Motor Config

[DM7.ENG]

Hi there
I am used to seeing dual voltage motors stating delta 400V Star 690V and my understanding of this is The line voltage in delta is the same as the phase voltage as it would be for any other parallel circuit and there is only ever 1 winding at a given instance between 2 phases. With star the phase voltage is VL/root 3 I.e. 230V between u1,v1,w1 and midpoint so... Would I be right in saying that in star config there is never actually 690V present anywhere in the circuit and it is still only 400? and all we are doing is increasing the impedance by a factor of 3 to that of delta and so the 690 is simple 400/root3 x3 and so the 690v reference is simply stating what these windings are rated for and not what u will get if u connect the motor this way!?

Also I Came across a dual voltage induction motor the other day with name plate info that was pretty unfamiliar to me, The name plate stated Delta 230V Star 400V

Does this mean that we would need to apply approx 130v to get 230V delta because if I applied a normal 230V and measure between 2 phases Id get 400V?

Think I must be looking at things wrongs can anyone advise.
thanks

 

[Lucien Nunes]

For many years we have been standardised on 230V L-N, 400V L-L supplies (or similar, 240/415 etc) for general industrial applications. Most motors are intended to run in delta on 400V L-L, i.e. each winding sees 400V. This enables star-delta starting where the 400V windings see only 230V during the start to reduce starting current and torque. Such a motor will of course run at full power in star on a 690V L-L supply if you have one.

Recently there has been a trend towards 690V L-L supplies for heavier industry, as modern switchgear and control gear can be made to suit at moderate cost and there is a considerable saving in copper. Traditional 400V motors can be used by wiring them in star, but 690/1190V motors will run in delta. The only thing you can't do is power 230V single-phase loads but in heavy industry they would be on separate distribution anyway. With the advent of inverter drives, we're also less interested in star-delta starting than in the past.

There were machines designed for 230V L-L, in fact I have a generator that puts out 20kVA at 230V corner-grounded delta, would be 133V L-N as you mention if there were a neutral, which there isn't. Shipboard power is often 230V delta, where single-phase 230V loads run L-L, this was also used in the past for European domestic supplies. That is why to this day the German / West European Schuko plug was not polarised, because it was expected that both pins would be lines. We're just not very familiar with this in general UK practice.

 

[DM7.ENG]

Thanks for that. So in short if I come across a 230vdelta 400v star motor and I want to run it in delta I would have to supply it from a source which is 3 phase approx 130v phase to neutral

For many years we have been standardised on 230V L-N, 400V L-L supplies (or similar, 240/415 etc) for general industrial applications. Most motors are intended to run in delta on 400V L-L, i.e. each winding sees 400V. This enables star-delta starting where the 400V windings see only 230V during the start to reduce starting current and torque. Such a motor will of course run at full power in star on a 690V L-L supply if you have one.

Recently there has been a trend towards 690V L-L supplies for heavier industry, as modern switchgear and control gear can be made to suit at moderate cost and there is a considerable saving in copper. Traditional 400V motors can be used by wiring them in star, but 690/1190V motors will run in delta. The only thing you can't do is power 230V single-phase loads but in heavy industry they would be on separate distribution anyway. With the advent of inverter drives, we're also less interested in star-delta starting than in the past.

There were machines designed for 230V L-L, in fact I have a generator that puts out 20kVA at 230V corner-grounded delta, would be 133V L-N as you mention if there were a neutral, which there isn't. Shipboard power is often 230V delta, where single-phase 230V loads run L-L, this was also used in the past for European domestic supplies. That is why to this day the German / West European Schuko plug was not polarised, because it was expected that both pins would be lines. We're just not very familiar with this in general UK practice.

 

[telectrix]

Thanks for that. So in short if I come across a 230vdelta 400v star motor and I want to run it in delta I would have to supply it from a source which is 3 phase approx 130v phase to neutral

yes. those motors are meant to run star on 400V L-L.or delta on 230V L-L.

 

[Darkwood]

I use the 400/230 all the time and there popularity has rocketed since the increased usage of 1ph to 3ph drives which generally have 1ph 230 L/N input and 3ph 230v output, having 400/230 motors fitted to new machinery is common in the smaller motor rangers where they may be initially connected in star to 3ph 400v DOL starting and leaves the option for fitting a VSD at a later date if required without the need to replace all the motor kit, only to alter the config of the motor from star to delta. I'm in textile industries a lot and when I build a panel the customer may request certain attributes of control like web retention of the fibre where several motors all need to speed up and slow down in unison in say a carding line making quilts - the large cylinder motor is usually Star/Delta starting 690/400 and all the slave motors are VFD controlled looking at a common closed loop speed signal from the big motor. Where a carding machine doesn't require to maintain a controlled web and just needs to provide fibre for filling pillows say then some of the motors don't need VFD control and can simply be DOL and I usually leave room to convert if they change the usage of the carding section of the machine.

So for me I find common use for both 690/400 and 400/230 motors in my line of work. 40yrs-60yrs ago these machines were speed controlled using expensive manual/gear speed controls and all motors will have been 690/415 or even DC run of drive cards to achieve the same result - mostly expensive to repair and maintain due to their obvious age and the inability of the mass influx of cheap labour in this industry to look after and maintain the machinery.

 

[DM7.ENG]

Sorry just to clarify on this also, The 690v characteristic, Am I right in saying that does not apply to a 400V line to line system, The way I am looking at it is if I measure between 2 phases regardless if the motor is star or delta I get 400 as expected therefore, at no point in the system is there 690v

yes. those motors are meant to run star on 400V L-L.or delta on 230V L-L.

 

[Darkwood]

These motors are commonly used for Star/Delta starting over here where our 3ph is 400v but some large industries and other countries do have 690v available for direct connection, yes your correct on a standard power supply you will not see more than 400v line to line (or 415 give or take in reality).

 

[Rampage]

I use the 400/230 all the time and there popularity has rocketed since the increased usage of 1ph to 3ph drives which generally have 1ph 230 L/N input and 3ph 230v output, having 400/230 motors fitted to new machinery is common in the smaller motor rangers where they may be initially connected in star to 3ph 400v DOL starting and leaves the option for fitting a VSD at a later date if required without the need to replace all the motor kit, only to alter the config of the motor from star to delta. I'm in textile industries a lot and when I build a panel the customer may request certain attributes of control like web retention of the fibre where several motors all need to speed up and slow down in unison in say a carding line making quilts - the large cylinder motor is usually Star/Delta starting 690/400 and all the slave motors are VFD controlled looking at a common closed loop speed signal from the big motor. Where a carding machine doesn't require to maintain a controlled web and just needs to provide fibre for filling pillows say then some of the motors don't need VFD control and can simply be DOL and I usually leave room to convert if they change the usage of the carding section of the machine.

So for me I find common use for both 690/400 and 400/230 motors in my line of work. 40yrs-60yrs ago these machines were speed controlled using expensive manual/gear speed controls and all motors will have been 690/415 or even DC run of drive cards to achieve the same result - mostly expensive to repair and maintain due to their obvious age and the inability of the mass influx of cheap labour in this industry to look after and maintain the machinery.

Those 1PH - 3PH VFD's are a godsend for running industrial machines on a single phase supply!

In your Carding Line example, is it the VFD or the motor that's providing the speed signal to control the VFD for the other motors?

 

[Darkwood]

Those 1PH - 3PH VFD's are a godsend for running industrial machines on a single phase supply!

In your Carding Line example, is it the VFD or the motor that's providing the speed signal to control the VFD for the other motors?

Depends what we are doing, if we are wiring from scratch or rigging a old one up to get it going on a temp basis... on carding machines you usually have a speed sensor on the main cylinder so the main star/delta motor gets to speed before the other motors come into play this can be done with a timer but isn't fail safe, at a key point you fit an encoder to give a closed loop feed back and then the motor speeds are all slaved off it... there are a few less reliable methods that are a quick fix like a proxy sensor through a signal converter to give an analogue signal the drives can read and interpret - the pain in these set ups is ensuring all the drives have the correct scaling values for each motor to maintain the web doesn't bunch or stretch when starting and stopping... an art in itself.

Look up open loop and closed loop speed control for a better understanding, its better closed loop so the drives respond to actual data been directly fed back from a rotating shaft.

 

[netblindpaul]

DW,
Have you ever worked with/on virtual lineshaft systems via SERCOS?

 

[Darkwood]

DW,
Have you ever worked with/on virtual lineshaft systems via SERCOS?

Im aware of the systems but due to the abuse and poor maintnance these machines tend to have I don't use it as its easier to do a quick repair to a copper cable and minimise downtime than to source and get a replacement fibre optic cable and the interfaces etc ... My local RS does SERCOS but still have to order it in and wait - not a viable option for some of my customers.

 

[netblindpaul]

I used to work for the company that "invented" SERCOS!
SERCOS III is over copper, "CAT5" "type" but Cu never the less, it was SERCOS II that was fibreoptic.
I never worked with SERCOS I, I suspect it never made it to market.
However SERCOS has much greater uses than simulated line shafting.

 

[Darkwood]

I used to work for the company that "invented" SERCOS!
SERCOS III is over copper, "CAT5" "type" but Cu never the less, it was SERCOS II that was fibreoptic.
I never worked with SERCOS I, I suspect it never made it to market.
However SERCOS has much greater uses than simulated line shafting.

Maybe have another look into it then, it was the fibre optic side that put me off for the above reasons - excellent for other applications I dare say but wasn't for me.. cheers