Motor Control Course Questions.

tim_callinan · Oct 12, 2021

I'm an instructor of mechatronics at a 2 year community college. I really appreciate the advice I've received from this group over the years. We're starting a electric motor control course - this is be our students first introduction to motors and controlling them. We've been told by our industry advisory board to definitely pay attention to VFDs and three phase motors - this is no problem for us.
One of our adjuncts and a lot of our graduates are working for Amazon or amazon subcontractors. I've been getting a little feedback saying a lot of their equipment is starting to be powered by DC motors and servos which is news to me. Obviously 24v is safer. Ive also been sniffing around the internet and found these lads. Check about 4 mins into the video. I thought it was pretty impressive.
https://www.youtube.com/watch?v=_SYhCRwacDs&t=484s
My plan was to spend most of the time on AC motor controls but how deep into DC motors should I be getting. Any imput/feedback is defo appreciated.
Tim

rupej · Oct 12, 2021

I've mostly been seeing DC motors on low power conveyors. I could see why Amazon would use them. But in general, most everything else I deal with is 3-phase.

Peter Nachtwey · Oct 12, 2021

It would be best to ask specific questions because I could write a book.
DC motors are simple to control.
AC motors are usually used on applications with higher mass or inertia. They present more of a challenge.
I can't imagine a 2 year college getting that deep.
I have NEVER had a class on motors, yet I can model and auto tune them and control them with precision. They aren't that difficult. For a 2 year college I would place more emphasis on getting hands on.

I would place more emphasis on sizing and wiring. If this is done correctly the rest is easy.

GaryS · Oct 13, 2021

the link it just to sell you their motor
there are in fact many motors that meat that type of operation
most motors in use today are 3 Phase motors along with other consideations cheep to build and have a long life
yes the insulation class is an important consideration for the system designer to consider but most technictions will have to learn to work with what's there.
there are still some DC motors out there on older systems but they are beaing phsed out
small roller conveyors use 24 VDC motor built into the rolls
but iy you want to do systems then you really should learn VFD's what ever brand is in use where you work.
the 3 Phase motor is the simplest motor to work with just 3 power connections the speed it controlled by the frequency of the power feeding then
generally in the US 60HZ 1800 rpm base paeed for a 4 pole motor in the EU 50HZ 1500 rpm for the same motor I have setup motors to run on a VFD from 1 HZ or less to over 300 HZ, your in control just select your hardware carefully

Jim3846 · Oct 13, 2021

Amazon uses alot of 24vdc motorized roller. (its not the huge DC motors of yesterday)
24vdc MDR (motorized drive roller) 2 biggest manufacturers are
Itoh Denki - different companies use different controll mod
Insight Automation

AC motors - 4 types
Overloads, fusing, and breakers, what is proper?
VFD controlled (open loop, closed loop, braking resistors, multiple motors to one vfd, )
Accross the line starters control
Soft starts control
servo control

Emergency stop of above devices and requirements

Different types of network communications as it relates to above
Ethernet - everyone does this with a green site
Asi
Profibus
Past networks that fell out of favor
ControlNet
DeviceNet
Canbus

24vdc MDR is usually done as a field network controlling in field.

Gene Bond · Oct 13, 2021

The design shown in the video is a great packaging job for *some* applications. They are correct in the facts of a compact package and higher performance than steppers, VFD/Induction motors and open loop DC motors/drives. However, the advantage of an integrated drive/controller in the motor goes out the door in harsh environments.

There is no performance advantage to having the drive/controller electronics integrated in the motor. The biggest disadvantages are the connector integrity and heatsink exposure with less than ideal environments. Imagine an application where oil, water, dust, etc. can get caked on the motor. With a 'normal' servo motor, they are IP65 or 66, and can be washed down when they get dirty. The connectors shown are not waterproof. The higher rated connectors cost more, and if they were available on this design would make them more suitable in these tough industrial applications.

I've never been a real proponent of the integrated drive/motor design, due to replacement cost when they fail. Maybe it's an advantage in today's world, with the level of maintenance talent that is available. But, what needs to be done to transfer the programming? Is there an add-on instruction for the major PLC's, to automatically recognize the replacement unit and download the programing? This is getting more and more standard for the industry leaders.

I admit, I am interested in the product. However, it's not revolutionary, rather it's derivative. This concept has been available in steppers for a decade or so. Servo drives with motion control included have been around for a good while as well.

There is a case to be made for simplifying the number of components in a system, but care must be taken to consider the end user's troubleshooting and replacement concerns. Most times the initial cost is just a fraction of the overall cost of ownership.

Gene Bond · Oct 13, 2021

BTW, I spend a good bit of my time explaining the workings of Induction motors. Most Engineers, Technicians, etc. have little knowledge of the reason an AC motor acts and reacts to a load and a drive. In 90% of the applications, they don't have to. However, as soon as they get an odd application, and have some troubles with trips and errors, they are lost.

Unfortunately, there's no easy alternative to working your way out of a problem when you get in over your head. A good coach on the other end of the phone sometimes is the best teacher. Troubleshooting skills are #1, and the only way I know how to learn is experience.

My suggestion would be to assign a project to set up a drive & motor to do something, and then behind their back, break it with a simple, common change, like a parameter change in the drive, or a loose wire (or terminal crimped on insulation), etc. THEN have them dig themselves out...

alfhuckett · Oct 24, 2021

GaryS said:
...generally in the US 60HZ 1800 rpm base paeed for a 4 pole motor in the EU 50HZ 1500 rpm for the same motor I have setup motors to run on a VFD from 1 HZ or less to over 300 HZ, your in control just select your hardware carefully

How long before the motors burnt out running at 1Hz? The cooling fan is on the end of the motor and you would have no cooling at that speed.

rupej · Oct 24, 2021

alfhuckett said:
How long before the motors burnt out running at 1Hz? The cooling fan is on the end of the motor and you would have no cooling at that speed.

Some motors are rated for full load at or near 0hz. Other times, the load is so low at low speeds it is a non-issue. Or there is an external fan. Lots of reasons why this could be totally fine.

busarider29 · Oct 24, 2021

Gene Bond said:
The design shown in the video is a great packaging job for *some* applications. They are correct in the facts of a compact package and higher performance than steppers, VFD/Induction motors and open loop DC motors/drives. However, the advantage of an integrated drive/controller in the motor goes out the door in harsh environments.

There is no performance advantage to having the drive/controller electronics integrated in the motor. The biggest disadvantages are the connector integrity and heatsink exposure with less than ideal environments. Imagine an application where oil, water, dust, etc. can get caked on the motor. With a 'normal' servo motor, they are IP65 or 66, and can be washed down when they get dirty. The connectors shown are not waterproof. The higher rated connectors cost more, and if they were available on this design would make them more suitable in these tough industrial applications.

I've never been a real proponent of the integrated drive/motor design, due to replacement cost when they fail. Maybe it's an advantage in today's world, with the level of maintenance talent that is available. But, what needs to be done to transfer the programming? Is there an add-on instruction for the major PLC's, to automatically recognize the replacement unit and download the programing? This is getting more and more standard for the industry leaders.

I admit, I am interested in the product. However, it's not revolutionary, rather it's derivative. This concept has been available in steppers for a decade or so. Servo drives with motion control included have been around for a good while as well.

There is a case to be made for simplifying the number of components in a system, but care must be taken to consider the end user's troubleshooting and replacement concerns. Most times the initial cost is just a fraction of the overall cost of ownership.

Maxon IDX series BLDC motors are IP65 rated. Drive/positioning control integrated. Fully custom configurable. Reasonable and comparable cost to conventional segregated Motor/Drive/controller systems in the same class.

VAN · Oct 25, 2021

I didn't see anyone mention softstarts, but maybe types of motors and different ways to start them.

For instance we had some little 400hp blowers that we had to start with delays and current limit. So soft start first blower throttle current for a minute and then it was usually mostly up to speed (this saves you on the electric bill) and then start the next blower.

Also, the power company will get upset if you sap a bunch of current, something something grid and you blew up something. (I didn't do it and wasn't apart of the electrical design, I just get to hear about it.)

NetNathan · Oct 25, 2021

It is advisable to check with motor mfg to find out lowest (minimum rpm) and highest (maximum rpm, yes you can overspeed most motors) speed to run.

ZestyMozzarella · Oct 25, 2021

In my experience, I have witnessed some old DC motors on belt lines for plating but beyond that and low end conveyor system, almost everything I run into has been AC motors and VFDs. As these old DC motors have been dying, we have been converting them to AC motors and VFDs. That said, I reside in manufacturing of metals and fabrication, cannot speak for Amazon but given their belt systems, low end 24VDC motors to power their belts to lessen exposure to 120VAC would not surprise me and is likely advisable on their ends.

GaryS · Oct 26, 2021

To answer you question about burned out motor I can't remember ever losing a motor and you will not if you install them correctly.
i have a milling machine with the table running a fector drive at .75 hz output to the motor
the operator liked to run that slow on the last pass to polish the work.
I have done many crane projects where my standard on a hoist at a stop command ramp the motor speed down to 0 HZ and suppend the load on the vfd and motor only at that 0 HZ for about 15 sec. before setting the brake. Never had a motor problem and 0 wear on the brake pads. A client actually did a test over 5 years and could not measure any brake ware
It's all in the setup if you are losing motors then something is not setup correctly
and you would be suprised how many time I have run into this on on jobs.

Motor Control Course Questions.

tim_callinan

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rupej

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Peter Nachtwey

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GaryS

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Jim3846

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Gene Bond

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Gene Bond

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alfhuckett

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rupej

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busarider29

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VAN

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NetNathan

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ZestyMozzarella

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GaryS

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