# Invertek VFDs



## Ceej0103 (Feb 25, 2022)

Hello,

I'm rebuilding a Jet 1340 lathe and wanted to replace the single phase 3hp motor with a three phase motor and VFD control.  Primarily because the circuitry in the lathe's cabinet was toast and I didn't know how to fix it.  At the time, contactors, overloads, relays, and all that jazz had me confused. I'm now more confident in that regard, but I still like the VFD and 3-phase over single phase/single speed. Probably a little overkill, but I purchased a 5 1/2 HP Marathon motor with a 112M frame (same frame as what came off my Taiwan-made JET 1340), inverter rated for continuous duty.  Since I invested in a nice motor, I decided to invest in a nice VFD as well.

I purchased the Invertek Optidrive E3.  I had very little experience with VFDs and no experience using low voltage control circuits.  Everything I had done was on the VFD's control panel.  The manual was still a little overwhelming, but I was able to get the motor up and running. From there, I was a little out of my league.

Here's the reason I'm writing this post.  888-862-5659. That's the technical support for Invertek. I have no way of expressing how F*#$ING amazing these guys are.  Specifically a guy named Matt. There was no ticking meter and the feeling of being rushed.  He wanted to know the intimate details of my application to make the drive work for me how I wanted it to work.  He was as much an educator as he was a technical resource.  Making sure I understood the concepts of advanced motor control using their VFD so I could apply those concepts to the information contained in the charts within their manual.  Basically he taught me to fish instead of giving me a fish. I went from knowing virtually nothing about the capability of a VFD (beyond changing single phase to 3 phase) to doing some rather advanced wiring on my lathe.  This includes:

Integrating all the existing safety limit switches and applying a fast-stop command if they're tripped during operation (opening panels that shouldn't be opened during operation). This includes lock-out until the condition is rectified (ie. cant start the lathe if I opened the change gear door until I close it). Chuck goes from 1800 RPM to 0 in less than a second.
Integrating limit switches for apron forward/reverse control, subject to lockouts. Won't work if any Normally Closed safety limit switch is opened. 
Integrating limit switch for brake control with DC Injection Braking.  No more brake pad running on a motor pulley journal.  I put a little pressure on the brake pedal, a lobe on the shaft closes a limit switch, and the chuck stops in about 3 seconds.  I put the pedal to the metal and the shaft's second cam engages a second limit switch and initiates a fast-stop, which brings the chuck to a dead stop in less than a second.  I haven't done enough research on the effects on the headstock gearing when I bring the lathe from full speed to dead stop that quickly.  Until I do my research on the wear/tear of that action, I'll only use fast-stop when it's necessary.  If I find that there's virtually no impact on the health of the gears using fast-stop, I'll probably just switch to always fast-stopping.
Low voltage switches have replaced the old high-voltage switches that were crusty and decaying.  
I have 2x 30mm illuminated push button latching switches that now control: flood coolant on/off, lathe lights (2 overhead, 1 snake light) on/off.
1x 22mm keyed switch.  This runs to a contactor that interrupts the 3 legs of power between the VFD and the motor.  When key is inserted and turned to on, contactor coil is engaged and power can pass from VFD to Motor.  When not in use, key is removed and tucked away where curious kids can't find it. 
1x 22mm 10k Potentiometer to control lathe speed.  I will be installing a tachometer soon. 
I have 1 original hole remaining with a 30mm illuminated latching push button....not sure what I'll use it for....maybe to turn on my TV?


So, this post has gotten really long, but I felt folks may have a greater appreciation for the support I received when going from VFD-dumb to where I am now using Invertek's free support.  The long and short of it is, if you're in the market for a drive and don't mind paying a little more than the generic Chinesium drives on Amazon, and this is your first rodeo, you might be wise to get an Invertek and call Matt for some help.


----------



## markba633csi (Feb 25, 2022)

Let's hope they keep him- good people tend to disappear, they get stolen by other companies or they start their own 
-M


----------



## BEI (Mar 18, 2022)

It’s interesting to me how impeccable the timing is of your post. I just bought a 3hp three phase lathe that I’m trying to figure out how to power up, VFD or rpc or motor swap. I suspect a VFD would be the cheapest way to go but I don’t know my way around those things. Your post about Invertek seems like a good possibility for me. Thank you.


----------



## Dabbler (Mar 18, 2022)

@Ceej0103 @BEI would be helped if you described your steps and how long it took to change over everything.


----------



## Ceej0103 (Mar 18, 2022)

BEI said:


> It’s interesting to me how impeccable the timing is of your post. I just bought a 3hp three phase lathe that I’m trying to figure out how to power up, VFD or rpc or motor swap. I suspect a VFD would be the cheapest way to go but I don’t know my way around those things. Your post about Invertek seems like a good possibility for me. Thank you.



VFD for sure. You have to also evaluate the the value of the features you gain with a VFD over a single phase solution. The only knock I have heard about Invertek's is they don't have a ton of analog/digital inputs, but they do sell modules for expansion. Think of an analog/digital input as a terminal that allows you to make the VFD do something. Turning on the lathe in FWD takes 1 input.  Turning on the lathe in REV takes another input. If you want to use a potentiometer for speed control, another input.

That said, the Invertek somewhat solves this by programming certain actions when triggering two  inputs at the same time.  For example, Input 1 On FWD; Input 2 On REV.  Input 1 + 2 simultaneously, FAST STOP. The way this is achieved is input 1 is a normally open (NO) limit switch (LS). Input 2 is the same. A lever on the apron moving one way triggers one of those NO LS. Moving the other triggers the other. The lever itself is unable to close both switch simultaneously. This is due to the lathe having cam lobes on the power shaft that trip either one or the other. Now the brake pedal, that has a third NO LS and it’s own cam. By running 1 wire to the terminal that controls ON FWD and another to the terminal that controls ON REV and then hooking those up to the limit switch on the brake, I’m able to connect a circuit between those two terminal simultaneously, resulting in the lathe stopping quickly. 

Now that I've done it, and recently, it would be no problem at all to get your started. Not sure how comfortable you are working in your load center, but I can take you all the way from the breaker to the VFD and down to the components, if you want.


----------



## matthewsx (Mar 19, 2022)

Pics or it didn‘t happen

Sounds like a great setup….

John


----------



## Ceej0103 (Mar 19, 2022)

matthewsx said:


> Pics or it didn‘t happen
> 
> Sounds like a great setup….
> 
> John



Bed time for now. I’ll post some tomorrow. 


Sent from my iPhone using Tapatalk


----------



## Ceej0103 (Mar 19, 2022)

matthewsx said:


> Pics or it didn‘t happen
> 
> Sounds like a great setup….
> 
> John



Here’s a teaser. I would have done a complete talking video, but my shop is so messy from focusing on the lathe build that I’m literally embarrassed.  I’m going to focus on getting my space back in order, then a more detailed video to follow. This is just me firing up the spindle from the apron controls and then ramping down the speed with the pot.  I then show you how I’ve replaced the old high voltage switches with 3 low voltage latching backlit push buttons, a key switch that controls main power to the VFD to lock down the machine and the 10K POT.  One button goes to work lights, one to coolant pump, one to siren in the house if I need my wife to bring me a sandwich and some chips.


----------



## matthewsx (Mar 19, 2022)

Nice work, need to go the extra step with my lathe….

john


----------



## detchells (Jun 2, 2022)

Your post was perfect for me as well; I just got a Precision Matthews 1236, and went with a 3-phase motor and VFD, an Invertek E3 the same as you. Taking the support number from your post, I called and spoke with a tech named Jared, and he very quickly understood what I was wanting to do and answered all my questions. I agree, they have fantastic tech support, it was *WELL* worth the higher price vs a Chinesium model!


Ceej0103 said:


> That said, the Invertek somewhat solves this by programming certain actions when triggering two  inputs at the same time.  For example, Input 1 On FWD; Input 2 On REV.  Input 1 + 2 simultaneously, FAST STOP. The way this is achieved is input 1 is a normally open (NO) limit switch (LS). Input 2 is the same. A lever on the apron moving one way triggers one of those NO LS. Moving the other triggers the other. The lever itself is unable to close both switch simultaneously. This is due to the lathe having cam lobes on the power shaft that trip either one or the other. Now the brake pedal, that has a third NO LS and it’s own cam. By running 1 wire to the terminal that controls ON FWD and another to the terminal that controls ON REV and then hooking those up to the limit switch on the brake, I’m able to connect a circuit between those two terminal simultaneously, resulting in the lathe stopping quickly.


I’m setting up my drive the same as yours, where Fwd + Rev at the same time will do a fast stop, but I’m a bit confused by your description: wouldn’t tying the brake switch to both fwd/rev inputs mean that any time one normal switch closed, the other inout would see the closure also? I’d think that you would need a couple of diodes to prevent that from happening. (Or maybe your brake switch is DPST?)


----------



## Ceej0103 (Jun 2, 2022)

detchells said:


> Your post was perfect for me as well; I just got a Precision Matthews 1236, and went with a 3-phase motor and VFD, an Invertek E3 the same as you. Taking the support number from your post, I called and spoke with a tech named Jared, and he very quickly understood what I was wanting to do and answered all my questions. I agree, they have fantastic tech support, it was *WELL* worth the higher price vs a Chinesium model!
> 
> I’m setting up my drive the same as yours, where Fwd + Rev at the same time will do a fast stop, but I’m a bit confused by your description: wouldn’t tying the brake switch to both fwd/rev inputs mean that any time one normal switch closed, the other inout would see the closure also? I’d think that you would need a couple of diodes to prevent that from happening. (Or maybe your brake switch is DPST?)



See if this helps. I’m not a double E so my electrical schematics may be pretty bad. I think you’re over complicating the circuit. Breaking it down to basics, you would have voltage at either the FWD or REV terminal on the VFD because the lathe is running. You would have no voltage at FWD if you’re in REV and no voltage at REV if you’re in FWD. Any wire connected to the FWD or REV terminal would also see voltage when the limit switch is closed because that’s essentially when the NO LS is doing, passing voltage through to the FWD or REV terminal. 

Ok so now we’ve established that one of the two, but not both of the terminals will have voltage. To initiate a fast stop, the VFD needs to see voltage on BOTH FWD and REV terminals simultaneously. If you run a lead from the FWD and REV terminals to opposite sides of a NO LS, one side of that NO LS will have voltage when the lathe is operating. By closing that LS, you’re creating a pathway/condition in which both FWD and REV are provided voltage simultaneously. This NO LS is your brake switch. 

When the brake is pressed, fast stop initiates and the lathe stops. The VFD will require that both the FWD and REV terminals are de-energized before the VFD will put power to the motor again. Because your apron lever is still in either FWD or REV, you have not met the reset condition and the VFD will not energize the motor. To reset, you just take the apron lever back to off and then back in to FWD/REV. This is a great safety feature. 

Sorry I didn’t use specific Invertek terminal numbers/etc. I’m out right now and don’t recall by memory what each terminal is named.


----------



## detchells (Jun 2, 2022)

Ceej0103 said:


> Ok so now we’ve established that one of the two, but not both of the terminals will have voltage. To initiate a fast stop, the VFD needs to see voltage on BOTH FWD and REV terminals simultaneously. If you run a lead from the FWD and REV terminals to opposite sides of a NO LS, one side of that NO LS will have voltage when the lathe is operating. By closing that LS, you’re creating a pathway/condition in which both FWD and REV are provided voltage simultaneously. This NO LS is your brake switch.
> 
> When the brake is pressed, fast stop initiates and the lathe stops. The VFD will require that both the FWD and REV terminals are de-energized before the VFD will put power to the motor again. Because your apron lever is still in either FWD or REV, you have not met the reset condition and the VFD will not energize the motor. To reset, you just take the apron lever back to off and then back in to FWD/REV. This is a great safety feature.


Ah! DUH, you're right, I was over-complicating it - or at least didn't realize that I could just use the voltage on one of the terminals to bridge to the other one. I was thinking in terms of the NO emergency stop switch connecting both to the +V, meaning that both would be tied to the same terminal. Your approach is super-simple, thanks!

(Hmm, OTOH the emergency-stop switch on the front panel of my lathe is currently an NC contact. I had been planning to just put this in series with the +V used to provide power to the FWD/REV contacts. Hitting the button would open the contact and stop the lathe, but only at the normal turn-off ramp rate. I'll see if the switch itself might actually be a SPDT so I can use the other side of it for the NO function. If not, I may need to add a relay or use a transistor, resistor and pair of diodes to invert the signal.)

Thanks again so much for the quick and insightful reply - I actually have a Masters in EE, but sometimes it's not how much you know, it's how you think ;-)


----------



## Ceej0103 (Jun 3, 2022)

detchells said:


> I'll see if the switch itself might actually be a SPDT so I can use the other side of it for the NO function. If not, I may need to add a relay or use a transistor, resistor and pair of diodes to invert the signal.)



Or just get a new switch that's NO and go from the NO brake switch in to the E-Stop switch. If your lathe is like mine, the brake cam/switch is over on the left of the machine near the motor and your E-Stop is over on that side of the machine, too.  A parallel configuration would mean each of the NO switches (e-stop/brake) would always have voltage on one side when the machine is operating and closing either of the switches would backfeed/bridge back to the VFD's DI1 or DI2 terminals thereby providing voltage to both DI1 and DI2 simultaneously.  I think I'm using Macro 5, which also includes analog input at DI4/AI1 for my POT. 

BTW, should have mentioned this prior. Fast Stop, at extremely high RPM, will likely cause over voltage errors. I know from experience. If you're running high RPM (1000+) you'll need to adjust your fast stop to not be so fast (play around until it doesn't give you an over voltage error). If that's not good enough, which 3 seconds isn't really good enough if an emergency occurs, you should grab a braking resistor.  This will allow you to make that stop near instant without hitting over voltage limits on the VFD.  Mark (user MKSJ) is the VFD wizard around here.  He recommended the following resistors for my unit. I'm using the 5 HP (Frame Size 3) VFD.  There's a table in the manual in section 9. Technical Data that tells you the Recommended Brake Resistance for each of their OptiDrive E3 VFD sizes. A call to the technical support line would get you that information rather quickly, as well. I'm sure mouser, the online store Mark recommended would also have the variant you require if you're not also using the 5HP VFD. 




			https://www.mouser.com/ProductDetail/TE-Connectivity-Holsworthy/TJT50033RJ?qs=Rv6LVDxB0Zqcy032uO625w%3D%3D
		




			https://www.mouser.com/ProductDetail/ARCOL-Ohmite/HS500-25R-J?qs=mAH9sUMRCtsW%252BvtMODs%252B8w%3D%3D
		


Let's see some pics of the setup! You show me yours and I'll show you mine


----------



## 7milesup (Jun 3, 2022)

@Ceej0103   Where did you purchase your Invertek VFD?


----------



## Ceej0103 (Jun 3, 2022)

7milesup said:


> @Ceej0103   Where did you purchase your Invertek VFD?



Amazon


----------



## detchells (Jun 4, 2022)

Ceej0103 said:


> Or just get a new switch that's NO and go from the NO brake switch in to the E-Stop switch. If your lathe is like mine, the brake cam/switch is over on the left of the machine near the motor and your E-Stop is over on that side of the machine, too.  A parallel configuration would mean each of the NO switches (e-stop/brake) would always have voltage on one side when the machine is operating and closing either of the switches would backfeed/bridge back to the VFD's DI1 or DI2 terminals thereby providing voltage to both DI1 and DI2 simultaneously.  I think I'm using Macro 5, which also includes analog input at DI4/AI1 for my POT.


My lathe doesn't have a brake pedal; I think just having the normal decel ramp time on the drive set to 3 or 4 seconds will be fine without having a separate brake switch. I want to use the current (NC) e-stop switch because it's one of those huge red locking pushbuttons that'll be harder to miss in a panic. I'm gonna pull the panel in a few minutes and see if it's actually SPDT inside or if I need to do something to invert its signal.


Ceej0103 said:


> BTW, should have mentioned this prior. Fast Stop, at extremely high RPM, will likely cause over voltage errors. I know from experience. If you're running high RPM (1000+) you'll need to adjust your fast stop to not be so fast (play around until it doesn't give you an over voltage error). If that's not good enough, which 3 seconds isn't really good enough if an emergency occurs, you should grab a braking resistor.  This will allow you to make that stop near instant without hitting over voltage limits on the VFD.


Yeah, I'd known about that. Your note here is very timely, though, as I've been waiting for Invertek to reply back about resistor sizing. I didn't realize they had a table in the manual; the printed copy just says to ask your supplier for a recc. At your suggestion, I looked at the PDF and found the resistor sizing info there.


Ceej0103 said:


> Mark (user MKSJ) is the VFD wizard around here.  He recommended the following resistors for my unit. I'm using the 5 HP (Frame Size 3) VFD.  There's a table in the manual in section 9. Technical Data that tells you the Recommended Brake Resistance for each of their OptiDrive E3 VFD sizes. A call to the technical support line would get you that information rather quickly, as well. I'm sure mouser, the online store Mark recommended would also have the variant you require if you're not also using the 5HP VFD.


Mine's the 3HP model, so it looks like 50 ohm is what I'll want.


Ceej0103 said:


> https://www.mouser.com/ProductDetail/TE-Connectivity-Holsworthy/TJT50033RJ?qs=Rv6LVDxB0Zqcy032uO625w%3D%3D
> 
> 
> 
> ...


Wow, those are beefy, at 500 watts :-0 Given that my machine is smaller (1.5HP motor), I think I can probably get away with 200-250W.


Ceej0103 said:


> Let's see some pics of the setup! You show me yours and I'll show you mine


Happy to! I have some figuring out, wiring and packaging to get sorted before it'll be fit for public sharing 
I've got a steel control box that I'm gonna mount a line filter, the speed pot and a type-B circuit breaker in, and mount both it and the drive on the sheet metal apron between the lathe mount pedestals. It's tucked well under the chip tray, so I think would be safe from coolant, etc, and I'm not likely to bump it. I'll probably make a separate sheet metal shield to go above the drive itself as added protection. 

(I dunno though, I need to make some sort of a mount for the DRO, might somehow combine that with drive and control panel. Really, though, I'd only need the speed pot and a tach readout up top, so that may be what I do. I'm staring at it and pondering, with the knowledge that I'll almost certainly end up redoing things once I start actually using the lathe  I need to look at some pics and see how people typically mount DROs for maximum convenience...)

I just got the lathe up onto its stand and leveled the other day, am still cleaning the anti-rust goo off of it, so it'll be a little bit yet 

Thanks again for all the info!


----------



## detchells (Jun 4, 2022)

7milesup said:


> @Ceej0103   Where did you purchase your Invertek VFD?


FWIW, my own 3HP/2.2KW unit came from DrivesWarehouse. $355 including shipping, but it's a size smaller than @Ceej0103's model.


----------



## Dabbler (Jun 4, 2022)

If you like to home brew, you can use a 50 ohm stove element as a braking resistor.   They are rated at 800, 1000, and 1200 watts.  Mine cost 40$ CDN.


----------



## jaredmurphy621 (Jun 9, 2022)

Hi All,

When it comes to understanding how to wire the terminal strip of the Invertek Optidrive E3, I recommended first learning the Macro Functions reference tables from the user guide. Once you wrap your head around how to read it, the rest is straight forward.


----------



## jaredmurphy621 (Jun 9, 2022)

The diodes would be necessary without the mechanical interlocks provided by the cams. This is at least what it sounds like. An alternative to diodes is to create your own interlock with extra contacts on each of the pilot devices should they be of that type.


----------



## MattyP (Nov 1, 2022)

Ceej0103 said:


> Amazon



Wonder if they dropped their store off Amazon. I'm not seeing anything from Invertek on there.



detchells said:


> FWIW, my own 3HP/2.2KW unit came from DrivesWarehouse. $355 including shipping, but it's a size smaller than @Ceej0103's model.



Much appreciated on the DrivesWarehouse recommendation. After striking out on Amazon, I started going through Invertek's website to see if I could find a local contact here in MN. I did, but after contacting that company, I was given an estimated quote of $900 for the exact model that shows $355 on DrivesWarehouse.


----------



## detchells (Nov 1, 2022)

MattyP said:


> Much appreciated on the DrivesWarehouse recommendation. After striking out on Amazon, I started going through Invertek's website to see if I could find a local contact here in MN. I did, but after contacting that company, I was given an estimated quote of $900 for the exact model that shows $355 on DrivesWarehouse.


Glad it helped! Wow, $900 locally? That's highway robbery! DrivesWarehouse tech support was also very helpful, the tech I spoke with really knew the drives and applications inside and out. He gave me everything I needed to know in just one ~5 minute call.

BTW, relative to one of my previous questions, I ended up ordering a beefy 50-ohm brake resistor and have found that it's really not adequate for stopping the lathe quickly when spinning at high speed (1,000+ rpm) with the 8" chuck on it; I get an over-volt error. I'm sure it'd stop the motor pretty quick if it was just turning a fan blade or blower, but all the mass of the chuck and gearing is just too much for it; I think I should have gone with a 30-40 ohm instead. I'm debating whether to buy another resistor or just live with it (it'll still ramp down fairly quickly, but OTOH, if it's an emergency, I'll want it to stop *right now*.)


----------



## hman (Nov 1, 2022)

Wiring a second 50 ohm resistor in parallel would give you 25 ohms.


----------



## mksj (Nov 1, 2022)

You need to look at the minimum allowed ohms for a braking resistor per the manufacturer. Going to lower ohms then specified will cause permanent damage to the VFD.


----------



## detchells (Nov 1, 2022)

hman said:


> Wiring a second 50 ohm resistor in parallel would give you 25 ohms.


Yes of course, I'd like to avoid the expense of another industrial resistor if I can though


----------



## detchells (Nov 1, 2022)

mksj said:


> You need to look at the minimum allowed ohms for a braking resistor per the manufacturer. Going to lower ohms then specified will cause permanent damage to the VFD.


Absolutely, that's next on my list 

(Something I need to investigate though: If I program a very fast ramp-down as the default, it seems to stop the chuck *very* quickly without complaint - although I haven't tried that at high RPMs yet. But programming the same ramp-down for the emergency stop (I forget, think it's parameter 24 on the Invertek), it doesn't seem to stop nearly as quickly. I'm probably misunderstanding the settings or have some other parameter set in a way that interferes. It's running for now and stops reasonably quickly, figuring out faster Estop is a bit lower priority.)


----------



## Dabbler (Nov 1, 2022)

@detchells  The emergency stop won't ramp down the chuck using the e-braking resistor.  At least not on TECO  and msc offshore VFDs.  the emergency stop top cuts off all power and prevents an electrical meltdown...


----------



## detchells (Nov 1, 2022)

Dabbler said:


> The emergency stop won't ramp down the chuck using the e-braking resistor.  At least not on TECO  and msc offshore VFDs.  the emergency stop top cuts off all power and prevents an electrical meltdown...


Ah, interesting.

(pause)

Hmm, it seems that the Invertek in fact should be using the fast-stop ramp time when the emergency stop button is pressed, as it does have an option for that. I have the macro functions-terminal mode (P-15) set to 5, and in this mode, bridging digital inputs DI1 and DI2 should apply the Fast Stop ramp time. 

I just tried setting a fast ramp for the normal turn-off though, and it didn't slow quickly like it used to either. Formerly, this would bring the chuck to a very abrupt stop unless it was spinning quite fast, in which case it'd trip with an overvolt error. I'm suspecting I have a bad brake transistor in the VFD. - Or it for some reason doesn't like the resistor that's attached; it seems like it's had this behavior since I first connected the resistor. Next step is to try removing the resistor and see if it regains its former functioning, and if that works, checking the resistor to see if it's shorted or open.


----------



## mksj (Nov 1, 2022)

First one needs to understand what the electronic braking does and how it is applied. When one sets a braking time, it sets the slope of the braking rate based on the time (say 2 seconds) and the maximum Hz (say 60Hz). If you are running the motor at 30 Hz it will stop in 1 second, and at 15 Hz in 0.5 seconds. It is not 2 seconds for any Hz.  If you are running the lathe at maximal speed it would take twice as long to stop as it would from 1/2 maximal speed (50% on the speed pot). There is also how the braking is applied, so there is linear and S-Curve, and these can effect the slope of the braking during deceleration. An S curve will have a steeper slope at the center, this may exacerbate an over voltage error, I find a linear slope on braking to give the most consistent stopping. The Invertek VFD offers no control over how the braking is applied. If you get an over voltage buss error then you are braking too fast. If you are spinning a big chuck at high speed then it may cause an over voltage error and the VFD will go into a free run mode with no braking. Higher end VFD's have parameters which will prevent this from happening by adjusting the braking rate if too high so an over voltage error does not occur. Use of DC injection does not effect braking until very low speed, so it is used to bring high momentum systems to a stop at the end of their braking.

P-04 should be something like 2 seconds. P-24 allows a second ramp time (fast stop) input, but this only applies if it is set to a time less than P-04, so say 1.5 seconds or maybe 1 second. Braking resistor for 2 Hp unit is 100 ohms, 3 Hp unit is 50 ohms. There are different trad offs as to the resistor size, but maximal braking is achieved with a lower resistance, but less frequent repeat stops. This is outlined for other VFD drives.

Teco L510 does not support an external braking resistor. The emergency stops and braking for power loss are usually programmable, but depends on the VFD. In general, although the Invertek is relatively easy to setup, I do not use them for lathes because of limited programmable inputs as well as very limited programming ability.

Invertek Optidrive E3


----------



## detchells (Nov 3, 2022)

mksj said:


> First one needs to understand what the electronic braking does and how it is applied. When one sets a braking time, it sets the slope of the braking rate based on the time (say 2 seconds) and the maximum Hz (say 60Hz). If you are running the motor at 30 Hz it will stop in 1 second, and at 15 Hz in 0.5 seconds. It is not 2 seconds for any Hz.


Ah, interesting, I didn't know that. It's based on the number of line power cycles vs time. Thanks!


mksj said:


> There is also how the braking is applied, so there is linear and S-Curve, and these can effect the slope of the braking during deceleration. An S curve will have a steeper slope at the center, this may exacerbate an over voltage error, I find a linear slope on braking to give the most consistent stopping. The Invertek VFD offers no control over how the braking is applied. If you get an over voltage buss error then you are braking too fast. If you are spinning a big chuck at high speed then it may cause an over voltage error and the VFD will go into a free run mode with no braking. Higher end VFD's have parameters which will prevent this from happening by adjusting the braking rate if too high so an over voltage error does not occur. Use of DC injection does not effect braking until very low speed, so it is used to bring high momentum systems to a stop at the end of their braking.



I think I only got the over-volt error when I was running it without the braking resistor. I haven't seen it recur, even when stopping quickly from pretty high speed.

I might want to play with DC injection, it's a function on the Invertek (P-32, P-58 and P-59) - or maybe not, see my parting comment below.

I think what I was interpreting as faulty braking was just that its effect drops off at very low frequencies, when the motor is still spinning, albeit slowly. With a heavy chuck, it tends to "coast" a bit. I tried taking the chuck off, and the spindle on its own didn't tend to coast as much. 

It turns out I was running the drive at a very low frequency (only 20 Hz), thinking I was being cautious by not having things spinning so fast. But at such a low RPM, I was likely close to the regime where electrical braking doesn't work as well. As noted below, it works pretty well at 60 Hz.

(An unimportant point, but I think I now understand another behavior I observed: If I program a very short stop time, it can actually take longer for the motor to stop turning than with a somewhat longer one. My interpretation is that the ramp-down is so fast that the chuck still has more kinetic energy left when the frequency drops below the effective control range.)

That's interesting about the more advanced drives letting you control the braking curve, and having the smarts to back off in an over-voltage condition; it makes a lot of sense, and I can imagine there are a lot more complex options that can be programmed for special industrial uses. This is definitely a basic application not needing all that, but it's interesting to read about  



mksj said:


> P-04 should be something like 2 seconds. P-24 allows a second ramp time (fast stop) input, but this only applies if it is set to a time less than P-04, so say 1.5 seconds or maybe 1 second. Braking resistor for 2 Hp unit is 100 ohms, 3 Hp unit is 50 ohms. There are different trad offs as to the resistor size, but maximal braking is achieved with a lower resistance, but less frequent repeat stops. This is outlined for other VFD drives.


Wow, thanks for going so far as to look up the Invertek manual! 

Yeah, mine is a 3HP unit, running a 2HP motor. The resistor I bought is 47 ohms, which I figured was close enough. I didn't remotely need the wattage, but a 400W unit was cheaper than less burly ones. (I could have gone a lot cheaper with a regular power resistor, but I wanted the isolated case for safety.) After multiple fairly high-speed stops, the resistor is still cool to the touch.


mksj said:


> Teco L510 does not support an external braking resistor. The emergency stops and braking for power loss are usually programmable, but depends on the VFD. In general, although the Invertek is relatively easy to setup, I do not use them for lathes because of limited programmable inputs as well as very limited programming ability.


I'm glad I got the Invertek then. It sounds like Tecos might be more programmable, but I like having the braking resistor and it's already way more programmable than I need   

Bottom line on my issue, I was running the drive at such a low frequency that the electronic braking wasn't very effective and left a lot of momentum in the spindle and chuck at the point that the frequency dropped so low that it lost control of the motor. At 60Hz it stops pretty close to the time programmed (whether in P-4 or P-24) but still has some residual momentum. I might try experimenting with DC injection for the Fast Stop, but proceed carefully. The Invertek programs the DC current as a percentage of running current, though, and I'd think even 100% current (~9 amps) for less than a second couldn't do too much to the unit - and I'd start with the minimum of 20%.

OTOH, maybe I should just leave well enough alone. Stopping the motor in ~1 second is pretty darn fast, and I don't want to over-stress the gearing by having the motor slam everything to an instantaneous stop.

Thanks again for taking the time to leave such a complete and detailed answer, I really appreciate it!


----------

