cheap method VSD for small 380 volt motor 1

[FredEvans]

Hello all,
I own a small factory manufacturing engineering components and need to wire up a .55 kw 380 volt electric motor to run off 220 volts.
I am not a "sparky" but i will get my sparky to do the wiring up.
my question is how is the cheapest method to do the job.
I want 380 volt because the motor will be switched on and off continually and I believe that that 380 volt can
handle continous on/off operation.
your advice is appreciated
regards fred evans

 

[itsmoked]

A VFD will not step up to that voltage.

While a VFD can help with frequent on/off cycling it won't help with the 380V. You should be using a 230V motor NOT a 380V motor.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jraef]

Notwithstanding Keith's statement, there ARE a couple of off-brand VFDs that will "boost" a 220V supply to 380V if you need to get to 380V for an existing motor but only have 220V available. These are going to be more expensive and more prone to failure than a straight voltage rating because of the added components necessary to do this (and the fact that the people selling them take standard drives from other mfrs and modify them).

But the question is still, WHY? What is it that you perceive to be the value in using a motor not designed for the voltage that you have? As Keith said, if you have 220V available, just use a 220V rated motor. Going to a 380V rated motor does not increase the reliability.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[waross]

Very often 220 Volt motors and 380 Volt motors are identical, as in the same motor.
The difference between 220 Volts and 380 Volts is a delta connection versus a star connection for the three windings.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[FredEvans]

I think the gist of the replies is why i want to go to 380
my experience with 220 volt motors may be at fault.
( I should perhaps rather have asked about changing from single phase to 3 phase ??)
my single phase 220 volt motors are usually started by a condensor. in continued on and off
usage the motor has in the past burnt out.
On changing the motors to 3 phase the problem was solved.
however the wiring of 3 phase to the point of usage within the factory requires quite a lot of cost while
there is already 220 volt supply. so I thought that it might be easier to change the 220 to 3phase and it might be cheaper
your suggestions are appreciated
regards

fred

 

[RedSnake]

If the start stopp of the motor by the condenser burns the motor out, how often does the motor then start/stops, in which intervalls?
Motors have different ratings for heating and duty, S1 to S8 meaning that if a motor is to start and stopp often in a short wile, it needs to be able to withstand the heat or it needs to be cooled down between the starts and stops not to overheat.
So maybe a 220 VAC motor with another duty rate would help.
Does your motor include a fan?
A fan on the motor may also help.

I am not familiar with the function of a condenser so I am not sure how important it is that it starts and stops at the correct time if the intervalls are to tight.
A on-delay timer might work if there isn't any other consequences if the motor isn't allowed to start when the condenser says so.
When the signal from the condenser says off (goes zero) the timer starts preventing a new start until the time has run out giving the motor time to cool down before it start again.

Still thinks getting a motor that can handle the duty is the best choice.

For S1-S8 duty diagram look in

https://www.eng-tips.com/viewthread.cfm?qid=485148

Best Regards A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[LionelHutz]

Yes, the single phase motor is more failure prone, it has the capacitor and often a centrifugal switch. But, you don't need to switch to 380V to get a 3-phase motor. Many VFD's can do single phase in and 3-phase out but then you add the VFD to the failure possibilities. Overall, I suspect a decent quality single phase motor would be more reliable than a VFD. But, if you need a LOT of starting and stopping or speed control then the VFD makes sense.

 

[FredEvans]

Lionel- you hit the nail on the head- yes I do have a lot of starting and stopping like maybe
start- run 20 seconds - stop 5 sec - run 20 secs - again and again so the .
(I dont want to put in a clutch) .
so for this duty - what about a start and stop switch with a contactor?
thanks for the advice
regards

fred

 

[RedSnake]

Whit that duty cycle I do understand that the motors does not last very long first you have a start current and some seconds of running which generates heat especially the start current and then only 5 seconds of cooling time.

Maybe a soft starter would help it will reduce the start current it might be enough to not overheat the motor.
Whit that duty cycle you would need a motor for S4 maybe even S5 to do the job.

https://docs.rs-online.com/1e91/A700000007746358.pdf

Best Regards A



“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein