Inverter problems why oh why

[cliffed]

After several asks,been told that an inverter speed controller cannot be used on a 3 phase 2 speed,4 pole motor.
All the tech guys,installers etc,couldn't tell me this at the beginning of job,but when testing the motor,it just didn't sound right,2 motors later one call I've made as finally gotten to the cause.
All the specification,was adhered to,so frustrating,what's happening out there.

 

[LeeH]

I'm having difficulty deciphering your post to be honest.

Did you have a problem with a non vsd rated motor on a vsd?

And what's a 2 speed motor?

 

[Andy-1960]

If you changed the motor why didn't you change it for a normal 4 pole motor?
I am interested in what they said and why it won't work, can you tell me more?

 

[Darkwood]

After several asks,been told that an inverter speed controller cannot be used on a 3 phase 2 speed,4 pole motor.
All the tech guys,installers etc,couldn't tell me this at the beginning of job,but when testing the motor,it just didn't sound right,2 motors later one call I've made as finally gotten to the cause.
All the specification,was adhered to,so frustrating,what's happening out there.

It's hard to make out where in this work you actually sit, are you just the end installer working to a spec and design passed down from above or are you responsible for the diagnosis, design and upgrade from concept to completion?..
If the former then indeed you are copping for the mistakes of others but if you are taking this on yourself then it is down to you to be fully knowledged in the different motor types and their suitability for VSD, manufacturers etc sell there products on the presumption you are fully aware of there suitability and limitations for any given job.
I assume been a 2 speed motor it may well be dual Kw rated and suits to different requirements of the machine, swapping out for a standard motor may not be suitable to the needs of the machine but info' is limited here.

 

[Darkwood]

I'm having difficulty deciphering your post to be honest.

Did you have a problem with a non vsd rated motor on a vsd?

And what's a 2 speed motor?

A 2 speed motor as obvious as it may sound is a motor that can run at 2 different speeds depending on which you choose through the controls, it has a wiring arrangement that allows you to choose between 2 set speeds and can in some cases look like a standard star/delta connection which for those who are dabbling in this side of the industry can have disasterous results if mistaken for the wrong kind.
You can commonly find 2 speed motors on lathes but your probably more familiar with them on cranes where you have slow and fast options for travel and/or hoist operations.

 

[LeeH]

Thank you, never come across one in my industry.

How does that work seeing as the number of poles dictate the revolutions? Seems a expensive and complicated winding arrangement.

 

[Darkwood]

Thank you, never come across one in my industry.

How does that work seeing as the number of poles dictate the revolutions? Seems a expensive and complicated winding arrangement.

I'm going to let you ponder that one for a little while but if you get stuck just click the link and read up on the Fig2 section halfway down the page .. it actually is cost effective to have a motor with 2 speeds options as oppose to all the mechanical gearing required to achieve the same thing, motors can be wound and arrange for almost any use and variation you can imagine, they are not limited to the arrangements of a standard fixed speed cage motor.
Connecting Motors for a Change Of Voltage - http://www.industrial-electronics.com/AC-DC-motors/15_Connecting-Motors-Change-Voltage.html

 

[cliffed]

I'm having difficulty deciphering your post to be honest.

Did you have a problem with a non vsd rated motor on a vsd?

And what's a 2 speed motor?

It's a bit complicated,the company I work for quoted for connecting all equipment on site,without much co operation off others.
There were several motors to connect,but the client insisted on this particular motor to have 2 speed control.
All communication with tech,motor suppliers were done by our company,I was told this & that,& now problems have arisen,with this motor being controlled by a inverter supplying variable speed control.
It's a 400 v,connected in star,& isnot compatiable with this inverter.

 

[cliffed]

If you changed the motor why didn't you change it for a normal 4 pole motor?
I am interested in what they said and why it won't work, can you tell me more?

I've not changed the motor,another company's done that,it's a 400 v motor,2 speed 4 pole motor,it's connected in star,& apparently not suited to an inverter

 

[cliffed]

A 2 speed motor as obvious as it may sound is a motor that can run at 2 different speeds depending on which you choose through the controls, it has a wiring arrangement that allows you to choose between 2 set speeds and can in some cases look like a standard star/delta connection which for those who are dabbling in this side of the industry can have disasterous results if mistaken for the wrong kind.
You can commonly find 2 speed motors on lathes but your probably more familiar with them on cranes where you have slow and fast options for travel and/or hoist operations.

Correct,2 different speeds,but some idiot advised a inverter to control this motor

 

[Darkwood]

@cliffed How many wires at the connections and how many terminals are there?

 

[cliffed]

@cliffed How many wires at the connections and how many terminals are there?

Ok there are 6 connections,L1 L2 L3,& either star or delta links.
This mother rated at 400 volts,so connected in star,links horizontal.

 

[westward10]

How do you know it is a two speed motor.

 

[cliffed]

How do you know it is a two speed motor.

It's got a high & low connection,also in its name place it's got 2/4 figure. Meaning 2 speed 4 pole.

 

[westward10]

So as it is now it is connected high speed, what is low speed no link across any of the terminals.

 

[cliffed]

Yes connection on high speed,links in star formation

 

[westward10]

Does the rating plate clearly show the different speeds and the same or different horse powers.

 

[cliffed]

Yea different rpms,amperage ,min 1.14,max 2.41 amps

 

[cliffed]

All this came to light a couple of days ago,it's just been a lack of information & communication between parties.
The guy I phoned,summed it up really,why would you put a Vsd inverter on that kind of motor,when it already is a 2 speed motor.

 

[westward10]

Stab in the dark, I suspect you have a Dahlander wound motor which is two speed and as it is connected with the link across three terminals it for high speed, this is actually star/star connected. I haven't dabbled with this for years and Darkwood can probably say whether this is correct and whether it will run from an inverter speed controller.

 

[cliffed]

Yea sounds right,I've been told it won't work with inverter,& it certainly don't sound right when controlled by inverter.

 

[westward10]

Have you tried running it DOL without the inverter because theoretically it should run like any other induction motor.

 

[cliffed]

Thought about doing that,but bit worried,just can't connect cables without some protection on motor,not got another starter to try that yet,but an option

 

[westward10]

Yes you need to control it through a starter or a switch fuse. I think you need to do this to confirm the motor is okay. Maybe when Darkwood comes back on he can throw some light.

 

[cliffed]

Thanks will do that when I'm back on job,it definetly wants sorting ,there's been so many involved,& nothing seems to happen.

 

[westward10]

Who put the link across the three terminals.

 

[cliffed]

I did,being either star or delta connection

 

[westward10]

Ah I have been thinking about this and assumed the link was already there so my Dahlander theory could be incorrect. What you "could" have is a double wound motor which is essentially two motors in one, a high speed and a low speed. One set of terminals for high speed the other for low. Ditch the link and just connect to one set of terminals, if it is definitely a two speed motor it may function now high speed on one set of terminals reconnect to the others for low.

 

[cliffed]

Yea,not tried that yet,will see thanks.

 

[sunray]

Is there any drawing or other info about links on the motor?
There are too many ways of making a motor run and different speeds to guess.

 

[cliffed]

Basically on the lid it is either star or delta symbols,the motor is 400 v only,my take on it originally a conventional starter was going to be used,high,low speeds,stop & start.
Bringing 6 cables back to that position,but others above me had the idea about using a Vsd inverter.

 

[cliffed]

Here's the lid

 

[westward10]

This isn't a two speed motor in the sense of the word it is a standard motor where low speed is star and high speed is delta. You need to connect the motor as you had it DOL and see what happens without the inverter in circuit.

 

[cliffed]

Ok thanks

 

[LeeH]

We need a picture of the data plate, this is just guess work.

That box lid suggests it's a normal/standard/whatever asynchronous induction motor.

Smaller ones are 230/400, larger ones 400/600.

Have you connected a 230/400 motor in delta via the drive? They do get somewhat hot like this unless it's a single phase drive.

Pics of the plate, drive, and motor wired up are required to solve this riddle.

 

[cliffed]

Here's the nameplate,the motor connected in star,as shown on pic,controlled by Vsd.

 

[LeeH]

I'm glad you started this thread, its been a learning curve for me RE 2 speed motors and the 2 types. A - Dahlander (2 speed 1 winding) and B - 2 speed 2 winding.

For VSD control you can connect it to the high speed winding.

Read this, I am not the author.

You need to know how it is being used and what type of 2 speed motor it is. 2 speed motors are either 2 speed 2 winding (2S2W) or 2 speed 1 winding (2S1W) type, you need to determine that first. (A "Dahlander" motor as described above is what we call a 2S1W motor in this country).

For 2S2W, the low speed can be any other normal motor speed that is available via the number of poles, because they are two completely separate windings inside of the case. So the high speed can be 2 poles (3600RPM) and the low can be 6 poles (1200RPM) or 4 poles (1800RPM) synchronous speeds.

2S1W motors are different in how they are configured and are going to be either Constant Torque, Variable Torque, or Constant HP depending on the wiring configuration. The quick way to tell is to look at the nameplate: If the Low Speed HP is 1/4th of the High Speed HP, it's Variable Torque and if the HP is 1/2 of the High speed, it's Constant Torque. If you use a VFD on either of these types, you just leave it connected in High speed and the VFD will provide constant torque at any speed. So you actually have MORE torque available at low speed if you has a VT configuration before.

If the HP is the same at both speeds, or the nameplate only provides one HP, it is Constant HP (CHP). That's where it's going to take some decision making based on what the machine does. You see CHP in a lot of metal working machine tools because some operations might require MORE torque at lower speeds as cutting tools "bite" deeper into the material. A classic case in point is a drill press where at slow speed, the bit is requiring more torque to keep it cutting as the bit digs deeper per rotation than at high speed where it takes lots more, but smaller, bites. In this kind of application, you may need to keep the 2 speed connection in play and program the VFD for the two separate loads. In that case, you buy the VFD for the highers Amp draw from the motor nameplate, then you have to have interlocking to make sure you can't change speeds without shutting the VFD off first. 2S2W motors can be like this too, so you need to know exactly what you are working with and what the machine does.

 

[cliffed]

Thank you,trying to get my head around this one,very interesting,ongoing saga.

 

[westward10]

Glad it has helped you Lee I haven't dabbled in motor theory for years although much of that was dc. I think this is a standard wound squirrel cage induction motor where if you keep the same voltage the star connection is low speed and delta is high speed but I think this needs conforming with the inverter drive out of the equation or as the yanks would say Wye and Mesh.