VFD in the CNC poo'd the bed

[precisionworks]

Looked into the ACtech. To match up the amperage I would need a 15HP drive.

A few posts back you mentioned that the motor is 5hp continuous and 7.5hp max. Before you decide on the brand & model of VFD you'll need to consider what you want the machine motor to do.

If you need not more than 5hp continuous then any of the 5hp single phase VFD's will work fine, as will any 10hp VFD unless it has phase loss detection. TECO, Hitachi, ACTech, Siemens, Toshiba, Yaskawa, Mitsubishi, Baldor, ABB, etc. are all good candidates.

If you need a drive to support 7.5hp the game changes abruptly. No 5hp 1-ph or 10hp 3-ph drive will supply the amps/watts necessary to run a 7.5hp motor except for a brief time (which varies by brand & model). Running a 7.5 hp motor requires a 15hp 3-ph drive & there's no way to work around that.

Only thing left is to figure out if I can use my existing braking resistors or if I will have to buy new ones.

Tech support should be able to figure out exactly what the drive needs to function properly.

 

[sortafast]

A few posts back you mentioned that the motor is 5hp continuous and 7.5hp max. Before you decide on the brand & model of VFD you'll need to consider what you want the machine motor to do.

If you need not more than 5hp continuous then any of the 5hp single phase VFD's will work fine, as will any 10hp VFD unless it has phase loss detection. TECO, Hitachi, ACTech, Siemens, Toshiba, Yaskawa, Mitsubishi, Baldor, ABB, etc. are all good candidates.

If you need a drive to support 7.5hp the game changes abruptly. No 5hp 1-ph or 10hp 3-ph drive will supply the amps/watts necessary to run a 7.5hp motor except for a brief time (which varies by brand & model). Running a 7.5 hp motor requires a 15hp 3-ph drive & there's no way to work around that.

While I don't anticipate running the mill to full load, I have run it pretty hard. I was running it really hard right before the VFD croaked. Was pulling 70ipm at 3200rpm in aluminum with a carbide aluminum rougher with pretty good amount of material being removed (like .375" DOC at .2" wide on a 1/2" endmill). I think this was taxing the machine more than it every really had been before. Anyway, I am not looking at keeping this machine long term. I would like to upgrade to a better machine with a 15-20 tool ATC. But this will have to get me by until I get there. So I want to be able to have a drive in this machine that will be as close to the factory drive as possible. I don't need a lot of fancy features, just need it to be able run as it used to. From my limited knowledge and looking, the SMV drive might not have enough inputs and out puts. My machine controls the VFD via analog signals from what I can gather. I do not believe there are any digital signals coming from the cnc control. I have a list of what is needed, but I do know that the Teco has everything I need. I am less certain about the ACTech. Also, I am basing the HP rating on the amps required. In the parameters for my dead drive it put the max amps at 32. The motor is rated up to 39A but I think they derate it for longevity. The 10hp SMV will go to 28A so I think that would be acceptable. But if it lacks the inputs that I need I would rather get the Teco. But then again I found a 10hp SMV for $540 delivered which very much appeals to my inner cheapskate. I really need to get this all figured out and soon. Should have most all of the $$ by next week and need to get this done ASAP as I was just at the front end of a rather large and very critical run of parts.

Tech support should be able to figure out exactly what the drive needs to function properly.

For the Teco I know I need a 780W 200ohm braking resistor. What I have in my mill is an array of 4 very large 100ohm resistors that I am having trouble locating the wattage rating. If I can make what I have work with the new drive I will be very happy as it would save me some coin. Not sure if it will or not though. I need to tear it apart further to see if I can find a part # to reference or something.

 

[precisionworks]

... the SMV drive might not have enough inputs and out puts. My machine controls the VFD via analog signals from what I can gather...

The drive has 4 digital inputs (1 run/stop and 3 programmable), a Form A digital relay output switch, will accept both 0-10 VDC, 2-10 VDC and 4-20 mA analog inputs & will also supply a 0-10 VDC analog output. The drive also has a 10 VDC potentiometer reference, a 12 VDC 20 mA power supply for digital inputs, and a 12 VDC 50 mA supply. It also supports PID loop control.

Parameter P150 lists the analog selections for 0-10 VDC control & 2-10 VDC control. A 2-10 VDC signal can be converted to 4-20 mA with a total circuit impedance of 500 Ω. Tech support can confirm whether the SMV control will work in your application.

FWIW most of the analog controls I see are either 0-10 or 4-20.

0 None
1 0-10 VDC Output Frequency
2 2-10 VDC Output Frequency
3 0-10 VDC Load
4 2-10 VDC Load
5 0-10 VDC Torque
6 2-10 VDC Torque
7 0-10 VDC Power (kW)
8 2-10 VDC Power (kW)
9 Network Controlled Requires optional communication module

 

[sortafast]

The drive has 4 digital inputs (1 run/stop and 3 programmable), a Form A digital relay output switch, will accept both 0-10 VDC, 2-10 VDC and 4-20 mA analog inputs & will also supply a 0-10 VDC analog output. The drive also has a 10 VDC potentiometer reference, a 12 VDC 20 mA power supply for digital inputs, and a 12 VDC 50 mA supply. It also supports PID loop control.

Parameter P150 lists the analog selections for 0-10 VDC control & 2-10 VDC control. A 2-10 VDC signal can be converted to 4-20 mA with a total circuit impedance of 500 Ω. Tech support can confirm whether the SMV control will work in your application.

FWIW most of the analog controls I see are either 0-10 or 4-20.

0 None
1 0-10 VDC Output Frequency
2 2-10 VDC Output Frequency
3 0-10 VDC Load
4 2-10 VDC Load
5 0-10 VDC Torque
6 2-10 VDC Torque
7 0-10 VDC Power (kW)
8 2-10 VDC Power (kW)
9 Network Controlled Requires optional communication module

yeah, I am going to call on monday and get all of the details. This whole mess is making my brain hurt. On top of all this I have some other business related things that just came up that have a major potential to be a headache. Hopefully this coming week starts out a lot better than that last one did. Ugh...

 

[sortafast]

A few posts back you mentioned that the motor is 5hp continuous and 7.5hp max. Before you decide on the brand & model of VFD you'll need to consider what you want the machine motor to do.

If you need not more than 5hp continuous then any of the 5hp single phase VFD's will work fine, as will any 10hp VFD unless it has phase loss detection. TECO, Hitachi, ACTech, Siemens, Toshiba, Yaskawa, Mitsubishi, Baldor, ABB, etc. are all good candidates.

If you need a drive to support 7.5hp the game changes abruptly. No 5hp 1-ph or 10hp 3-ph drive will supply the amps/watts necessary to run a 7.5hp motor except for a brief time (which varies by brand & model). Running a 7.5 hp motor requires a 15hp 3-ph drive & there's no way to work around that.

Tech support should be able to figure out exactly what the drive needs to function properly.

Haven't heard back from ACTech about the SMV working for this application. And the more I look through the manual the more it looks like it won't work with out some serious doing that far exceed what I want to put into it. I am looking very strongly at the Teco at this point. It looks like the easiest to wire in with what I have for connections from the controller and with what the old Drive was set up with. I am just torn as to the size of the unit to get. Right now I am getting my 3ph from a 7.5hp American Rotary RPC head unit with a used 7.5hp motor. Works pretty good. So I am not using the VFD to go from 1ph -> 3ph.

So I am looking at the #'s on the teco brochure here and I am torn between the 7.5hp and the 10hp 230v 3ph MA7200's, part numbers MA7200-2007-N1 and the MA7200-2010-N1. Not sure what the deal is with Variable Torque vs Constant Torque for this application (Tree 325J cnc knee mill). I am seeing that the VFD size should be based on the FLA of the motor. FLA of motor are listed at 39A . The Parameters list the Amps being limited to 32A but the plate on the back of the machine says the max current draw is 20A, so I am a bit confused. Since I am being told constant torque is the way to go, With the 7.5hp MA7200 the CT amps are 24A and VT are 32A. With the 10hp MA7200 its 32A for both CT and VT. I did some rough calcs for some of the machining I do and it says that I shouldn't be over 3hp for even the nastiest machining I currently do or plan on doing. Due to chip containment, I doubt I would push much harder than I already am. So, with the De-rated Amps of the 7.5HP MA7200 would I have issues? That is where I am stuck. With lower amps being input, would that just lower the amount of Torque/Horespower I would have? Or is there some other negative consequence that I am missing there? I don't want to end up constantly faulting out the drive when machining hard, and I also don't want to have to go out and buy the 10hp unit after the fact. Limited funds + limited VFD installation and application knowledge = much headaches. I just want to get this right the first time and not have to do it again.

 

[precisionworks]

You may want to post your question in the Phase Converter & VFD Section on PM.

Regarding hp requirements, try figuring a 3" face mill, 6 inserts, .125" DOC, 800 sfpm, in 4140HT, running all the ipm the machine can stand. I've runs Bridgeport's with 3hp motors us those parameters & the ipm is limited by the low hp & torque.

It all depends on what you machine & how it's set up. If time isn't an issue & smaller DOC or lower ipm is acceptable the smaller motor may be adequate.

 

[Jakefreese]

Variable torque is often fine in milling machines as you are not changing speeds while your engaged in cutting. Constant torque is often required when speeds and loads are dynamically changing (material positioning such as cranes and mobile equipment).

So the old drive parameters limited the current to 32a? How many kW was the spindle?

When we run into challenges on drive selection control concepts in Dallas has been our go to. I deal with crane, water pump, conveyor, equipment drives. I have limited experience in the fabrication tool vfd design.

 

[sortafast]

I already x-posted this to PM. I like to spread the love around .

You may want to post your question in the Phase Converter & VFD Section on PM.

Regarding hp requirements, try figuring a 3" face mill, 6 inserts, .125" DOC, 800 sfpm, in 4140HT, running all the ipm the machine can stand. I've runs Bridgeport's with 3hp motors us those parameters & the ipm is limited by the low hp & torque.

It all depends on what you machine & how it's set up. If time isn't an issue & smaller DOC or lower ipm is acceptable the smaller motor may be adequate.

This is a semi-open CNC Knee mill. I doubt I will ever need to run a 3" facemill like that in steel. I mostly work in aluminum as that is easy to machine and my droplet coolant system works great for it. I am planning on more fully enclosing this mess and getting flood coolant so I *could* potentially cut the steel like that, but I don't know if/when I will. I don't really have a need to at this point, and if I did, I would take it over to my buddy's shop who is set up for cutting steel. At the end of the day though, I would much rather have 2 machines one for Aluminum and one for steel. Would make cleaning them up easier :naughty:

Variable torque is often fine in milling machines as you are not changing speeds while your engaged in cutting. Constant torque is often required when speeds and loads are dynamically changing (material positioning such as cranes and mobile equipment).

So the old drive parameters limited the current to 32a? How many kW was the spindle?

The spindle is 5.5kw max and 3.9kw continuous (i think its 3.9, I know its somewhere around there). Voltages go from 21V min to 160v max as indicated by the parameter sheet that I have for the old drive. Max Amps listed on the motor plate were 29A Cont and 39A max with a 200v max for the motor. It seems that everything has been toned down from max by 10-20% (max RPM for the motor is 8k while the machine runs it to a max of 7k on the RPMs and the Max Volts in the controller are 160v vs the 200v max, etc). I am thinking with this de-rating so to speak I think I am on the border of the 2 drives. I am all about saving money here as I have a Pistol suppressor I still need to pay the tax stamp on, so anything I can save $$$ wise here would be very nice indeed.

 

[precisionworks]

Variable torque is often fine in milling machines as you are not changing speeds while your engaged in cutting. Constant torque is often required when speeds and loads are dynamically changing (material positioning such as cranes and mobile equipment).

Variable torque (or V/Hz) drives work best on motor loads where the required torque decreases as load rpm decreases. Pumps & fans are two examples of decreasing speed/decreasing torque loads. These drives cost less for a number of reasons including more simple control algorithms, less powerful µP chips, lower wattage rated components, etc.

Constant torque (or vector) drives are designed to maintain 100% torque at motor speeds down to 0 rpm. These are most often chosen for machine tool speed control because they let the user choose the spindle speed most appropriate for the material.

 

[sortafast]

Well I couldn't wait to raise the extra $$ so I got the 7.5hp VFD. Hopefully it works for what I need, but I think it will. Got the MA7200 and the corresponding brake resistor from Factorymation.com. Hopefully it shows up next week sometime so I can get back to work.

 

[precisionworks]

The 7.5hp model will be fine as long as the motor load is 3.75hp or less on a continuous run. All currently manufactured drives are NEC-approved as overcurrent protection devices so if the load exceeds drive capacity the drive will fault out, just like a molded case circuit breaker.

The MA7200 is rated at 150% over current for 1 minute & that allows pushing the motor load up to 5.6hp in short bursts. Thermal sensors in the drive constantly monitor component temp & the drive will fault out on over temp if pushed too hard for an extended time. Worst case is that you may need to reduce DOC or IPM on some ops.

 

[sortafast]

I don't think I have ever gone above 3hp of use on my spindle, and even then when I did come close it was probably when I was crashing it. With the calc's I ran for most of the cutting I am doing, the most I saw was a 2.8hp requirement. So I am thinking this thing will work for now. IF it doesn't, I will just save some pennies and buy its big brother if/when the time comes.

 

[sortafast]

Ok, got everything in and programmed and did my first tests with the spindle. Got full control of the motor via the Dynapath controller. Very happy. Had some issues with some parameters, but it was just stupid oversight from working too late at night on it. Changed a couple parameters having to do with motor overload faults and we are in business. Hopefully things will quiet down around here and I will get some time to see how it really performs.

On a side note, does anyone know how to set up the braking/decel times for the drive and the huge braking resistor? I don't want to fry things here but I would like to make my decel/stop times as short as possible so that I can go from cut to cut a lot faster.

 

[precisionworks]

The quick answer is to start with a long decel time like 5 seconds. If that doesn't fault try 4, 3, 2, 1, .5, .25, .125, etc. Until it faults out. Then increase time slightly until there's no fault.

 

[sortafast]

That was my thought on it. The factory parameter from the old drive was set at 10 seconds so I think going to 5 or something isn't out of the question. I just don't want to stuff too much heat into the cabinet from that resistor. But I am adding a couple fans to really throw some air throw the cabinet to keep things happy.