 16KHz.

One thing to note on VFD sizing is heat, a lot of the time they get shoved into an enclosure with insufficient cooling for the required duty. A typical VFD will generate 3-5% of its loading as heat. So in that sense it is beneficial to have a larger drive.

-Josh

Originally Posted by Pete F

Having said that, I can honestly say this is the only forum on which I've seen people encouraging others to "upsize" their motor controllers. Chris I'd draw your attention to the Caution on page 9 of the link you kindly provided. One of the reasons I wanted to emphasise these as motor controller instead of single to 3 phase converters, is that they do SO much more than just converting single to 3 phase. One of their primary functions, at least in industry, is to help protect the motors. As can be seen, if you're operating it vastly different to the designed application, they won't operate to their full potential. Pete

Pete, is this is the caution on page 9 of the manual?

"CAUTION
RISK OF DAMAGE TO THE MOTOR
Motor thermal protection will not be provided by the drive if the motor rating current is less than 20% of the rated drive current. Provide
an alternative means of thermal protection.
Failure to follow these instructions can result in equipment damage"

The way that I read that, it says that you can safely use a motor as small as 20% of the drive rating. That is a 5 times smaller motor. If it was a 1HP VFD, you could safely use it with a motor as small as 0.2HP, with all protections perfectly working. You just need to tell the VFD the nominal motor current. And do a self tuning if you want to use sensorless vector control. I did only recommend upsizing the VFD one or two sizes above the motor rating, not 5 times larger. If you have a 0.5HP motor, I do recommend a VFD of at least 3/4HP or better 1HP. I think this is good advise. Chris

Originally Posted by Brobdingnagian

..............
At the moment I can think of only three real situation where I would put in a larger drive and they are:
1. The VFD needs to be derated because the maximum ambient temperature is too high. (pretty common on AU mines)
2. The mains supply is 480V SWR and running 415V load. Needed to compensate for the extra ripple on the DC bus. (or flaky supply ie genset)
3. The installation is in a public space where "VFD noise" is an issue, ie higher switching frequency required, generally around 16KHz.
..........
-Josh

Josh, I have one more to add:

4. The VFD is intended for a lathe. A larger VFD will prvide better braking, without going to the expense of an external braking resistor. There is very little price difference in upsizing a small HP VFD, but a brake resistor can cost more than 50% of the new VFD.

Chris

Pete,
I put the "350 chev in the mini moke" for the reason that Chris (CBA) gave, so that i didn't have to use as many belt changes. I have found though that the lathe is rigid enough to use a lot of the motors power, well as much as the belts can transfer. I will say though that there is HP and there is HP. The 1/2hp GE motor that came of the machine is the same frame size as the 2hp one on there now. It had more go than the 1hp DC motor i tried, and the 2hp motor now does not have 4 times the grunt, probably not even twice.
The reason for the larger drive, believe it or not, was price. The cheapest Huanyang i could buy at the time was a 3hp.

Cheers,
Ew

PS, my yr1 teacher drove a Californian, isn't it funny the things you remember....

My prep teacher wore a mini skirt. Pity I was too young to appreciate it.

Originally Posted by Brobdingnagian

Any plans on using the stop position on the switch? From the photo it looked as if there might be a contact in the off position?

Not at this stage Josh. The rotary switch has a spare set of poles which could probably be incorporated into the Stop circuit feeding LI1. I'll mull it over.


In all the excitement about VFD sizing you blokes obviously missed my question about the jog function. Anyone use it, and if so, what for?

Chris

Hi Chris,
Back on topic now.......yes I have jog buttons for fwd and rev, I use them often if using a tap or die, and to turn the spindle over to inspect etc when the lathe is in a low gear and its hard to turn by hand.

Cheers,
Ew

Thanks Ewan. I'm going out now to hook up a temporary switch and see how the jog works on this VFD. It's fixed at 5Hz with 0.1s ramp up/down times.

Originally Posted by Ueee

yes I have jog buttons for fwd and rev,

That doesn't seem to be an option on my VFD, so I've added a toggle switch for selecting either continuous running or jog. The green pushbutton is either start or jog depending on the position of the toggle switch. The FWD/REV switch selects FWD or REV jog.

Chris

Edit- revised wiring diagram added.