FLC of 1~ motor 0.3kW, 220V, FLA 2.2A

[Pham Van Hung]

Dear sirs,

A single phase AC motor (fan) 0.3 kW (0.4 HP), 220V 50Hz, with nameplate FLA 2.2A.
I would appreciate anyone to tell me what is exact FLC of the motor?
I interpolated from NEC table 430.248 that the FLC is 4.4A. Is it correct?

Kind regards,
HungPV

 

[winnie]

The NEC tables for motor current are only vaguely related to the actual current drawn by the motor when running. These tables are essentially used to guide the conservative selection of circuit elements to supply power to a motor.

The real motor in operation will almost certainly draw less current than suggested by the NEC tables, except during starting and other transients.

Perhaps you can expand your question: what are you trying to figure out, for what application?

-Jon

 

[Besoeker]

Dear sirs,

A single phase AC motor (fan) 0.3 kW (0.4 HP), 220V 50Hz, with nameplate FLA 2.2A.
I would appreciate anyone to tell me what is exact FLC of the motor?

Kind regards,
HungPV

Why would you think the full load current (FLC) is any different to the nameplate full load amps (FLA)?

In any case, 2.2A at 220V single phase gives you 0.484 kVA which sounds about right for a 0.3 kW motor.

 

[steve66]

I think the 2.2 amps could be the actual current drawn if the motor and fan were manufactured together as a unit.

But many exhaust fans are shipped with an off the shelf motor. If that's the case, the actual current draw could be somewhat less than the motors rated FLA. But it would depend on the operating point of the fan. You would probabably have to contact the manufacturer to get the exact current.

But I'm not sure why you would need the exact current.

 

[Pham Van Hung]

FLC of 1~ motor 0.3kw, 220V, FLA 2.2A

FLC of 1~ motor 0.3kw, 220V, FLA 2.2A

The real motor in operation will almost certainly draw less current than suggested by the NEC tables, except during starting and other transients.
Perhaps you can expand your question: what are you trying to figure out, for what application?

Winnie,
I am designing a power supply circuit to feed totally 95 0.3 kW fans (103 fans including spares). Overload protection, fault and short-circuit protection elements and corresponding conductors need to be calculated and choosen.

The Maximum actual measured steady-state continous current draw is 2A. (we measured by clamp ampere meter?)
The maximum measured current during start-up/transient is 7.2A.
Fans are used in assembly line for operators' cooling.

I did some inital caculations based on FLC of 4.4A and got some results but I am not sure if they are correct, so I posted here for asking supports beginning from FLC asumption of 4.4A.

Thanks and kind regards,
HungPV

I think the 2.2 amps could be the actual current drawn if the motor and fan were manufactured together as a unit.
But I'm not sure why you would need the exact current.

Steve66,
Please refer to my reply to Winnie.

Why would you think the full load current (FLC) is any different to the nameplate full load amps (FLA)?

Besoeker,
I think FLA is the rated current specified by manufacturer under rated voltage, frequency and load condition while FLC is a figure referred from motor Hp/kW and tested/specified by NEC taking into account safety factors for the purpose of selecting protection circuit elements. Maybe, I am wrong?
--HungPV

 

[Crionics]

Regardless of where the NEC values come from, you size fuse / MCP and wire per NEC tables and size the overloads per the motor nameplate values. If the nameplate value says 2.2A, I wouldn't have any reason to not trust it. It'll probably draw less than that anyway.

 

[Besoeker]

Besoeker,
I think FLA is the rated current specified by manufacturer under rated voltage, frequency and load condition while FLC is a figure referred from motor Hp/kW and tested/specified by NEC taking into account safety factors for the purpose of selecting protection circuit elements. Maybe, I am wrong?
--HungPV

Hi PVH
I'm from UK and the NEC code is not used here so I am not qualified to comment on it.. Installation methods here are usually quite different to those used in USA. Motor nameplate current is what's normally used here to size the supply installation, and protection requirements.

In any case, even the 4.4A would fall below the rating of the minimum cable size we would use so, as far as cable rating is concerned, it's a bit academic. I agree with Crionics in the last post - the motor overloads should be sized for the nameplate current otherwise they won't be protected.

But do you design the supply based on 4.4A or 2.2A....
Here, I would use the 2.2A per motor and rate the supply accordingly. Otherwise you'd end up providing a supply operating at a maximum of 50% of its rating.

Another observation/question. At 2.2A per motor, the supply will have to provide around 50kVA. Do you intend to use a 4-wire three phase 380/220V system?

And a final question. I don't know where you are from - for some reason I have it in mind that it is Malaysia and specifically KL. Whether or not that's correct, I note that your motors are 50Hz. That suggests a country with links to Europe rather than North America. If that's the case, is the NEC code the applicable standard?

 

[Pham Van Hung]

Thanks you all but I have more questions.

Thanks you all but I have more questions.

Hi PVH
In any case, even the 4.4A would fall below the rating of the minimum cable size we would use so, as far as cable rating is concerned, it's a bit academic. I agree with Crionics in the last post - the motor overloads should be sized for the nameplate current otherwise they won't be protected.

But do you design the supply based on 4.4A or 2.2A....
Here, I would use the 2.2A per motor and rate the supply accordingly. Otherwise you'd end up providing a supply operating at a maximum of 50% of its rating.

Another observation/question. At 2.2A per motor, the supply will have to provide around 50kVA. Do you intend to use a 4-wire three phase 380/220V system?

And a final question. I don't know where you are from - for some reason I have it in mind that it is Malaysia and specifically KL. Whether or not that's correct, I note that your motors are 50Hz. That suggests a country with links to Europe rather than North America. If that's the case, is the NEC code the applicable standard?

Hi Besoeker,
I am from Vietnam where European standard appllied. I tried to search for some helpful instructions from IEC/IEEE but no success. I found in NEC clear instructions and think that I should follow. Would be grateful if you can show me where to find equivalent instructions on how to design my circuit following International/European standards. I am an electrician and this is the first time I got an assignment to do this task.

Yes I use 4 wire 3 phase 380V/220V system.
I use FLC of 4.4A to size the ground fault and short-circuit protection device, and use FLA of 2.2A to size the motor overload protection device. All are clearly stated in NEC.

The results is as follows:
- for 1 motor: overload ratings is FLA x 1.15 = 2.2A x 1.15 = 2.53A and take the lower number of 2.5A (NEC 240.6 (A))
On the other hands, NEC 430.52 specifies selection of overload device ratings as FLC x 1.75 = 4.4A x 1.75 = 7.656A and take the upper number of 8A.
So there is difference btw 2.5A and 8A ratings, but 8A seems more resonable as it is higher than mortor stating current of 7.2A, while I am also concerned if 8A overload device can protect the motor overload of, for example, 5A? My answer would be not, the motor may burn out before overload device can react. For overload, I intend to use time-delayfuse.

I do not know what is guided in IEC?
Any helps are highly appreaciated.

 

[Besoeker]

Hi Besoeker,
I am from Vietnam where European standard appllied. I tried to search for some helpful instructions from IEC/IEEE *but no success.

Installation:
In UK we use BS 7671 "Requirements for Electrical Installations" for installation.

Low-voltage switchgear and control gear:
IEC60947 or BS EN 60947 in various parts

Normally, you'd have to purchase the above but if you have a good reference library, it may have copies.
I don't know if there are copies available on-line for free download but, even if there are, I'm fairly sure that would be illegal. You will thus understand that I have to advise you not to do so.

*IEEE (I triple E) is a US based institution.
The UK equivalent was the IEE (Institution of Electrical Engineers) now merged with the IIE (Institution of Incorporated Engineers) to be come the IET (Institution of Engineering and Technology).
My point here is that searching the IEEE may not be very useful for getting European standards.

 

[Pham Van Hung]

Installation:

My point here is that searching the IEEE may not be very useful for getting European standards.

Hi Besoeker,
Thanks for your more insight information.
I think there are not much diffrence btw IEC or IEEE, as we both live in an earth and both standards try to guide us how to choose devices to protect our equipment in the safe way? isn't it?

Could you please have a look at my concern in the last post?
Could you advice 2.5A or 8A fuse?
I calculate each motor a 16A MCB, 2 x 2.5mm2 conductor, and feeder of 32A for group of 6 motors, conductor 2x 8mms?
Should you have a different idea? Please advice.

HungPV

 

[Besoeker]

Hi Besoeker,
Could you please have a look at my concern in the last post?
Could you advice 2.5A or 8A fuse?
I calculate each motor a 16A MCB, 2 x 2.5mm2 conductor, and feeder of 32A for group of 6 motors, conductor 2x 8mms?
Should you have a different idea? Please advice.

HungPV

I can't give you advice. In any case it is outside the power ratings that I normally deal with. However, I can tell you how I would approach it.

We do use single-phase fans of that sort of power rating for cooling electrical enclosures or on higher current rectifiers and inverters. Mostly they have impedance protected motors which means that, even if they get jammed, they will not overheat. In such cases the only protection we use is a fuse on the line side and a link in the neutral (and air flow detection). The fuse is there to protect the wiring to the fan motor (and rated accordingly) and not to protect the fan motor itself. In our case it is all inside an electrical panel and, as a rule, powered from a control transformer which is there for other purposes.

When the motors were not impedance protected, we added a thermal overload. It is quite difficult to find single-phase thermal overloads so we used three-phase units with the three elements wired in series.

If your fan motors need to be remotely started and stopped you would need to add a contactor, the control wiring for it, and a pushbutton station. Or you might consider something like this:

As for cabling.
Your motors are rated for 2.2A per the nameplate.
From BS7671 table 4D2A (copper conductors), 1.5mm^2, 2-core is rated for 14A in a 30C ambient when installed enclosed in an insulating wall. Other installation methods give higher currents. In a 50C ambient the cable would be de-rated to just under 10A per table 4C1. To me, this would seem to be more than adequate for a 2.2A motor unless you are concerned about volt drop. This is 29mV/A/m.

For a group of six motors total current is 13.2A. On the same basis as above, 4.0mm^2 gives about 18A at 50C. Voltage drop is 11mV/A/m.

Enough.......

 

[Pham Van Hung]

As for cabling.
Your motors are rated for 2.2A per the nameplate.
From BS7671 table 4D2A (copper conductors), 1.5mm^2, 2-core is rated for 14A in a 30C ambient when installed enclosed in an insulating wall. Other installation methods give higher currents. In a 50C ambient the cable would be de-rated to just under 10A per table 4C1. To me, this would seem to be more than adequate for a 2.2A motor unless you are concerned about volt drop. This is 29mV/A/m.
For a group of six motors total current is 13.2A. On the same basis as above, 4.0mm^2 gives about 18A at 50C. Voltage drop is 11mV/A/m.
Enough.......

Hi Besoeker,
Thanks for your answers. I understand what you mean by enclosed panel cooling fan. However, our application is quite different, that is industrial fans are used in the assembly shop. They are direct- online started and manual switch on.
Your information on cable size seems to be OK, but did you take into account of starting current of fans (start current is 7.2A and if some fans are switched on at the same time it will add up to more than 18A)?
What do you think?
Regards,
HungPV

 

[Besoeker]

Hi Besoeker,
Thanks for your answers. I understand what you mean by enclosed panel cooling fan. However, our application is quite different, that is industrial fans are used in the assembly shop. They are direct- online started and manual switch on.
Your information on cable size seems to be OK, but did you take into account of starting current of fans (start current is 7.2A and if some fans are switched on at the same time it will add up to more than 18A)?
What do you think?
Regards,
HungPV

HPV

Pretty much everything I do is for an industrial setting.
A starting current of 7.2A is still comfortably within the rating of 1.5mm^2. Buried in a wall it gives you 14A. In the more usual circumstances for an industrial it would be Reference method 1 (clipped direct) or reference method 11 (on a perforated cable tray). The ratings are 19.5A and 22A respectively.