Mitsubishi AC Servo Spindle Retrofit

[joeavaerage]

Hi,
looks like the Mitsubishi MR-J2S series of servo drives have digital and analogue inputs, ie Step/Dir and/or voltage Speed and Torque modes.

This is a 3.5kW MR-J2S drive:

https://www.ebay.com/itm/23387699900...MAAOSw85hgFCeC

The question is....'does it suit your servo?'

Craig

[jlmccuan]

OK. I've decided to ditch the Mitsubishi motor and drive. Now what? Where can I get a comparable or step up in performance, say 8-10000 rpm and 5 to 8 HP with a drive to run it under Mach3? This is a belt drive setup with a BT40 tool changer.

[joeavaerage]

Hi,

OK. I've decided to ditch the Mitsubishi motor and drive

That is a shame, Mitsubishi is good quality, it will not be cheap or easy to replace it. May I assume that you did not find any Mitsubishi drives with regular
Step/Dir inputs that would match your motor?.

There are a number of small servos, say 1kW or less that will attain 5000rpm, and yet others that might do 8000rpm, but are less powerful than you require.
You might try researching Baldor, they seem to have a range of servo motors that have high rpm ratings, and great quality, but not cheap!

Most AC servos in the 5kW to 7.5kW class are 3000 rpm or less, 2000rpm is common as is 1500rpm. I suspect that there may be few, if any servos of the power output
you want and capable of the rpm you want.

Another reality is that a reasonable practical maximum with domestic single phase 230VAC wiring is 2.2kW. If you have , or specifically install larger wiring and circuit protection,
you might get closer to 4kW, but in that category all the servo and VFD manufacturers are expecting their device to have three phase input. That you are talking 5 to 8 hp
can I assume that you have three phase electricity on site?

So while AC servos have many things to recommend themselves to spindle service, compact for the power output, continuously rated with generous overload
characteristics and so on, such few that are likely to meet you requirements are likely hugely expensive also.

For the power and speed you want I would be thinking about asynchronous spindle motors.

Ordinary three phase induction motors (2 pole) run at 3600rpm (synchronous) in the US (60Hz), and you might get lucky and run the same motor up to 7200rpm
with a VFD. Might want to replace the bearings first though! They are not especially compact but are readily available. They are not rated or intended for inverter service but
most quality manufactured motor will survive use with a VFD.

Perske is a company that make a wide range of inverter ready induction motors, many capable of high rpms.

JIanken is a Chinese company they have developed a good reputation for quality and performance at fair prices. In particular they do a range of high speed induction motors
for belt drive spindles:

https://www.jian-ken.com/high-speed-...dle-power.html

They have a 4.2kW (5.6hp) 18000 rpm unit requiring 380VAC (nominal) three phase at up to 300Hz.
They also have a 5.5kW (7.3hp) 15000 rpm unit again with 380VAC three phase at up to 250Hz.

Craig

[jlmccuan]

Thanks. Craig. I have 240VAC 3 phase for the spindle motor and Z axis motor. I thought about running a VFD rated motor as I can use a pin for tool change orientation and have wondered about their low speed torque. I checked out the link, but all I found were spindle motor combinations. I need a motor to belt drive my spindle. Maybe they'll have a 240 VAC 3ph version or a transformer I could go to 380 with.

[joeavaerage]

Hi,

I checked out the link, but all I found were spindle motor combinations. I need a motor to belt drive my spindle.

Jianken do a series of high speed motors that are intended for belt driving a spindle, the link I posted was to the model page.
You could run a nominal 380VAC motor with 230VAC but you would lose the top end speed.

It seems that most high speed asynchronous motors do not like running at very low speeds, they tend to overheat. You will see a speed/torque diagram in the PDF drawing
of the motor that you are interested in.

Jianken are responsive to email, assuming they are not locked down of course.

Craig

[dazp1976]

Hi,



Jianken do a series of high speed motors that are intended for belt driving a spindle, the link I posted was to the model page.
You could run a nominal 380VAC motor with 230VAC but you would lose the top end speed.

It seems that most high speed asynchronous motors do not like running at very low speeds, they tend to overheat. You will see a speed/torque diagram in the PDF drawing
of the motor that you are interested in.

Jianken are responsive to email, assuming they are not locked down of course.

Craig

I though we were talking about a motor for a mill to spin the atc bt40 spindle that's fitted to the machine already via belt drive?.
Those are high speed ones for routers?.

[joeavaerage]

Hi,

Where can I get a comparable or step up in performance, say 8-10000 rpm and 5 to 8 HP with a drive to run it under Mach3?

That's what OP asked for, and these Jianken motors are the closest I know of, certainly at the cheaper end of the market. Try Perske and see how much they cost!

Craig

[jlmccuan]

I finally got tired of wondering and hooked up a VFD to the power leads to the AC Servo motor. It runs and the VFD changes the speeds. I haven't put a load on it to see if it has torque. Any guesses or things to watch for. I have the cooling fan running.

[mactec54]

I finally got tired of wondering and hooked up a VFD to the power leads to the AC Servo motor. It runs and the VFD changes the speeds. I haven't put a load on it to see if it has torque. Any guesses or things to watch for. I have the cooling fan running.

It most likely is not a servo motor then, if it is running with a VFD Drive, just an AC synchronous motor with an encoder, You can check to see if it is a servo motor by touching (2) of the motor power wires together, ( Power Disconnected) if there is a resistance to turn the motor shaft you can then count how many poles the motor has, as it will bump at each pole, just rotate the motor shaft (1) rotation to count the number of poles, if there is no change when you put the (2) wires together it is not a AC servo motor

[joeavaerage]

Hi,
I tried the same thing with a servo some years ago.

Like you I got motion and thought that it would be sufficient as a spindle motor. The problem is that as the load comes on a servo drive would force more current through the
servo and thus increase the torque to match the load. An ordinary V/F curve VFD won't do that. I tried a vector drive VFD also, and it was better but still not up to much, the
torque authority was just not there, and that is the key advantage of a servo type motor.

Craig

[dazp1976]

I finally got tired of wondering and hooked up a VFD to the power leads to the AC Servo motor. It runs and the VFD changes the speeds. I haven't put a load on it to see if it has torque. Any guesses or things to watch for. I have the cooling fan running.

.

[jlmccuan]

I assumed it was an AC Servo because the drive is an AC Servo Drive. Maybe I got lucky and it will run. Now what type of VFD would you recommend to get the torque control and hopefully the ability to jog to a position pin for tool changes? Who makes a well documented and supported drive with good tech support?

[mactec54]

I assumed it was an AC Servo because the drive is an AC Servo Drive. Maybe I got lucky and it will run. Now what type of VFD would you recommend to get the torque control and hopefully the ability to jog to a position pin for tool changes? Who makes a well documented and supported drive with good tech support?

There are no VFD Drives that are suitable for Servo Motor Drives, for spindle orientation you need to use the encoder feed back to the drive to position the spindle, there are a lot of VFD Drives that will do this part Yaskawa being the best drive, (Is Expensive) but won't solve the problem if your motor is a Servo, Check your motor like I said by connecting any (2) Phases together, this will tell you straight away if it is a Servo or a regular 3Ph Motor

[mactec54]

jlmccuan

A VFD Drive that can give you PM control may help; this will never give you correct torque and running of the motor though.

The main difference between a VFD and a Servo drive is how the motor is controlled an AC 3ph motor uses Voltage to Frequency, a Servo uses Frequency to Voltage and requires Encoder feedback to keep the rotor in position

[joeavaerage]

Hi,

I assumed it was an AC Servo because the drive is an AC Servo Drive. Maybe I got lucky and it will run. Now what type of VFD would you recommend to get the torque control and hopefully the ability to jog to a position pin for tool changes? Who makes a well documented and supported drive with good tech support?

I suspect it IS a servo, which has a permanently magnetized armature surrounded by a three phase winding. Matecs test will confirm that within seconds.
If it is the there is NO VFD that will give you satisfactory torque control. The best VFDs are vector controlled, and vector control relies on the drive being able to determine
the rotor position (magnetically) by an 'estimator' which uses the current caused by the slip of an induction motor. With a synchronous motor there is no, or should not be, any
slip. Ergo the 'estimator' fails, and the vector drive becomes no more than a complicated V/F drive.

There are a couple of superb videos by Texas Instruments on 'Field Oriented Control' which will expand on Matecs description very well. There is yet more videos in the series
explaining the 'estimator' control strategy, also called vector control. It has its uses, but synchronous motors are not it.

You may be familiar with BLDC motors, they commonly have Hall sensors rather than an encoder to detect rotor position, and are used to 'commutate' the stator windings.
Such a device would work better with your motor, assuming you retrofitted Hall sensors in the correct arrangement, than a VFD. The resultant torque is lumpy though, but you
would get torque control.

I would recommend you watch the video, or even more than one, then you'll be much better prepared to make an informed decision regarding whether a VFD will work well
enough for your purpose.

I experimented with several VFDs and a largish (3kW) servo some years ago and was very underwhelmed. The video tells me why.

Craig

[mactec54]

Hi,



I suspect it IS a servo, which has a permanently magnetized armature surrounded by a three phase winding. Matecs test will confirm that within seconds.
If it is the there is NO VFD that will give you satisfactory torque control. The best VFDs are vector controlled, and vector control relies on the drive being able to determine
the rotor position (magnetically) by an 'estimator' which uses the current caused by the slip of an induction motor. With a synchronous motor there is no, or should not be, any
slip. Ergo the 'estimator' fails, and the vector drive becomes no more than a complicated V/F drive.

There are a couple of superb videos by Texas Instruments on 'Field Oriented Control' which will expand on Matecs description very well. There is yet more videos in the series
explaining the 'estimator' control strategy, also called vector control. It has its uses, but synchronous motors are not it.



You may be familiar with BLDC motors, they commonly have Hall sensors rather than an encoder to detect rotor position, and are used to 'commutate' the stator windings.
Such a device would work better with your motor, assuming you retrofitted Hall sensors in the correct arrangement, than a VFD. The resultant torque is lumpy though, but you
would get torque control.

I would recommend you watch the video, or even more than one, then you'll be much better prepared to make an informed decision regarding whether a VFD will work well
enough for your purpose.

I experimented with several VFDs and a largish (3kW) servo some years ago and was very underwhelmed. The video tells me why.

Craig

There are some VFD Drives which can do PM motors which may help a little over a Vector control VFD Drive, I still have never seen one drive a AC Servo Motor, like a matching Servo Drive can though.

[joeavaerage]

Hi,

There are some VFD Drives which can do PM motors which may help a little over a Vector control VFD Drive,

I've never seen or heard tell of one, mind you thats not saying much.

I still have never seen one drive a AC Servo Motor, like a matching Servo Drive can though.

That I can well believe.

As a consequence of failing to drive my otherwise perfect servo as a spindle motor with any of the VFDs I tried I elected to build my own Field Oriented Control servo drive, but that is
a whole new project all in itself! Even more recently I found a second hand Allen Bradley 1.8kW servo and drive and have been using that instead, and has rather put my home brew servo drive on the
backburner.

Craig

[mactec54]

Hi,



I've never seen or heard tell of one, mind you thats not saying much.



That I can well believe.

As a consequence of failing to drive my otherwise perfect servo as a spindle motor with any of the VFDs I tried I elected to build my own Field Oriented Control servo drive, but that is
a whole new project all in itself! Even more recently I found a second hand Allen Bradley 1.8kW servo and drive and have been using that instead, and has rather put my home brew servo drive on the
backburner.

Craig

Most of the major VFD Drive manufacturers have the PM motor control built into their VFD Drives, Yaskawa I believe was the first, but all the others have had this for a few years, including Mitsubishi VFD Drives

The PM motor can be controlled by open loop or closed loop with the VFD Drive having Encoder feedback, which any quality VFD Drive has this option

Here is an article on how to set up a VFD Drive for PM motor, there are some that know and some that pretend to know

https://www.controleng.com/articles/...or-with-a-vfd/

[jlmccuan]

Thought I'd include a followup conclusion for this thread for others with similar problems.

After weighing my options and realizing there was virtually no market interest in an untested unidentified motor, I figured I'd take my chances and hook up an old VFD I had lying around. Six wires later, I hit run, and the motor spun up to what later was found to be 8200 rpm. After playing with the speeds for a while and making sure the spindle would run at 9000 without overheating, I ordered a new VFD from Automation Direct, ACNND-2010. 3 days later it landed and after a quick call to tech support about some parameters, my spindle is merrily spinning up to just at 10,000rpm with a spin-up and spin-down of 5 seconds each way after hooking up the braking resistor banks. Now for the load testing and tuning.

Thanks to all those who gave input.

[mactec54]

Thought I'd include a followup conclusion for this thread for others with similar problems.

After weighing my options and realizing there was virtually no market interest in an untested unidentified motor, I figured I'd take my chances and hook up an old VFD I had lying around. Six wires later, I hit run, and the motor spun up to what later was found to be 8200 rpm. After playing with the speeds for a while and making sure the spindle would run at 9000 without overheating, I ordered a new VFD from Automation Direct, ACNND-2010. 3 days later it landed and after a quick call to tech support about some parameters, my spindle is merrily spinning up to just at 10,000rpm with a spin-up and spin-down of 5 seconds each way after hooking up the braking resistor banks. Now for the load testing and tuning.

Thanks to all those who gave input.

So, it was just a regular AC 3Ph spindle motor like what Yaskawa and many others use, what is your max frequency, you are using to get the 10,000 RPM this tell you the Pole count.