[ZeroBacklash]

I have never used a VFD before but I was looking for a single phase input (230V) and three phase output (380 to 415V).
I read on this site that single phase input and three phase output VFD's need to be derated by around 58%, the reasen being that it has to account for increased current load on components at the front end of the VFD.
I don't quite know when that article was written but I have a few questions regarding the VFD.

1. Is this statement true for modern VFD's.
2. Is it better then to go in for a 3phase input VFD's. I was trying to go in for a single phase input VFD because it gave me more flexibility as single phase power easier for me to manage.
3. Is speed ramp up / ramp down a common feature of VFD's or does this have to be accomplished by varying the speed input of the VFD?
4. My current application needs to run the spindle at constant speed, so for that what would be suitable a V/F drive or a vector drive?
5. What points do I have to consider when selecting a VFD?

Thanks in advance!

[Jim Dawson]

I have never used a VFD before but I was looking for a single phase input (230V) and three phase output (380 to 415V).
I read on this site that single phase input and three phase output VFD's need to be derated by around 58%, the reasen being that it has to account for increased current load on components at the front end of the VFD.
I don't quite know when that article was written but I have a few questions regarding the VFD.

You may have a problem finding a 230V to 400V VFD, I'm not aware of any available and was not able to find one with a quick Google search. There are some VFDs available with voltage doublers in them, but normally have 115V input, 230V output. If you must use a 400V motor, you would be better to use a transformer ahead of the VFD. A rotary phase converter/transformer system might be an option to concider of the power requirement of the system justifies it.

1. Is this statement true for modern VFD's.

There are single phase input VFDs that do not require derating. Most of these are < 3.5KW. The rule of thumb that I use is 50% derating for greater than 3.5 KW systems.

2. Is it better then to go in for a 3phase input VFD's. I was trying to go in for a single phase input VFD because it gave me more flexibility as single phase power easier for me to manage.

It depends on the power requirement of your system. If the motor is < 3.5 KW, then single phase is fine.

3. Is speed ramp up / ramp down a common feature of VFD's or does this have to be accomplished by varying the speed input of the VFD?

All VFDs control the Accel/Decel, and can be set to your desired acceleration rates.

4. My current application needs to run the spindle at constant speed, so for that what would be suitable a V/F drive or a vector drive?

A vector drive provides good speed regulation. A vector drive with encoder feedback provides the best speed regulation, but sensorless vector is normally pretty good.

5. What points do I have to consider when selecting a VFD?

Documentation, customer support, voltage input, power output. Again, documentation and support.

[ZeroBacklash]

You may have a problem finding a 230V to 400V VFD, I'm not aware of any available and was not able to find one with a quick Google search. There are some VFDs available with voltage doublers in them, but normally have 115V input, 230V output. If you must use a 400V motor, you would be better to use a transformer ahead of the VFD. A rotary phase converter/transformer system might be an option to concider of the power requirement of the system justifies it.

Currently my motor would be not more than 1.5KW. For voltage I don't know what terminology VFD's use but I was referring to 400V measured line to line in a 3 phase system. Phase to Neutral would still be aronud 220V.
So If I opt for a 3 phase input and 3 phase output VFD, would I still need to derate it? I mean If my motor rating is 1.5KW should I go in for a 2.2KW VFD?

[Goemon]

I run a 7.5hp 3phase 220v spindle from a 1 phase outlet using a 10hp 1ph in / 3ph out VFD. If you buy a cheaper Chinese VFD, 1ph in / 3ph out is available up to 15kw. I struggled to find any non-Chinese premium brand VFD's rated for 1ph in / 3 ph out in larger sizes. I was advised to go up a size for 1ph in / 3ph out Chinese VFDs (which is why I got a 10hp VFD for a 7.5hp spindle).

Almost any 3ph in VFD can be run from a 1ph outlet if you double the size. I.e. A 15hp VFD to run a 7.5hp spindle. The specs on my 1ph in / 3ph out 10hp VFD are almost the same as most 20hp 3ph in VFDs. What you really need to look for is how many amps the VFD needs to draw to output to your spindle. Not all VFDs convert 1ph to 3ph with equal efficiency.

My VFD draws 54a 1ph to output it's max 34a 3ph. This is important to know so you can make sure to install the right size breaker for the outlet. E.g. My spindle draws around 20a 3ph and the VFD draws around 35a 1ph for that, so I installed a 50amp breaker to cover it.

There are Chinese VFDs on eBay that are rated for 1ph 220v in / 3ph 380v out. I haven't seen any 220v in / 400v out but that doesn't mean they don't exist. They certainly aren't common though.

I couldn't find any affordable 220v to 380v or 480v transformers. There were plenty of 480 to 240v or 380v to 240v but any that were rated to step up to 480v (or 380v) were $1500 or more. If you have any budget restrictions I would limit your spindle to no more than 380v and, ideally, you should go for a 220v one. Apparently, you can use a step down transformer in reverse but the math for the required derating gave me a headache.

The most important thing when choosing a VFD is matching it to your spindle specs. In addition to making sure the VFD is large enough to output the required volts and amps, it should also be able to handle the required frequency / speed.

A 4 pole 24,000rpm spindle requires an 800hz VFD. Most VFDs max out at 400hz which means you would be limited to 12,000rpm with a 4 pole 24k spindle. This info should be on the spindle's nameplate.

That's what I found when shopping for my VFD. It's not that complicated once you get passed the jargon. Just look at what the spindle needs, buy the right size VFD and make sure you install the right size breaker to power it.

[Jim Dawson]

Currently my motor would be not more than 1.5KW. For voltage I don't know what terminology VFD's use but I was referring to 400V measured line to line in a 3 phase system. Phase to Neutral would still be aronud 220V.
So If I opt for a 3 phase input and 3 phase output VFD, would I still need to derate it? I mean If my motor rating is 1.5KW should I go in for a 2.2KW VFD?

Normally there are 2 classes of VFDs, 200V class and 400V class (before I get flamed here, yes I know there are higher voltages available). The 200V class encompasses 200 to 240 Volt, and the 400V class encompasses 380 to 415 volt. This includes both single and 3 phase inputs.

Given that your requirement is 1.5 KW, you have many options. As Goemon stated, there are apparently VFDs that are 200V single phase in, 400V, 3 phase out, so that pretty much solves your problem with voltage conversion.

No derating required if the VFD is rated for single phase input.

[mactec54]

Currently my motor would be not more than 1.5KW. For voltage I don't know what terminology VFD's use but I was referring to 400V measured line to line in a 3 phase system. Phase to Neutral would still be aronud 220V.
So If I opt for a 3 phase input and 3 phase output VFD, would I still need to derate it? I mean If my motor rating is 1.5KW should I go in for a 2.2KW VFD?

So a question do you have a 3Phase Power supply or a single Phase Power supply, you are talking about both so what do you have

[ZeroBacklash]

So a question do you have a 3Phase Power supply or a single Phase Power supply, you are talking about both so what do you have

I do have 3 phase power coming in but its 3 individual phases each with its own energy meter, and Ive routed each phase to seperate sections to balance the load. So I would prefer 1ph in / 3 ph out VFD, but if I can't escape it I could use a 3ph in / 3ph out VFD.

[ZeroBacklash]

Normally there are 2 classes of VFDs, 200V class and 400V class (before I get flamed here, yes I know there are higher voltages available). The 200V class encompasses 200 to 240 Volt, and the 400V class encompasses 380 to 415 volt. This includes both single and 3 phase inputs.

Given that your requirement is 1.5 KW, you have many options. As Goemon stated, there are apparently VFDs that are 200V single phase in, 400V, 3 phase out, so that pretty much solves your problem with voltage conversion.

No derating required if the VFD is rated for single phase input.

So I'm a still confused. That article I linked to in the first post said that derating is required for a 1ph in / 3 ph out VFD. So my questions are
1. Is derating required for 1ph in / 3ph out VFD?
2. Is derating required for 3ph in / 3ph out VFD?
3. Can a 3ph in / 3ph out VFD, run with single phase input. (Goemon said this was possible but with 100% derating)
4. What are the pros and cons of 1ph in vs 3ph in VFD but both with 3ph out VFD?

[ZeroBacklash]

I run a 7.5hp 3phase 220v spindle from a 1 phase outlet using a 10hp 1ph in / 3ph out VFD. If you buy a cheaper Chinese VFD, 1ph in / 3ph out is available up to 15kw. I struggled to find any non-Chinese premium brand VFD's rated for 1ph in / 3 ph out in larger sizes. I was advised to go up a size for 1ph in / 3ph out Chinese VFDs (which is why I got a 10hp VFD for a 7.5hp spindle).

Almost any 3ph in VFD can be run from a 1ph outlet if you double the size. I.e. A 15hp VFD to run a 7.5hp spindle. The specs on my 1ph in / 3ph out 10hp VFD are almost the same as most 20hp 3ph in VFDs. What you really need to look for is how many amps the VFD needs to draw to output to your spindle. Not all VFDs convert 1ph to 3ph with equal efficiency.

My VFD draws 54a 1ph to output it's max 34a 3ph. This is important to know so you can make sure to install the right size breaker for the outlet. E.g. My spindle draws around 20a 3ph and the VFD draws around 35a 1ph for that, so I installed a 50amp breaker to cover it.

There are Chinese VFDs on eBay that are rated for 1ph 220v in / 3ph 380v out. I haven't seen any 220v in / 400v out but that doesn't mean they don't exist. They certainly aren't common though.

I couldn't find any affordable 220v to 380v or 480v transformers. There were plenty of 480 to 240v or 380v to 240v but any that were rated to step up to 480v (or 380v) were $1500 or more. If you have any budget restrictions I would limit your spindle to no more than 380v and, ideally, you should go for a 220v one. Apparently, you can use a step down transformer in reverse but the math for the required derating gave me a headache.

The most important thing when choosing a VFD is matching it to your spindle specs. In addition to making sure the VFD is large enough to output the required volts and amps, it should also be able to handle the required frequency / speed.

A 4 pole 24,000rpm spindle requires an 800hz VFD. Most VFDs max out at 400hz which means you would be limited to 12,000rpm with a 4 pole 24k spindle. This info should be on the spindle's nameplate.

That's what I found when shopping for my VFD. It's not that complicated once you get passed the jargon. Just look at what the spindle needs, buy the right size VFD and make sure you install the right size breaker to power it.

Thanks for sharing your experiences Goemon.
What brand of Chinese VFD's are you referring to is it Huanyang?

For my application I want to run the final output at around 60 to 100rpm, basically its an unwinder application so I want to maintain constant velocity of the process. But the rpm of the motor would need to change to maintain the process velocity of certain m/s. As the spool starts getting empty the motor would need to speed up to keep the process velocity.

[Jim Dawson]

So I'm a still confused. That article I linked to in the first post said that derating is required for a 1ph in / 3 ph out VFD. So my questions are

1. Is derating required for 1ph in / 3ph out VFD?

No, they are designed for single phase input.

2. Is derating required for 3ph in / 3ph out VFD?

No, as long as it's running on 3 phase input and properly sized for the motor.

3. Can a 3ph in / 3ph out VFD, run with single phase input. (Goemon said this was possible but with 100% derating)

Many 3 phase input VFDs can be run on single phase input. I normally derate 50% unless I expect the motor to run at or near 100% load for extend periods, then I would derate 75 to 100% depending on the application. For the most part, in most machine tool type applications it is unusual to need 100% motor power for extended periods.

4. What are the pros and cons of 1ph in vs 3ph in VFD but both with 3ph out VFD?

The single phase in VFD simplifies installation where 3 phase is not readily available. But, at full rated motor power, the current draw on the single phase line Is about 170% of the current draw if it had a 3 phase input.

[ZeroBacklash]

No, they are designed for single phase input.


No, as long as it's running on 3 phase input and properly sized for the motor.


Many 3 phase input VFDs can be run on single phase input. I normally derate 50% unless I expect the motor to run at or near 100% load for extend periods, then I would derate 75 to 100% depending on the application. For the most part, in most machine tool type applications it is unusual to need 100% motor power for extended periods.



The single phase in VFD simplifies installation where 3 phase is not readily available. But, at full rated motor power, the current draw on the single phase line Is about 170% of the current draw if it had a 3 phase input.

Many thanks for the extended reply Jim, that nails it.
One doubt that I had is an ac motor is optimised to run at a particular frequency right ? Typically 50 / 60 Hz. So a VFD tends to vary the frequency from 0 to 400Hz, which is out of the range of the AC motors operating frequency, while trying to maintain constant torque, but with reduced power.
1. So is this torque that the VFD tries to maintain constant is the rated torque? I mean the (Rated Power / Rated RPM)
2. Will the motor heat more towards the lower frequency regions 0 to 40hz or the higher frequency regions 70 to 400Hz. At 400 the rpm of the motor would be 24000 rpm which is out of bounds of a AC motor 4 pole rated at 1500rpm speed? So how does this work out can regular motors be run at such insane speeds or are those meant only for the high speed spindle motors?

[Jim Dawson]

Many thanks for the extended reply Jim, that nails it.
One doubt that I had is an ac motor is optimised to run at a particular frequency right ? Typically 50 / 60 Hz.

That is true for the older motors, modern vector duty motors are normally rated for a wide range of speeds. Even with the older motors you are normally safe running between 30 and 90 Hz.

So a VFD tends to vary the frequency from 0 to 400Hz, which is out of the range of the AC motors operating frequency, while trying to maintain constant torque, but with reduced power.

You would want to limit the upper (and perhaps lower) frequency settings of the VFD, the frequency range is set when setting up the VFD. For instance, I think I have the VFD on my mill set for 1 to 140 HZ, even though the VFD is capable of 400Hz output. If I tried to run the mill motor at 400Hz (12,000 RPM) it would probably explode, the motor is rated at absolute maximum of 6000 RPM.

1. So is this torque that the VFD tries to maintain constant is the rated torque? I mean the (Rated Power / Rated RPM)

When powered by a sensorless vector or other vector drive, most motors will develop full torque at near zero RPM. So they operate in constant torque mode up to the motor nameplate RPM, then switch over to constant power above that. So that means the torque falls off as the RPM increases above the nameplate RPM.

2. Will the motor heat more towards the lower frequency regions 0 to 40hz or the higher frequency regions 70 to 400Hz. At 400 the rpm of the motor would be 24000 rpm which is out of bounds of a AC motor 4 pole rated at 1500rpm speed? So how does this work out can regular motors be run at such insane speeds or are those meant only for the high speed spindle motors?

When running at low speeds and high torque, heating can become a problem and may require an external fan on motors not rated for that duty. Most of the smaller 3 standard phase motors <3.5KW can be safely run at 3600 RPM, even those with a nameplate rating of 1400 RPM, many modern vector duty motors are rated at 4500 to 6000 RPM maximum. Spindle motors are a special case and are designed to run at very high RPMs.

[ZeroBacklash]

That is true for the older motors, modern vector duty motors are normally rated for a wide range of speeds. Even with the older motors you are normally safe running between 30 and 90 Hz.



You would want to limit the upper (and perhaps lower) frequency settings of the VFD, the frequency range is set when setting up the VFD. For instance, I think I have the VFD on my mill set for 1 to 140 HZ, even though the VFD is capable of 400Hz output. If I tried to run the mill motor at 400Hz (12,000 RPM) it would probably explode, the motor is rated at absolute maximum of 6000 RPM.



When powered by a sensorless vector or other vector drive, most motors will develop full torque at near zero RPM. So they operate in constant torque mode up to the motor nameplate RPM, then switch over to constant power above that. So that means the torque falls off as the RPM increases above the nameplate RPM.



When running at low speeds and high torque, heating can become a problem and may require an external fan on motors not rated for that duty. Most of the smaller 3 standard phase motors <3.5KW can be safely run at 3600 RPM, even those with a nameplate rating of 1400 RPM, many modern vector duty motors are rated at 4500 to 6000 RPM maximum. Spindle motors are a special case and are designed to run at very high RPMs.

Thanks again for the explanation!!
So are these so called "vector duty motors" special motors meant for working with "Sensored Vector Drives"? Are all modern motors vector duty? From what I saw off this form Baldor / WEG seem to be manf vector duty motors?

[Jim Dawson]

Thanks again for the explanation!!
So are these so called "vector duty motors" special motors meant for working with "Sensored Vector Drives"? Are all modern motors vector duty? From what I saw off this form Baldor / WEG seem to be manf vector duty motors?

Yes, vector duty motors are designed to operate with vector drives. Not all modern motors are vector duty rated, but the standard duty motors from the major manufactures will work just fine in light to medium duty applications, like my mill. For a maximum performance application I would use a vector duty rated motor, for instance, my lathe spindle motor.

EDIT:

To expand a bit on motor operating conditions:

Mill spindle; Constant rpm when cutting, 30 to 60 % load, normally operated in the 30 to 120 Hz range, acceleration/deceleration set to 3 seconds. Standard 3 phase (Baldor), 4 pole, 1800 base RPM, 3 HP (2.2KW), standard motor shaft fan for cooling, not vector rated but running on a sensorless vector VFD, single phase input, manual speed control.

Lathe Spindle; RPM varies with part diameter (constant surface speed), rapid RPM changes, acceleration/deceleration set in the VFD to 0.1 second (actual accel/decel is controlled in software), dynamic braking, 30 to 120% load, normally operated in the 0 to 200 Hz range. Purpose built spindle motor (Fanuc), 6000 nameplate RPM, 4 pole, 10 HP (7.5KW), external fan cooled, vector duty rated, encoder feedback, 3 phase input VFD.

[CitizenOfDreams]

Documentation, customer support, voltage input, power output. Again, documentation and support.

1. Price. If a brand name VFD does not fit your budget, it simply does not matter how well the documentation is written of how pleasant is the hold music when you dial the 1-800 number.

[Goemon]

Thanks for sharing your experiences Goemon.
What brand of Chinese VFD's are you referring to is it Huanyang?

For my application I want to run the final output at around 60 to 100rpm, basically its an unwinder application so I want to maintain constant velocity of the process. But the rpm of the motor would need to change to maintain the process velocity of certain m/s. As the spool starts getting empty the motor would need to speed up to keep the process velocity.

Huanyang is one Chinese brand but there are others. E.g.:

https://www.ebay.com/itm/11KW-15HP-3...sid=m570.l1313

The advantage of Huanyang VFDs over other Chinese brands is that they are widely used by members here, so when you have questions (and you most certainly will), there will be people who can answer them.

[mactec54]

Thanks again for the explanation!!
So are these so called "vector duty motors" special motors meant for working with "Sensored Vector Drives"? Are all modern motors vector duty? From what I saw off this form Baldor / WEG seem to be manf vector duty motors?

Are all modern 3Ph motors Inverter Duty ( Vector Duty ) No they are not, most are just a regular 3Ph Ac motor

The Inverter Duty motor is the same as a Vector Duty motor in terms of the motor part, the only difference it the Vector Duty has an Encoder, and does not come in sometimes a motor frame size you may want,both will work with a Sensorless Vector Drive, you can add an Encoder to a Inverter Duty motor, and take the full benefit of the Vector Drive, so in the end you can end up with a cheaper package than if you where to buy a Vector Duty Motor

The wash down Inverter Duty motor from Baldor is a good example of this, almost all major AC Motor manufacturers build Inverter Duty Motors

[Goemon]

That is true for the older motors, modern vector duty motors are normally rated for a wide range of speeds. Even with the older motors you are normally safe running between 30 and 90 Hz.



You would want to limit the upper (and perhaps lower) frequency settings of the VFD, the frequency range is set when setting up the VFD. For instance, I think I have the VFD on my mill set for 1 to 140 HZ, even though the VFD is capable of 400Hz output. If I tried to run the mill motor at 400Hz (12,000 RPM) it would probably explode, the motor is rated at absolute maximum of 6000 RPM.



When powered by a sensorless vector or other vector drive, most motors will develop full torque at near zero RPM. So they operate in constant torque mode up to the motor nameplate RPM, then switch over to constant power above that. So that means the torque falls off as the RPM increases above the nameplate RPM.



When running at low speeds and high torque, heating can become a problem and may require an external fan on motors not rated for that duty. Most of the smaller 3 standard phase motors <3.5KW can be safely run at 3600 RPM, even those with a nameplate rating of 1400 RPM, many modern vector duty motors are rated at 4500 to 6000 RPM maximum. Spindle motors are a special case and are designed to run at very high RPMs.

My VFD has two settings. One is for constant torque motors like you find on CNC router spindles and a second setting for constant power set-ups (like a milling head with gearing). No matter what VFD you get, you have to set it up correctly for the motor it will run. This is relatively easy if you understand your motors specs. It's easy to make a mistake if you don't though. For example, this guy:

Setting up a Huanyang VFD for a CNC router spindle — The Half-Baked Maker

He felt so confident in his expertise that he published instructions for others but.... he doesn't understand the difference between 2 pole and 4 pole motors. He says "my spindle is 2.2kw so I set it to 4 pole" which is nonsense. This is why someone who tried to follow his "advice" is asking (in the comments below) why he can't get his 24000rpm spindle to go above 12,000 rpm....

If you understand the motor specs, setting up the VFD is relatively easy once you have a list of parameters to set. It's like doing a multiple choice exam with a list of answers.

On cooling, My understanding is that extra is required if you plan to use a motor at more than 25% less than it's base speed. I don't really know if this is right but I do know that improper cooling can be a major performance limitation.

Most air cooled spindle motors have a fan on the shaft so cooling is proportional to spindle speed which is why they don't do well at low speed. I paid double the price to get an electric fan cooled spindle so I could use it at any speed. These have a seperate 24v input just for the cooling fan. Others use water or compressed air cooling which is even more effective. If you plan on using your motor at well below it's base speed (without using gearing) it is worth asking a few extra questions on the cooling thing.

On derating (or not) for a 1 phase in / 3ph out VFD, while it is technically not required, I was advised to go up a size with Chinese VFDs as you can't rely 100% on their published specs.

[mactec54]

I do have 3 phase power coming in but its 3 individual phases each with its own energy meter, and Ive routed each phase to seperate sections to balance the load. So I would prefer 1ph in / 3 ph out VFD, but if I can't escape it I could use a 3ph in / 3ph out VFD.

So you have 3Ph power supply, then you should be using it for this install, this makes it simple for you to just have a regular 3Ph VFD Drive and Spindle Motor that matches your voltage, you then can split it up into Single Phase, in your cabinet for the other things that need Single Phase supply, this is how it should be done, don't worry to much about the balance thing, what important is the supply and wiring is of the right amperage to do the job

[ZeroBacklash]

Are all modern 3Ph motors Inverter Duty ( Vector Duty ) No they are not, most are just a regular 3Ph Ac motor

The Inverter Duty motor is the same as a Vector Duty motor in terms of the motor part, the only difference it the Vector Duty has an Encoder, and does not come in sometimes a motor frame size you may want,both will work with a Sensorless Vector Drive, you can add an Encoder to a Inverter Duty motor, and take the full benefit of the Vector Drive, so in the end you can end up with a cheaper package than if you where to buy a Vector Duty Motor

The wash down Inverter Duty motor from Baldor is a good example of this, almost all major AC Motor manufacturers build Inverter Duty Motors

So If I get you right is an inverter duty motor same as vector duty motor?
Does vector duty motor have better insulation and better cooling and an encoder attached. I mean apart from these 3 differences is there anything more to a vector duty motor?
Can a standard 3ph ac motor + encoder be used like a vector duty motor in combination with a sensored vector drive?