2 Speed Motor - VFD Best Practice

I am finishing up a VFD install on a Howa Sangyo 1500 and looking for advice on the 2-speed motor wiring “best practice”. I am not looking for a how to or a what is easiest, but what is the best way to tackle the 2-speed motor or what are the cons and benefits of the 2 options?

The VFD used is a Fuji Frenic Micro drive and is 2 motor capable. I currently have all the external controls properly wired including the foot brake coast to stop and hand brake decelerate to stop thanks to some posts by Motion Guru and JST. The motor being driven is a Fuji MRA 2135A if that means anything; it is a 2.8/5.5 kW 8/4 pole dual voltage 2 speed motor with a thermister. I currently have the VFD wired to the high-speed windings and achieve the low-speed setting using the multistep frequency commanded to 30hz through the x3 terminal.

Reading other posts, it seems this is the common way to wire a motor such as this, but I have not read much about the other option; using the 2-motor function of the drive to power a set of contactors connected to both the high and low speed windings. I understand I will see the same motor power at 30hz on the high windings as 60hz on the lower windings, but is there any other benefit to running the low windings at 60hz vs the high windings at 30hz?

My biggest interest in this configuration is that at the factory carrier frequency setting of 2khz the sound at 30hz motor speed is pretty terrible. When maxed out to 16khz carrier frequency it is much better but still noticeable without much gain beyond 12khz, where I currently have it set. At 60hz motor speed the carrier frequency does not make much difference, it is relatively quiet across the range when running both the low speed and high-speed windings. The other benefit I can see is being able to set distinct motor parameters and accel/decel speeds; currently it is just half that of the 60hz settings. I already have the contactors, so hardware is not a consideration.

Also, is 12khz a "motor safe" carrier frequency? I have not found a clear answer to this other than too low can cause more issue than too high as far as the motor is concerned, the neighbors ham radio be damned.

Thanks
Mike

MountaineerMiner said:

I am finishing up a VFD install on a Howa Sangyo 1500 and looking for advice on the 2-speed motor wiring “best practice”. I am not looking for a how to or a what is easiest, but what is the best way to tackle the 2-speed motor or what are the cons and benefits of the 2 options?

The VFD used is a Fuji Frenic Micro drive and is 2 motor capable. I currently have all the external controls properly wired including the foot brake coast to stop and hand brake decelerate to stop thanks to some posts by Motion Guru and JST. The motor being driven is a Fuji MRA 2135A if that means anything; it is a 2.8/5.5 kW 8/4 pole dual voltage 2 speed motor with a thermister. I currently have the VFD wired to the high-speed windings and achieve the low-speed setting using the multistep frequency commanded to 30hz through the x3 terminal.

Reading other posts, it seems this is the common way to wire a motor such as this, but I have not read much about the other option; using the 2-motor function of the drive to power a set of contactors connected to both the high and low speed windings. I understand I will see the same motor power at 30hz on the high windings as 60hz on the lower windings, but is there any other benefit to running the low windings at 60hz vs the high windings at 30hz?

My biggest interest in this configuration is that at the factory carrier frequency setting of 2khz the sound at 30hz motor speed is pretty terrible. When maxed out to 16khz carrier frequency it is much better but still noticeable without much gain beyond 12khz, where I currently have it set. At 60hz motor speed the carrier frequency does not make much difference, it is relatively quiet across the range when running both the low speed and high-speed windings. The other benefit I can see is being able to set distinct motor parameters and accel/decel speeds; currently it is just half that of the 60hz settings. I already have the contactors, so hardware is not a consideration.

Also, is 12khz a "motor safe" carrier frequency? I have not found a clear answer to this other than too low can cause more issue than too high as far as the motor is concerned, the neighbors ham radio be damned.

Thanks
Mike

Click to expand...

Refreshing to see someone doing "the rightest stuff" rather than the "easiest". Both windings are "paid for, already", why not USE them for a better match to the tasking?

You seem to have it all covered, as I'm presuming you have power and winding selection switching "associated" in some manner so as to NOT swap windings on the fly in a manner that challenges the VFD's survival?

I THINK all I would add is ... a "true sine wave" dv/dt filter (or "so they THINK it is!) to both reduce your annoying acoustics AND more important, really, reduce the unwelcome effects of carrier frequency and switching artifacts on the motor.

Your manual probably has a section for selection by specifications, ELSE calculating the parameters. Could was you even need TWO, one optimized for each set of windings?

Pass.

I no longer own any VFD not built-in to major appliances. Which I have "too many" of. Some "Ham", but a lot more cash invested in frozen steak and seafood!

Fuggabancha "radios"!

Accordingly, the three (Emerson) TCI "Sine-Guard" dv/dt filters here are "belt and braces" extra care to keep a Phase-Perfect mannerly enough to not mess up my fridges, microwave ovens, washer & dryer, routers, and laptop confus - ummm... "con PUTA s."

Sine-Guard's are typically about $50 to $100 used, $75 or so on average, GE-FANUC et al sometimes cheaper.

Zoro has economical Weigmann "NK" (no knockout) suffix make-yer-own-hole NEMA boxes deep enough to house them. No ugly holes to plug unless you want a screen-plug as vent in the sides rather than easier venting in the cover plate.

"3CW" ..and carry-on with the good work!

Montani Semper Liberi!

MountaineerMiner said:

I am finishing up a VFD install on a Howa Sangyo 1500 and looking for advice on the 2-speed motor wiring “best practice”. I am not looking for a how to or a what is easiest, but what is the best way to tackle the 2-speed motor or what are the cons and benefits of the 2 options?

The VFD used is a Fuji Frenic Micro drive and is 2 motor capable. I currently have all the external controls properly wired including the foot brake coast to stop and hand brake decelerate to stop thanks to some posts by Motion Guru and JST. The motor being driven is a Fuji MRA 2135A if that means anything; it is a 2.8/5.5 kW 8/4 pole dual voltage 2 speed motor with a thermister. I currently have the VFD wired to the high-speed windings and achieve the low-speed setting using the multistep frequency commanded to 30hz through the x3 terminal.

Reading other posts, it seems this is the common way to wire a motor such as this, but I have not read much about the other option; using the 2-motor function of the drive to power a set of contactors connected to both the high and low speed windings. I understand I will see the same motor power at 30hz on the high windings as 60hz on the lower windings, but is there any other benefit to running the low windings at 60hz vs the high windings at 30hz?

My biggest interest in this configuration is that at the factory carrier frequency setting of 2khz the sound at 30hz motor speed is pretty terrible. When maxed out to 16khz carrier frequency it is much better but still noticeable without much gain beyond 12khz, where I currently have it set. At 60hz motor speed the carrier frequency does not make much difference, it is relatively quiet across the range when running both the low speed and high-speed windings. The other benefit I can see is being able to set distinct motor parameters and accel/decel speeds; currently it is just half that of the 60hz settings. I already have the contactors, so hardware is not a consideration.

Also, is 12khz a "motor safe" carrier frequency? I have not found a clear answer to this other than too low can cause more issue than too high as far as the motor is concerned, the neighbors ham radio be damned.

Thanks
Mike

Click to expand...

I would think switching between the two sets of motor windings is straightforward,
other than three issues:

- you only want one set of windings connected any any given time
- you never want to disconnect motor windings from the VFD when the motor is turning
- if power is lost while the spindle is turning, something sensible happens (i.e. contactor coils are de-energized, what happens?)

So if you're up for designing some control wiring to make than happen, that would be doable?

-Phil

Brandenberger said:

I would think switching between the two sets of motor windings is straightforward,
other than three issues:

- you only want one set of windings connected any any given time
- you never want to disconnect motor windings from the VFD when the motor is turning
- if power is lost while the spindle is turning, something sensible happens (i.e. contactor coils are de-energized, what happens?)

So if you're up for designing some control wiring to make than happen, that would be doable?

-Phil

Click to expand...

Surely.

As with MOST challenges, it is an existing need, already has more than one workable solution.

Example: Because certain classes of other-than "4Q" SCR-reversed DC Drives are not happy with instant REVERSING, KB-Penta specifies an ignorant third-party DPDT TOGGLE switch... that is built with a "chicane" in the physical assembly. To slow-down the speed at which a human hand can guide the toggle & associated contacts through the "gate". So it is not ABLE to switch "too fast" between one mode and the next.

Exact OPPOSITE of a "Hurst" 4-on-the-floor speed-shifter, IOW.

A VFD's "built-in" remote-able controls, external "ice-cube" relays, solid-state switches, heavy power contactors?

All that control and power "logic" is a separate game.

The key player was simply an off-the-shelf retarded switch under the human hand. Literal "dumb as a box of rocks" solution ... and no complex, fragile, short-lived solid-state timers involved!

ISTR I paid Galco all of $35 bucks for my ones? Not as cheap as "ordinary" toggle switches, but still.. cheap enough.

Standard size and hardware. Mount in the same simple hole, fit the same "hexane" synthetic rubber-booties to keep coolant out, take standard "slap-down lift covers. "etc."

No further engineering required.

Not until Bubba-the-crunt grows frustrated with a "clumsy" switch, proudly replaces it with an "instant-fratrification" speed-switcher.. and blows the electronics directly into the ninth level of Hell!

You'd have to know human nature?

Although the Fugi MRA is dual voltage, are you sure the motor has two separate windings rather than a Dahlander connection that disengages four poles ? If the motor is a Dahlander, the need to bridge three wires on one speed makes using a vfd more complicated as there needs to be a way to jump the three leads. Others here may have a solution but knowing what type of two speed motor you have is the first step. Dave

beckerkumm said:

Although the Fugi MRA is dual voltage, are you sure the motor has two separate windings rather than a Dahlander connection that disengages four poles ? If the motor is a Dahlander, the need to bridge three wires on one speed makes using a vfd more complicated as there needs to be a way to jump the three leads. Others here may have a solution but knowing what type of two speed motor you have is the first step. Dave

Click to expand...

If he only HAS four, then its two poles or four, probably "only"?

But even if it WERE more complex? The VFD only needs to be "told how to act" as far as selecting which one of two load characteristic "sets", stored as "personality" parameters.

External relay logic has to do ALL the rest, regardless.

Similar multi-personality telco gear, there would be more than one physical path, choice of loop-start or ground start for type of CO trunk, dialing plan optioning for revertive-pulse, DTMF, SF, etc,.. and all on the same PCB of a PBX, PABX, or enhanced "key system" [1].

VFD don't much NEED to have more options on-board than multiple parameter sets, if-even. Some resided on plug-ins before larger NVRAM and configuring / re-configuring over networks got cheap.

[1] By convention, if a "key system" could even DO ground-start or 4-Wire E&M, it was no longer a "Key System" but a CO-equivalent "Private (Automatic) Branch Exchange". But stuff has always tended to blur the edges for marketing purposes... even back in the day of "space division" AKA Analog copper pair dominence.

VoIP voice and data signaling and transport are a whole 'nuther game. much as factory LAN VFD commissioning, maintenance, or even teamed cooperative load sharing have become.

What kind of two speed motor is it? If dahlander then it will be constant torque and lower hp on the lower speed. (think two speed hardinge machines) If this is the case then the stock approach is to hard-wire in high speed configuration and set the VFD up for that.

If, rather, it's a true dual-winding motor (same hp on both speeds), then the idea is to set the VFD up as though it's running two different motors - it is - and store two different parameter sets in the drive.

On edit - apologies as I did not full parse the original post:

"...is there any other benefit to running the low windings at 60hz vs the high windings at 30hz..."

So you answered my question already, it's dahlander wound, and the answer is, no, no benefit running the low windings at 60 vs high windings at 30.

jim rozen said:

What kind of two speed motor is it? If dahlander then it will be constant torque and lower hp on the lower speed. (think two speed hardinge machines) If this is the case then the stock approach is to hard-wire in high speed configuration and set the VFD up for that.

If, rather, it's a true dual-winding motor (same hp on both speeds), then the idea is to set the VFD up as though it's running two different motors - it is - and store two different parameter sets in the drive.

On edit - apologies as I did not full parse the original post:

"...is there any other benefit to running the low windings at 60hz vs the high windings at 30hz..."

So you answered my question already, it's dahlander wound, and the answer is, no, no benefit running the low windings at 60 vs high windings at 30.

Click to expand...

Correct. If a Dahlander motor generates 1 hp on high speed. it will yield 1/2 hp at the same torque on half speed. If the high speed winding gives 1 hp driven by a VFD at 60 cycles, it will give 1/2 hp at 30 cycles from the VFD. The difference is not worth worrying about. Wire the motor for high speed, connect it to a VFD and make chips. People have to flog a simple issue forever.

Bill

9100 said:

Correct. If a Dahlander motor generates 1 hp on high speed. it will yield 1/2 hp at the same torque on half speed. If the high speed winding gives 1 hp driven by a VFD at 60 cycles, it will give 1/2 hp at 30 cycles from the VFD. The difference is not worth worrying about. Wire the motor for high speed, connect it to a VFD and make chips. People have to flog a simple issue forever.

Bill

Click to expand...

Mayhap they "flog it" for a gain they care about and others might not care about?

Would it be too much to ask how it is expected that 2-pole "mode" @ 30 Hz
for half speed would have the same smoothness as four-pole "mode" @ 60 Hz?

Three phases at work, both cases? But still...

Slower speed often does come with a bit more cogging. At 30 Hz, that is not normally an issue.

He can do the switch thing, although unless his VFD can do a "catch on the fly" synch, it may not be a good idea to switch with it "on. Even if it does, there are details.

The smart path here is to switch off VFD drive, change speed, switch on. IF you actually want both native speeds.

As for the frequency, any frequency the VFD will produce is "safe". It heats up somewhat more the higher the frequency, so cooling is important. See manual.

It "should not" make any difference as far as EMI. The switching speed is already so high that the EMI comes from that. But there are more switch events per second at higher frequency, so the net power of EMI may go up somewhat. A filter, or perhaps even just an inductor will generally take care of that if it is an issue.

Mechanically interlocked reversing contactors would be my preference for the switching.

Given you already have the drive and motor, I'd try wiring it up in both configurations and actually testing it. Why deal with theoretical issues if you can actually cut some metal and see if there is a noticeable difference?

The OPs motor is 8/4 pole so the 2 pole concern is irrelevant. I still think there are external connections necessary to jump the leads if both speeds are wanted from the vfd but I'd just deal with the cooling issue and run high with the 4 poles. An external computer fan triggered to start up at 30 hz might be the easiest fix. Dave

SomeoneSomewhere said:

Mechanically interlocked reversing contactors would be my preference for the switching.

Given you already have the drive and motor, I'd try wiring it up in both configurations and actually testing it. Why deal with theoretical issues if you can actually cut some metal and see if there is a noticeable difference?

Click to expand...

Agree that. It's why I sent the VFD's off to recycling, kept only one of two Phase-Perfect, try to NOT use it, upgraded the RPC instead!

Admit to being right lazy about s**t that degrades over time even when settin' idle.

DC drives are 'bout as durable as RPC are.

VFD's are like Athlete's foot or bitchey banket-sharers.

Happy to let some OTHER guy deal wit' either and just run what I got...

beckerkumm said:

......... An external computer fan triggered to start up at 30 hz might be the easiest fix. Dave

Click to expand...

Yep, the VFD should have a relay programmable for a bunch of different possible conditions.

The VFDs I am working with right now have provision for a thermistor in the motor to signal overheating or turn on a fan. It has never been an issue on my machines.

VFDs will definitely cause RFI. When I installed one on my Boston Digital mill, I scrapped the first two mold parts I made because the RFI was altering the signals to the CNC controls. Some .05 mfd capacitors in the encoder circuits cured it.

Bill

Lots of complication and not much is gained from trying to program and run it as a 2 speed motor with a VFD. I have installed VFDs on several 2 speed lathes with 4/2 pole motors, it can be done with a changeover switch with a middle stop position or contactors with interlocks. I have tried this on several 2 speed motor lathes, but often had more issues with motor tuning and unsatisfactory performance ended up with replacing the motors with a single speed. Typically if it is a constant Hp motor I run it on the higher pole setting and boost the top end Hz. Granted most of the 2 speed lathes were Chinese/Taiwanese motors. You can load different acceleration and stopping times depending on the VFD so could switch these if desired at 30 Hz or whatever. A 12kHz carrier frequency is less audible, you need to check the derating of the VFD for carrier frequency. Longevity of the motor, probably you will see no noticeable difference using a higher carrier frequency unless the motor is running continuously. Cooling on most TEFC does not become an issue until below 20 Hz with extended run times. I usually wire in the thermistors in the motors when available, can't recall them ever kicking in. I typically run the lathe motors from 20-75Hz in this type of conversion unless it is a inverter/vector motor with different belting ratios or fewer mechanical speeds.

As previously mentioned you can try both pole settings and see if you notice and difference between 8P 60Hz and 4P 30Hz, but I do am doubtful you will see any appreciable difference.

The feedback from everyone is apricated. This is what I was looking for; that the benefit (if any) of using the 2 native windings rather than running the high windings at 30hz is not worth any extra effort.

I guess I didn’t give enough information on the motor not to cause some confusion, I guess it is Dahlander wound. I didn’t know what that meant, I have just been following the wiring diagram in the manual. Also to clarify, it is wired, running, and making chips since around November. I have ran it on both the high and low windings and I have not seen performance issues on either or when using the high windings set to 30hz; what I do notice is the cogging as JST called it. I currently have everything in “breadboard” configuration and just double-checking final configuration before buttoning it all up properly and hopefully not having any issue with it in the long haul.

Thermite:
I have read about using dv/dt filters working on other VFD installs but have not yet applied any, mostly due to cost. As you pointed out though, they are available used and at reasonable prices so I many look into adding one to the mix. In the past the filters cost more than the drives or motors I was working with so I never bothered.

2 Motor Contactors:
Since there was significant instruction included on how I should initiate the change between the 2 native speeds I thought I would close the loop on how I intended to accomplish this. The drive I am using supports 2 motor function. I currently have E03 set to activate the multistep frequency command to 30Hz. In the 2 motor scenario I set E03 to 12; select motor 2/motor 1 instead of multistep frequency. This allows you to utilize the programmable relay contact outputs set by E27 to drive the switching contactors. No relays outside of the drive itself would be used to initiate the change; an SSR may be needed between the drive and the contactors since the drive contacts are only rated at 0.3A. I was going to use an electrical interlocking arrangement since its what I have; I understand this is not as fail safe as mechanical interlocking contacts. As Phil noted, a power loss scenario needs to be considered, I had not accounted for this and it is a more likely than other “what-ifs”.

Carrier Frequency:
If I understand correctly, the higher carrier frequency increases the heat in the drive, not the motor. So far that has not been an issue, but likely because the default state of the drive is to automatically reduce the carrier frequency to avoid tripping an alarm per the H98 function code.

Thermistor:
I have not yet wired in the thermistor. This drive does support it. This is probably where I should be placing my concerns, not on the speed. One item I am not clear on is if I need to add a 1kOhm resistor to the PTC wiring before connecting to the drive terminal.

Beckerkumm, below is a photo of the motor connections (temporary, need to tidy up still). This is how the bridged connections are being handled. U11 V11 W11 gets you low speed; U12 V12 W12 gets high speed.

Thanks,
Mike

MountaineerMiner said:

The feedback from everyone is apricated. This is what I was looking for; that the benefit (if any) of using the 2 native windings rather than running the high windings at 30hz is not worth any extra effort.

Click to expand...

That may be so in "the general case", but.. you have already MADE 95% OF the "extra effort"? I say stick with it, finish the job, because...

what I do notice is the cogging as JST called it.

Click to expand...

BINGO!!!

A smoother motor translates to finer finishes more easily, and MAY even extend cutting-edge life?

Surely it is never a BAD thing? And.. you've already DONE the hard part of the work?

I have read about using dv/dt filters working on other VFD installs but have not yet applied any, mostly due to cost. As you pointed out though, they are available used and at reasonable prices...

Click to expand...

VERY reasonable, actually. You don't even need but a quarter the mass and impedance I am using.

So, yes. Some among us "Just Will".... go the extra mile for even very modest gains.

Because we can.

Go the extra mile, why? Waste of money and complexity, been there and done that. Yes it can be done, at the end of the day it was a lot more time with no benefit and unnecessary in this scenario. I tried this twice and ended up tearing the 2 motor setting system and reverted to what worked. Look at most factory VFD's in these size lathes, you will find 2 mechanical and a single speed 4 pole motor that typically will be run from 20-120 Hz or higher. I do not see anybody complaining about poor finish quality or a mythical increase in tool life. I have done hundreds of single speed lathe conversions with single speed 4 pole motors and have yet to see any performance or surface finish issues, the same cannot be said for single phase motors. Lets see an insert is $12 to replace, doesn't add to much and you are more likely to replace it because of incorrect speeds and feeds. In a production setting where time and money is at a premium it might be a different story, then again show me the data to support the hypothesis. Unnecessary to add a dv/dt filter in this application, but hey if you must, there are plenty of used ones. If you wanted to use the 2 speed motor than probably should have considered an RPC or Phase Perfect.

mksj said:

If you wanted to use the 2 speed motor than probably should have considered an RPC or Phase Perfect.

Click to expand...

ROFL!

As happens? A massive Square-D transfer switch - one of two, a 3-Phase gen set on its twin - SELECTS between my Phase-Perfect and "dial-an-idler or array of same" RPC!

I'm happy to leave the excuses and rationalizing to you lot who have become "married".... to your shorter-lived mosquito-orchestra and 175 NVRAM setting "Vee Effing Dee's" ... until the end of days! It has kept my Dinosaur Current motors cheaper to source!

Got other, SIMPLER, more durable.. s**t to do in the meantimes...

Lazy, Iyam... VERY-Damn! Penurious as well...

And willing to work HARD.. and spend whatever it takes... to keep it that way..

No. Contradictions do not exist. Check your premises..

Minimum 20-year low/no maintenance thing, mayhap?

Sodding about trying to "program" the most-recent of several VFD in my mid 90's just is NOT in the plan!

Hit the same-old switch. Run whatever TF I still "got".. with nary a care, rather.