Inverter, Atex motors, star, delta

[Joe9]

Dear Friends,

I need technical solution for my problem;

Specification:
I have two motors, type:

1. HCT/ATEX 45-2T-2 (R/MIN=2800), (400V-3,60A), (KW-1,50)
2. HCT/ATEX 45-2T-3 (R/MIN=2860), (400V-5,00A), (KW-2,20)

Also, every motor has its own inverter:
Inverters are from INVERTEK DRIVES (Optidrive).

My project is to provide thoose two motors working in first (lower speed) all the time , and sometimes they need to work in second speed (higher - maximal possible).
Those speeds must be provided by changing frequency with inverter.

My questions are:
1. How to know which maximal frequency (Hz) are motors made for? - ( I think maximal frequency would be the higher speed)or they can work on any frequency?
2. Also how to make electrical diagram correctly ( If I have inverters; do I use only delta connection or I can use only star connection. Or I need to use star for start and delta for running?
3. Can somebody help me to design electrical diagram?

I hope you can understand my problem, also I will be very happy if somebody can solve my problem, I am affraid of making false wiring diagram.

With kind regards,

Joe
9

 

[BrianPetersen]

R/MIN = 2800 for the first one, and 2860 rpm for the second one, is it not? Given the voltage and the RPM, I am going to ASSume that these are 50 Hz motors since normal 3-phase in Europe is 400 volts and if it's in Europe, that means 50 Hz, and secondly, 2800 / 2860 rpm is a normal amount of induction-motor slip below the 3000 rpm synchronous speed for a 50 Hz two-pole motor.

I don't think it's normal practice to exceed the nominal rated frequency (50 Hz). Perhaps it can be done, but it's not normal practice.

The best answer for how to connect the motor is to read the manual for the VFD and do what it says. A motor that is connected to a (good) VFD normally doesn't require switching between connection types, because the VFD can provide an appropriate frequency ramp-up on starting, so that the motor does not start with a jolt as it would if it were directly switched into the mains.

 

[Joe9]

Thank you on your answer...

It means I can connect motor as delta?

For first speed I use lower frequency and for max speed I use 50Hz?

What is usual practice in those situations?

Kind regards

 

[jraef]

You connect the motor as the motor nameplate says that you connect the motor for the voltage rating it has. USUALLY, if you are using 400V, that will be a Star connection on a dual voltage (400/230) motor; star is always the higher voltage, delta is always the lower voltage. But that is not 100% guaranteed to be the case, the only way to know is to know the specific details of the motor in question.

The purpose of a variable frequency drive is to vary the speed of the motor. So if you only want two speeds from it, that's fine.

To be bluntly honest though, the nature of your questions brings up a concern as to whether or not you are qualified to be doing this. ATEX motors are for use in areas where explosive gasses are present, and any mistake can have extremely disastrous consequences, even deadly. The fact that you are unaware of how motors are connected or how VFDs work indicates that you are very likely also unaware of the myriad of other details that must go into a safe and successful installation design. I implore you to surrender this project to someone with more relevant experience. Watch and learn from them, ask plenty of questions, but please to not accept the meager assistance you can get from on-line resources as a substitute for proper engineering practices.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[Joe9]

I have been never working with vfd s.

So i have questions...

I need to find out min and max rated speed of motors after that i need to calculate which speeds i need for my needs and thats all.

If star is higher (400V) I connect it like star only.

This should be simple like this.
Any other comments?

 

[Joe9]

Dont worry I will not do what you say without checking it with qval. Person... Here i am to find direction for solution

 

[waross]

If the motor is rated for 400 Volts with a star connection, it may be possible to run up to about 4800 RPM with a delta connection. But, as jraef says, there are a few details that should be addressed by an on-site expert to set this up. The V/Hz ratio with a 400 Volt star connection is 8 V/Hz. With a delta connection the V/Hz ratio will be 4.62 V/Hz. The current on the 2.2 kW motor will go from 5 Amps to 8.66 Amps. The power at 4800 RPM will be about 3.8 kW.
Some of the things that VFDs can do in the hands of an expert are amazing.
Now if the motors are rated for 400/690 Volts you must use a delta connection for 400 Volts and you will lose torque if you exceed rated speed at rated voltage.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[zlatkodo]

Highest speed (frequency) is dependent on the rotor diameter.

[URL unfurl="true"]http://winding.wix.com/design[/url]

 

[Joe9]

OK,

I get you technical charactertistics of fans,
also maximamal airflow (m3/h) for every fan is:

MAX1. 10650 m3/h
MAX2. 12750 m3/h

I realised that with fvd I will use only one type of connection or star or delta.

If I want provide those two maximal airflows, which type of connection should I use? (What frequeny would it be?)
If I want half (m3/h)/2 I change only frequency; nothing else?

Summary which type of connection and what frequency would it be for lower speed, what frequency would it be for higher speed?

Do you need any additional informations to provide me an answer?

Kind Reagrds

 

[Skogsgurra]

Sorry Joe, you do not seem to be able to ask the right questions. And you do not understand the answers, even if they are perfectly valid an relevant.

Your last posting doesn't mea anything. The airflow as such can't be used to make any engineering decision except regarding ducts and such things. It doesn't influence the motor connection at all.

Do us and yourself a favour and hire a competent electrician. If you go on like this, you will, as Jeff says, cause an accident.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[Joe9]

Forum is here to ask stupid questions and answering on them correctly or incorrectly.

There is no reason for arguing...
Who know is it my school project maybe?

Does anyone from here can answer me on question? If there is no enough informations please ask me... Do not think on ex zone vents are ex but not in the ex zone.

I need simple answers... Frequency range for my needs, and connection star or delta.

And comments if you have positive please.

Kind regards

 

[BrianPetersen]

All of the questions that you have asked (with the exception of the air-flow amounts) can be answered if you open the technical manuals and specification sheets for the specific VFD and motor that you have. No one here is going to do that for you. That is YOUR work to do.

It is not normal practice to exceed the motor's nominal operating speed and therefore frequency, and that is 50 Hz. Obviously that should be matched to the higher of the two airflow requirements. The lower one will be obviously at a lower frequency - probably somewhere near 42 Hz if one makes the reasonable assumption that the delivery volume is in proportion to the motor and fan speed.

For making the electrical connections, I really think you need to read the technical manuals for the equipment that you are using. It is ALL in there.

 

[waross]

Possibly the best and safest solution will be to forget the VFDs.
Use the proper drive ratio (belts and pulleys) to develop the maximum speed of the fan. Then use a damper and appropriate actuator to reduce the air delivery to the lower level.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Joe9]

Brian thank you.

I understand now the range of frequency better.

Is it practice to connect 2kw motors in delta over vfd?

It has to be simple. Problem is technical documentation which is very bad. There is hard to find answers... You can search on sodeca web page and you will find nothing useful.

Is it ok to run those motors in delta what do you think is there chance for overheating?

 

[Joe9]

Warros

I have to use vfd.

Kr

 

[BrianPetersen]

Let me put it this way.

If the motor has the capability of being connected in either star or delta then the nameplate on that motor or the documentation that comes with it should state what the voltage, current, etc ratings are for each connection method. Whatever the connection method is that matches up to the 400 V supply, is the connection method that you have to use. It doesn't matter for this purpose that the power is going through a VFD.

If there is no nameplate on the motor that states this and no documentation, then either (1) contact the motor manufacturer and obtain the required information directly from them (and get a new nameplate!), or (2) if this cannot be done, scrap the motor and buy a new one with known ratings and connect it the way the instructions say it is supposed to be done. The consequences of having a major equipment failure or starting a fire because of the motor being connected incorrectly are far greater than the cost of a new motor.

As for the VFD, a trivial Google search reveals the manufacturer's website. With a little bit of investigation I was able to find the user guide. I don't know which model you have, so I won't mislead you by giving a link to the random one that I found. In that documentation, it has a section (on page 23, of the Optidrive model that I randomly chose) that discusses exactly what you are asking about.

Read it!

 

[Joe9]

Ok, I got all documentation maybe not in best languages.

See link for vfd

http://invertek.com.au/ODE-2-24150-3KA4X.html?sc=2&category=16748

See attachments for motor 2/2

 

[Joe9]

motor picture 1/2

 

[Joe9]

This is first time I am dealing with something what is not instrumentation.

Maybe my questions are iritating, but it is way of learning...

 

[ozmosis]

Joe9
If this application is an actual real requirement, you should note to following:
Using the Invertek drive on an ATEX EEx e designated motor is not permitted unless you independently test and certify the combination of drive and motor, or Invertek do this for you. You will invalidate any certification the motor has, the moment you connect and run with the VFD. You need to use a VFD that is certified for this specific combination of motor, under ATEX requirements.
I suggest discuss with the motor manufacturer. It is in their interest, as well as yours.
It is good to be learning, but not with an explosion.