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RB211
02-17-2019, 11:23 AM
I never gave it much thought with my mill, but on the lathe I've been looking at it more in depth. Thought about getting a DIN mount circuit breaker to put inside the box as recommended, but the line it will be plugged into is already protected by a 30 amp circuit breaker at the box. Fast acting fuses? Only ones I can find are from China with the nice DIN mount holders, but I don't trust what could be fakes.
Magnetic relay? In case of a power reset or the lathe is plugged in with the run switch on? Why? The VFD can be programmed to NOT run when first powered on if the external run command is selected on. As for turning the VFD on and off, I think a DPST switch may be adequate, one that can handle 220 30amps, or probably I should just repurpose one of the 24v relays in the lathe to serve that function, triggered by a SPST toggle switch, or maybe a key lockout.
As for the E-Stop, I am hoping on the lathe, I can select between NO and NC on the switch, and wire it to the VFD. I do not want the power to be cut off to the VFD in case of the E-switch use, because I still want that braking resistor to do its job to stop the spindle. Maybe do away with the safety switch for the gear cover or use it along with the Estop. I wish the VFD could be set to use normally closed inputs for that function.
The power light on the front of the lathe will be also energized by the VFD with one of its built in relays, assigned the function of "power on". The second built in relay will be assigned the function "fault", and think I will have it switch on a red light.

Noise filters... Never used them, don't think I will need them, thoughts? A/C reactors, don't think I need one for this low voltage application.

The Hammond 16x12x6 box will have a 120mm computer cooling fan with a screen and filter at the bottom. I will make a steel heat shield between the resistor and VFD, and will cut out an opening at the top that will have a screen on it for the hot air to expel out of.https://uploads.tapatalk-cdn.com/20190217/cc129fe2be0aa33a3439d290169e8b7e.jpg

MTNGUN
02-17-2019, 11:33 AM
Looks good. My VFD's are mostly exposed (not strictly up to code) but I learned the hard way that it's a good idea to at a minimum make some sort of shield over the top to keep water out. Had a plumbing leak on the 2nd floor, dripped into a VFD downstairs and let the smoke out.

lakeside53
02-17-2019, 11:34 AM
Put a small thermostat in the box at the top, have an exit grill/louver on the top right, make the the fan blow IN, larger filter above the fan, NOT out

Why? fan blowing out makes the box into a vacuum cleaner... lower pressure on the box just acts a dirt collector. Done right you'd be surprised how little the fan will kick in.

Use a nema "r" rated box for Drip proof

Here's my 3hp 2x72 belt grinder - box mounted lower left in a filthy environment, years of use with no issues. Old 24v laptop power supply, 24 volt contactor, Thermostat etc, (set to a few degrees higher than when the VFD fan kicks in), cut down furnace filter. 3 inch fans are 24v and fit into the box knock outs. No need for separate fuses or breaker of your supply is
protected accordingly. Braking resistor at top is a 120v 300 watt engine pan heater.

https://i238.photobucket.com/albums/ff150/lakeside53/x72%20Belt%20grinder/DSCN2351Medium-1.jpg


http://i238.photobucket.com/albums/ff150/lakeside53/x72%20Belt%20grinder/DSCN2362Medium.jpg

My CNC mill vfd box. Mounted in relatively clean environment so no "filter" other than a chip screen. Fan is programmed to come on only during spindle-on and 30 seconds after, and again blows in. Reused an old transfer switch box.

http://i238.photobucket.com/albums/ff150/lakeside53/misc%20linked%20uploads/DSC_8960Medium.jpg

Just above the lower right are din rail connection blocks (insulated) and a "finger safe" fuse holder (for external 120v plugged in devices). These are great and you can get them on ebay used cheap. There are two sizes of the fuse holders so take care.. the 300v CC are smaller... I think; the 600v huge. Single, dual and 3 pole available (if you care, if used as a means of disconnection, code requires all poles disconnected on opening the holder). I like those with an indicator - glows when the fuse is blown.

Search for "ferraz shawmut fuse safe".. many other but this will get you started.

chipmaker4130
02-17-2019, 12:17 PM
You can get DIN rail mounted fuse holders into which you can put ordinary glass fuses of your choice. The holders can be fully enclosed with a hinged, snap-out section for easy fuse change. Maybe that's what Lakeside is talking about, I can't really see his.

edit: I personally like Omron stuff. Seems to be very good quality.

wierdscience
02-17-2019, 12:33 PM
My CNC mill vfd box. Mounted in relatively clean environment so no "filter" other than a chip screen. Fan is programmed to come on only during spindle-on and 30 seconds after, and again blows in. Reused an old transfer switch box.



So the fan is powered directly off the aux.contacts on the VFD,or off a spearate relay?

What are your thoughts on adding a line reactor on the output side of the VFD?I've done that on a couple of applications that see long runtimes and noticed the motors run noticeably cooler.Might be a good idea on a lathe or a mill?

lakeside53
02-17-2019, 12:48 PM
The fan is switched from the VFD aux relay contacts in one case (cnc mill box) , separate in the other (grinder). Output reactors are great if sized correctly. They certainly protect the motor insulation, maybe the bearings (Jerry will probably tell me I'm wrong, but.. ;)) and a LOT less audible carrier noise at lower rpm. I have one for my mill... one day I'll fit it permanently...

back later... need to go shovel some snow.

MaxHeadRoom
02-17-2019, 01:00 PM
S
What are your thoughts on adding a line reactor on the output side of the VFD?I've done that on a couple of applications that see long runtimes and noticed the motors run noticeably cooler.Might be a good idea on a lathe or a mill?

I have installed VFD's since the 80's and have used a reactor between VFD and motor, this is on the recommendation of a few suppliers, makes it easier on the VFD as well as the motor, particularly if it is non-vector rated/normal 3ph motor etc.
Max.

J Tiers
02-17-2019, 02:51 PM
I never gave it much thought with my mill, but on the lathe I've been looking at it more in depth. Thought about getting a DIN mount circuit breaker to put inside the box as recommended, but the line it will be plugged into is already protected by a 30 amp circuit breaker at the box. Fast acting fuses? Only ones I can find are from China with the nice DIN mount holders, but I don't trust what could be fakes.

If you satisfy the requirements of the VFD, per the manual, then it does not matter much where the circuit protection is. Some ask for a CB, some for fuses. It just depends on what is needed to satisfy UL508.


Magnetic relay? In case of a power reset or the lathe is plugged in with the run switch on? Why? The VFD can be programmed to NOT run when first powered on if the external run command is selected on. As for turning the VFD on and off, I think a DPST switch may be adequate, one that can handle 220 30amps, or probably I should just repurpose one of the 24v relays in the lathe to serve that function, triggered by a SPST toggle switch, or maybe a key lockout.

The VFD may be rated to function as a motor controller, and if so you won't need other stuff.


As for the E-Stop, I am hoping on the lathe, I can select between NO and NC on the switch, and wire it to the VFD. I do not want the power to be cut off to the VFD in case of the E-switch use, because I still want that braking resistor to do its job to stop the spindle. Maybe do away with the safety switch for the gear cover or use it along with the Estop. I wish the VFD could be set to use normally closed inputs for that function.
The power light on the front of the lathe will be also energized by the VFD with one of its built in relays, assigned the function of "power on". The second built in relay will be assigned the function "fault", and think I will have it switch on a red light.

Another place where if the VFD is rated as a motor controller, you may only need the e-stop switch and suitable programming. At least unless you need a "higher level" type of e-stop. Some have to physically remove power, but you likely do not.

Make sure the relay in the VFD is rated for what you want to use it for. Some are only good for small loads.



Noise filters... Never used them, don't think I will need them, thoughts? A/C reactors, don't think I need one for this low voltage application. Reactors lower the stress on the motor on the one hand, and they help limit fault current in case of shorts on the output. But they are not mandatory in most cases


The Hammond 16x12x6 box will have a 120mm computer cooling fan with a screen and filter at the bottom. I will make a steel heat shield between the resistor and VFD, and will cut out an opening at the top that will have a screen on it for the hot air to expel out of....

Blowing air in is good, with a decent intake filter it does not draw in dust as mentioned above.

With a suitable sized box, no fan is even needed, the box will transfer enough heat. Minimum size boxes may require fans. The resistor will not get that hot in all likelihood, but with a lot of starting and stopping, it may be a decent reason for a fan.

Paul Alciatore
02-17-2019, 08:32 PM
I am not sure I fully understand all of your concerns. But two things jump out at me.

First, a fuse. I assume you want a fuse on the line power going to the VFD. Fuse holders are basically inexpensive, generic components. For 220 Volts you would need two of them. While you can mount them on a DIN rail inside the box, I would use a style that mounts in a circular hole in the box. They can be purchased from many sources, including any electronic supplier, McMaster, and all over the internet. You only mentioned 30 Amps/220V so I am going with that. Here's just one:

https://www.mouser.com/ProductDetail/Bussmann-Eaton/BK-HKP-W-R?qs=jGANiKWBgcii7EY5IKdVrg%3d%3d

That way, if the fuse blows, you can change it from the outside and you don't have to open the box. You can select from a wide variety of standard, 30 Amp fuses that will fit in it, including fast and slow blow types.

The second thing is putting the VFD inside a metal box. You should carefully read the installation instructions and heed every word that they say about ventilation. You seem to also have a power resistor mounted inside that box, I assume for breaking. But every time you stop, it will put ALL of the mechanical energy that is being removed into HEAT in that resistor. So the inside of the box is going to get hot. I think you will need a very good ventilation system for that box if you do this. Or you will blow up your nice, new VFD.

OK, a third thing. I know that many controls that are labeled "E-Stop" use the complicated electronics of a controller like your VFD to effect this function. In My Humble Opinion, that is not a proper E-Stop. E-Stop means EMERGENCY Stop as in, your life or limb is in danger and you want to stop it NOW. I have recently built a control box for my lathe. It does not incorporate a VFD, just a contactor for ON and OFF. But the Stop button, which is about as good of an E-Stop as you can get, is designed to actually interrupt the current that holds that contactor ON and it will not re-start until the Start button is pressed again. This will also happen in a power outage, even a brief one. Absolutely NO electronics are involved and if there is a wiring fault, that would most likely be an open circuit which would also stop the machine. This does not activate any dynamic breaking, but it does positively remove all power from the machine. With the proper contactor a current dampening resistor could have been incorporated for breaking. I did not think that was really necessary with the fractional HP motor on my lathe.

lakeside53
02-17-2019, 08:57 PM
Fuses... check the VFD manf recommended fuse TYPE as well as it's voltage/current. I rarely use the glass type fuses for industrial controls as fuse type selection is limited.

Also, not to be picky, but if a fuse blew I like to look inside to see what's up. A vfd should not be able to blow the correct fuse unless there is an internal fault. Fuses/breakers are there to stop fires, not protect the motor or device.

J Tiers
02-17-2019, 11:33 PM
The fuses are typically a fast blow fuse, intended to pass the "ball of fire" test in UL 508 that checks the currents to ground in fault conditions. The UL test puts a fuse of a certain type in series with the ground lead, and then faults are induced. The fault and arcing cannot blow the ground fuse.

So the series fuse is intended to open before the ground fuse does in the test. That's pretty much the reason for the exotic fuses in certain cases. There are other reasons as well, but that one is a "must".

gellfex
02-17-2019, 11:41 PM
I'm confused as to why all this is necessary. I've had 3 VFDs for many years, didn't do anything but external controls on one. Never a problem. Bought braking resistors for the mill, but adjusted settings and never installed them.

J Tiers
02-17-2019, 11:56 PM
The fancy fuses likely are not. breakers will open faster than you can think if there is a short. It's a question of what happens with the VFD.... Does it burn, or just pop the breaker? That's what UL is concerned with. Technically, it is not UL recognized if the conditions of use ae not followed, which includes the circuit protection the manufacturer specifies. You can tell how hard it was for the unit to pass UL, depending on if a breaker is OK, and if not, how expensive the specified fuse is. ;)

Braking resistor "might be". depends on how fast a stop is necessary, or, I suppose, how fast a stop is "wanted". If it trips out on overvoltage when a typical stop is done, then you probably need it. If you never see an O/V error when stopping it, then you don't.

Some folks like to have all the bases covered, some folks don't worry about it unless they have an issue.

lakeside53
02-18-2019, 12:27 AM
Braking resistor "need" also depends on your speed and mass. I spool my BP vari-speed up to 6000 often, and more... almost impossible to use without controlled braking via a braking resistor. Sure.. I could simply freewheel to a stop but life is too short for that. Also flipping from FWD to REV. I like a couple of seconds (doesn't happen from 6000!)... YMMV

RB211
02-18-2019, 05:32 AM
My Bridgeport could use a braking resistor as well, so I decided to go with one on a 12" lathe since there is much more rotating mass

wierdscience
02-18-2019, 08:59 AM
Braking resistor "need" also depends on your speed and mass. I spool my BP vari-speed up to 6000 often, and more... almost impossible to use without controlled braking via a braking resistor. Sure.. I could simply freewheel to a stop but life is too short for that. Also flipping from FWD to REV. I like a couple of seconds (doesn't happen from 6000!)... YMMV

I was told by an AB controls tech that if the expected braking load was over 50% of the internal braking capacity or the frequency of stop/starts was greater than 10 per hour an external resistor was needed.As he put it "loosing the internal resistor means loosing the drive" so buying the external resistor was cheap insurance.This was awhile ago,but it sounded like sage advice so I typicaly follow it.

lakeside53
02-18-2019, 10:44 AM
Lathes are an interesting problem with the possibility of large variances in inertial mass. In this case a combination of DC injection (tricky to get right) and dynamic braking can help. An external dynamic braking unit (or over-sized vfd for better breaking unit) is another option to avoid duty cycle issues.

I have a problem currently... a 1hp motor that can be required to start/stop 20 times a MINUTE.. stupid design... it's on a conveyor belt and if packages get too close it has to start stop breifly to space them out. URGH... only happens every now and then (when we really need the volume) and invariably blows the motor overload stopping everything. Maybe 30 times an hour is ok intermittently, but that still shortens the rotor life unless I use vfd style soft start and quick stop.

RichR
02-18-2019, 11:12 AM
... I have a problem currently... a 1hp motor that can be required to start/stop 20 times a MINUTE.. stupid design... it's on a conveyor belt and if packages get too close it has to start stop breifly to space them out. URGH... only happens every now and then (when we really need the volume) and invariably blows the motor overload stopping everything. Maybe 30 times an hour is ok intermittently, but that still shortens the rotor life unless I use vfd style soft start and quick stop.

Sounds like a task possibly better suited to some kind of clutch mechanism.

QSIMDO
02-18-2019, 11:18 AM
This guy did a series of videos on a lathe VFD https://www.youtube.com/channel/UCeKpbMimEGgLM_0tnghfoVw/videos
It was far more technical than the 2 mills I've done but should be helpful when I do my lathe and try to keep some of
the stock control positions.

J Tiers
02-18-2019, 11:38 AM
I was told by an AB controls tech that if the expected braking load was over 50% of the internal braking capacity or the frequency of stop/starts was greater than 10 per hour an external resistor was needed.As he put it "loosing the internal resistor means loosing the drive" so buying the external resistor was cheap insurance.This was awhile ago,but it sounded like sage advice so I typicaly follow it.

Must have been a while ago, because it does not make a lot of sense. Most drives have no internal resistor of that sort, and they shut down on overvoltage before they are damaged. "Losing the drive" is just not expected, and has not been for a decade or two. Many low cost drives do not even have connections for a resistor.

wierdscience
02-18-2019, 03:28 PM
Must have been a while ago, because it does not make a lot of sense. Most drives have no internal resistor of that sort, and they shut down on overvoltage before they are damaged. "Losing the drive" is just not expected, and has not been for a decade or two. Many low cost drives do not even have connections for a resistor.

Ya,this was late 90's early 2000's.Most of the smaller drives don't require an output reactor either until you get above 2hp.I giess they figure what's a couple hundred bucks if we let the smoke out.

wierdscience
02-18-2019, 03:30 PM
Sounds like a task possibly better suited to some kind of clutch mechanism.

Yes agreed,a clutch is in order,air clutch preferably.

RB211
02-19-2019, 01:54 AM
My Teco 7300 is kind of fancy, has built in PLC functions. The DC injection braking however is only rated to 20% of the torque as they list it. The VFD on the mill definitely needs an external resistor as it hardly does anything. Probably OV immediately, something I need to explore when I get back home. That guy on YouTube is the one I watched and triggered the reason for this threads existence.