How to figure out if a 3-phase motor has a brake without turning it on?

[mreza Salav]

I've got a bandsaw (documented here http://www.sawmillcreek.org/showthread.php?188600-Got-a-bigger-bandsaw-%28finally%29&highlight=)
with a 3-phase 3HP motor and I have ordered a VFD to run it using single-phase source of power.
The manual the manufacturer has e-mailed me indicates that the motor has a brake built in. Based on what I have read this makes using a VFD
to run this not feasible. I am somewhat doubtful about the manual as it's for all SNA/SNAC models, lacks a lot of details and says nothing about a foot brake, which
my saw has (BTW, I couldn't find a micro-switch, also the manual says the saw won't run with the doors open but there are no micro-switches for that either).

How can I tell whether the motor has a brake or not without turning it on (as I can't)? Should I open it up and look for the specific mechanism?
Or will a VFD work with it?

Here is a picture of the name plate on the motor:

236091

[Erik Loza]

Mreza, I would be surprised if that motor has an electronic brake. Motor braking is typically accomplished by a separate module that feeds DC current into the motor, in order to slow it down. If you just have the motor and nothing else, then it seems unlikely there is a motor brake. Also, I have never seen a vertical bandsaw which uses an electronic motor brake. At least not OEM. My suspicion is that they thought you were referring to the foot brake pedal or something like that.

Hope this helps,

Erik Loza
Minimax USA

[David Kumm]

Mreza, I know very little here but I assume you are talking about a mechanical brake right on the motor rather than a DC injection brake module. If you see a picture of the motor you can likely see if it has a brake in that the shaft is longer and the brake unit is attached so the motor looks much longer than normal. European machines are often required to have a brake of some sort so a manual might incorporate it even though most machines sent to the US don't have the brake. Either type should be able to be disabled although an injection brake might be wired into the vfd by someone brighter than me. Dave

[Rick Fisher]

Motoroti Bonora .. I love Italian names ..

My Jointer is a 12" Griggio .. it has an Electromagnetic brake.. The motor is made by CEG ..

Check the Motoroti Bonora website..

http://www.motoribonora.it/prodottie.htm


It appears Motoroti Bonora .. love saying that .. makes regular 3 phase motors, 3 phase motors with DC braking and 3 phase motors with AC braking .. I cant read the label on your pic but the motors on the website are identified by series .. probably one series matches the tag on your motor ..


.................... Took a good stare at your tag .. if the first letter is an H .. then it would indicate its just a normal 3 Phase motor .. No braking .. compare to the website link..

[mreza Salav]

Here is the print of the page in the manual which talks about the motor brake:

236105
I think it's a mechanism inside the motor (DC injected?) and the manual (sent to me by Griggio) says it will stop the motor within 6-10 seconds and can be adjusted on the motor.
My search online for the brand of the motor (Bonora) shows that indeed they have several ones that are 3-phase with brake, for example AR, ARR, K, series in the link below:

http://www.motoribonora.it/prodottie.htm

But the type of the motor on my saw (as shown in the picture in the first post) starts with H (something like H90U3k/2) which I am guessing it's an H series, which according to
the link above doesn't have a brake.

There are other things in the manual that are slightly different than on the saw and I'm guessing this is not the exact manual for my saw (eventhough I had given the model as
well as serial number and date of manufacturing of the saw to Griggio).

[mreza Salav]

Thanks Rick. I was typing my post as you posted your message and we have come to the same conclusion that this is a series H without motor brake (I hope!).

[David Kumm]

That is a compact version of the mechanical brake I was talking about. They refer to pads that activate when the power is cut and should be able to be disconnected but as Erik said, I'd be surprised if the motor actually had that. It is not an injection brake. Dave

[mreza Salav]

That is a compact version of the mechanical brake I was talking about. They refer to pads that activate when the power is cut and should be able to be disconnected but as Erik said, I'd be surprised if the motor actually had that. It is not an injection brake. Dave

Thanks Dave. I'm completely new to these animals (motors) so don't know what they are called. The manual called it "electro-magnetic brake".

The manual is pretty bad (to say the least), even worse than my Minimax J/P manual (that is bad too).
They have packed too many machines with different spec's into one manual and things aren't consistent. As I said, there is a foot brake on the saw with no mention of it in the manual, and the manual says that the saw won't run with door open (but there is absolutely no micro switch to detect this).

[Van Huskey]

Is the foot brake attached to a mechanical braking system at the lower wheel? If so I seriously doubt there is any form of motor braking.

If you are interested in a micro-switch for the mechanical brake it should be any issue to souce one (say from Grizzly) and attach it and run it through the low voltage loop of the VFD.

[Rick Fisher]

My manual for my Griggio Jointer was a manual for all their Jointer offerings as well.. It was not really specific to any particular model.. I would tend to go with the H and the foot brake ..

[mreza Salav]

Is the foot brake attached to a mechanical braking system at the lower wheel? If so I seriously doubt there is any form of motor braking.

If you are interested in a micro-switch for the mechanical brake it should be any issue to souce one (say from Grizzly) and attach it and run it through the low voltage loop of the VFD.

The foot brake is only mechanical I think: it's like a drum brake (on cars) that goes behind the lower fly wheel and there is no micro switch as far as I looked.
Adding one (to work with the VFD) sounds appealing. Which model of Grizzly are you referring to?

[Mike Delyster]

Hello Mreza

I don't remember seeing any wires running down to the lower wheel, but I could be wrong. If there isn't any that you can find, I would think it is only a mechanical brake.

[Rick Fisher]

The brake on my Jointer engages when there is no power to the motor. Sitting turned off, you cannot move the cutter-head with your hands.. There is a secondary switch, you turn the knob, then hit the power button.. The Contactor makes the clunk sound, but the cutter-head doesn't spin.. At that point, you can turn the cutter freely..

I believe there is a large electromagnet that when off, the disc brake stops the motor, probably by a big spring or something.. When you put power to the motor, the electromagnet goes hot and pulls the disc off the motor, allowing it to spin freely..

When the jointer is turned off, even with a really thick (around) 12" cutterhead, it comes to a stop really fast. Its impressive but I often wonder what the point is .. lol

I have a European Edge sander with the same set-up.. Same size motor 3kw.. when you turn it off, it stops now ! .. Like a second..

I suppose its safer but whatever.. One more thing that can pack it in 10 years from now ..

[Erik Loza]

Rick, that does sound like a magnetic lock. We use those on the stand-alone shapers. Ours is not a two-step process like yours apparently is, but when once the motor stops, you cannot rotate the spindle at all, by hand. More of a passive brake than an active one.

Erik Loza
Minimax USA

[David Kumm]

Rick, that does sound like a magnetic lock. We use those on the stand-alone shapers. Ours is not a two-step process like yours apparently is, but when once the motor stops, you cannot rotate the spindle at all, by hand. More of a passive brake than an active one.

Erik Loza
Minimax USA

Erik, any idea why SCMI uses that type of brake rather than an injection? Dave

[Erik Loza]

Well that is actually more of a "lock" for changing the spindle than a brake. Electronic motor braking is available, as well.

Thanks,

Erik Loza
Minimax USA

[Alan Schaffter]

Electro-mechanical braking is easier and cheaper to implement. The HF hoist motor on my I-beam hoist uses it. When the motor is energized to raise or lower, a solenoid at the back of the motor is also energized. It removes the pre-load spring tension on the disk brake. As soon as you stop, the solenoid is depowered causing the brake to re-engage. Works pretty well, unless you are trying to lift a 1300+ lb. planer! :eek:

http://www.ncwoodworker.net/pp/data/500/medium/PC140053.JPG

[mreza Salav]

Mike, I think you are right. There is no switch for the foot brake.


The brake on my Jointer engages when there is no power to the motor. Sitting turned off, you cannot move the cutter-head with your hands.. There is a secondary switch, you turn the knob, then hit the power button.. The Contactor makes the clunk sound, but the cutter-head doesn't spin.. At that point, you can turn the cutter freely..

I believe there is a large electromagnet that when off, the disc brake stops the motor, probably by a big spring or something.. When you put power to the motor, the electromagnet goes hot and pulls the disc off the motor, allowing it to spin freely..

When the jointer is turned off, even with a really thick (around) 12" cutterhead, it comes to a stop really fast. Its impressive but I often wonder what the point is .. lol

I have a European Edge sander with the same set-up.. Same size motor 3kw.. when you turn it off, it stops now ! .. Like a second..

I suppose its safer but whatever.. One more thing that can pack it in 10 years from now ..

The lower fly wheel rotates freely when the saw is off (haven't turned it on ever myself). So there is no brake (at least of the type you have on your Griggio machines).

Thinking of adding the micro-switch for foot brake of the following Grizzly bandsaw (that is also 3-phase) if it is something I can do with a VFD (item 113 in the diagram):

http://www.grizzly.com/products/G0514X3/parts/MAIN

I might add it if it is an easy modification.

[Mike Delyster]

I thought some more about when I seen that saw running and I'm 100% positive that when Randy shut the power off to the saw the bottom wheel coasted for a long time, it had no band on it as you seen from the pictures. It should be easy to wire in a micro switch for braking with the VFD, mounting the switch will probably be the hardest part.

I think it has a magnetic starter on it now, which probably won't work with the VFD, but with the VFD the on/off switch is low voltage so you will be able to use just about any type of switch.

What type of VFD did you end up ordering?

I've found when hooking a three phase machine up to a VFD, it is easier to take all the original wiring off first and start over. Their not that bad to wire though, when you figure out what switch's and micro switch you want to use send me a pm and I will make you a drawing of how it needs to be hooked up.

[Alan Schaffter]

There is no reason to have a separate braking circuit if you have a VFD. VFD's can be programmed to inject braking, however for serious braking you also need to add a braking resistor which is typically an option not normally supplied with the basic VFD. You only need a start/stop circuit. If you want the saw to stop if the blade breaks you will need a micro-switch mechanically set up to open or close when the blade brakes. That switch can be wired in series with the VFD's remote run/stop switch so that anytime the saw stops, whether initiated by the user or because the blade has broken, VFD braking will be initiated.

[Van Huskey]

There is no reason to have a separate braking circuit if you have a VFD. VFD's can be programmed to inject braking, however for serious braking you also need to add a braking resistor which is typically an option not normally supplied with the basic VFD. You only need a start/stop circuit. If you want the saw to stop if the blade breaks you will need a micro-switch mechanically set up to open or close when the blade brakes. That switch can be wired in series with the VFD's remote run/stop switch so that anytime the saw stops, whether initiated by the user or because the blade has broken, VFD braking will be initiated.

I think he wants to wire the foot brake, don't think he mentioned the blade breaking. His foot brake doesn't have a micro-switch, most current models do, most foot brakes work faster than motor braking and you can activate them without moving your hands and from many more areas around the work table.

[Alan Schaffter]

I think he wants to wire the foot brake, don't think he mentioned the blade breaking. His foot brake doesn't have a micro-switch, most current models do, most foot brakes work faster than motor braking and you can activate them without moving your hands and from many more areas around the work table.

Put a second micro-switch in series on the brake pedal, then he has all bases covered!

[Van Huskey]

Put a second micro-switch in series on the brake pedal, then he has all bases covered!

Exactly, thats his plan.

[Rick Fisher]

Anyone tell me how to wire a micro switch like that to a Mag starter ? I have an old SCM Bandsaw and would love to have power cut off by the foot brake.

You can use a braking resistor on a VFD but the braking is not super fast.. Its limited I believe for the same reason VFD's don't like motor brakes.. I should make a little video of these machines brakes.. Its impressive to me, but still sort un-needed..

http://i335.photobucket.com/albums/m455/jokerbird_photo/th_00005.jpg (http://s335.photobucket.com/albums/m455/jokerbird_photo/?action=view&current=00005.mp4)


Click on the picture .. its very short ..

http://i335.photobucket.com/albums/m455/jokerbird_photo/th_00006.jpg (http://s335.photobucket.com/albums/m455/jokerbird_photo/?action=view&current=00006.mp4)

[Mike Delyster]

Run another stop button (micro switch) in series with the stop button on your Magnetic starter which will be NC (normally closed) the motor won't start again until the start button NO (normally open) is depressed. These switch's need to be momentary switches.

[Alan Schaffter]

A normally closed momentary micro-switch is wired in series with the "stop" button. The stop button is typically wire via a spare set of contactor contacts connected in a "latching circuit" to the contactors coil. You need to make sure the micro-switch is rated for the voltage used by your mag starter. If it is an old mag starter with a small transformer in it, it will likely have a 24VAC low voltage control circuit like my unisaw with the control box on the back and buttons up front and can be wired with 18 - 20 gauge bell or hook-up wiring. But if it is a newer style all-in-one full voltage mag starter, it could be 220V, so you better be careful wiring it and will need a special microswitch.

[Mike Delyster]

A normally closed momentary micro-switch is wired in series with the "stop" button. The stop button is typically wire via a spare set of contactor contacts connected in a "latching circuit" to the contactors coil. You need to make sure the micro-switch is rated for the voltage used by your mag starter. If it is an old mag starter with a small transformer in it, it will likely have a 24VAC low voltage control circuit like my unisaw with the control box on the back and buttons up front and can be wired with 18 - 20 gauge bell or hook-up wiring. But if it is a newer style all-in-one full voltage mag starter, it could be 220V, so you better be careful wiring it and will need a special microswitch.

Hello Alan

Looks like I was typing at the same time as you. Thanks for the heads up about some of the newer Mag starters, I haven't ran into one of those yet.

[Van Huskey]

Rick what sander is that?

[mreza Salav]

Mike, I got that FM50 series you suggested from Factorymation. It's on it's way with UPS (and I dread the brokerage fees they are going to collect :().
I will certainly benefit from your help in doing the wiring as I've never done this. Will send you an e-mail (or if you have a copy of that VFD and a wiring diagram you can e-mail me).
I'd like to get this running and then later on add a micro-switch (for the foot brake). Thanks again.

[Van Huskey]

When you have it all "open" and doing the switch wiring ext, I would place a piece of bell/thermostat wire from the switch down to the foot brake (leaving several extra inches for hookup later) and back to the VFD so when you do wire the micro-switch you can do it all in the lower area without having to run all the wires.

[Mike Delyster]

When you have it all "open" and doing the switch wiring ext, I would place a piece of bell/thermostat wire from the switch down to the foot brake (leaving several extra inches for hookup later) and back to the VFD so when you do wire the micro-switch you can do it all in the lower area without having to run all the wires.

Thats a good idea Van, it will make life simpler later.

Mreza I have instructions for that VFD, I will make up a drawing and make a list of where to set the parameters to get started, then you can always fine tune it from there.

[Van Huskey]

Just as an FYI the printed manual with the FM50 will probably cover everything you need BUT if not the CDROM manual is far more complete.

[Rick Fisher]

Van, its a Felder ..

[Van Huskey]

Very nice Rick!

[mreza Salav]

thanks folks. I'll wait for the unit to arrive to take a look at it and the manual. If I had more questions I'm sure I can use your help.

[Kirk Poore]

thanks folks. I'll wait for the unit to arrive to take a look at it and the manual. If I had more questions I'm sure I can use your help.

If this is the first time you've seen a VFD manual, and you're not an electrical engineer, you'll be back with questions. The FM50 manuals are allegedly better than most, but they are in no way easy to figure out. There are no examples or tutorials, and the various function settings are, at best, sparsely described.

Kirk
who hopes things have gotten better over the last two years, but seriously doubts it...

[Erik Loza]

Mreza, if you do this, please create a DIY thread. I have had several customers tell me over the years that they retrofitted VFD inverters to their saws and always asked them to email me some photos or whatever, but haven't seen any as of yet, and would really like to see how the end result looks/was wired/user feedback/etc. The process seems pretty straightforward but I have never personally done it, so it would be awesome if there was a thread I could point guys to and say, "Look, this is how you do it".

Thanks,

Erik Loza
Minimax USA

[mreza Salav]

Erik, I'll try to post a step by step thread here.
I don't have a degree in electrical eng. but I'm not totally illiterate either ;)

[mreza Salav]

Just a quick update: the VFD arrived late last week (and had to pay $41 to the ~@#!@ UPS for brokerage so they pay $9 tax to government :mad:)
Over the weekend I spent some time to remove all the wiring of the motor and use the VFD to run the bandsaw.
It worked pretty well (in the test case setting). First time I ran a 3phase motor :)
Now I have to put things back in place and find a location to mount/secure the VFD and find a switch to use to turn on/off the saw.
Since it will be a low voltage (12V) circuit I can use even a small toggle switch.
I have taken some photos and will take many more along the way and post in a separate thread but these have to wait a little longer as I'm super busy these days.

[Rod Sheridan]

Good news, just remember to program it so it doesn't auto-restart after a power failure (if it's an option on that drive).................Regards, Rod.