American built motor to run on Australian mains

[1Marc]

Hi there!
I am sure this has been asked before.
I can not source a local supplier of Forge Blower down under yet there are several to chose from in the US. Of course the usual 110v / 60hz hurdle applies.
One of the manufacturers "Dayton" has several models that state 230v 60/50 hz. Now that seems to fit what we have here as mains supply, namely 240v 50 hz

http://www.electricmotorwarehouse.c...230v-60-50hz-2c915/#sthash.UXvjlhEp.dpbsAfter

some local enquiries with disparaging replies tell me no one really knows if this is OK or not for Australian supply.
What say you guys?

Your reply is appreciated.
Marc

 

[waross]

Yes and no,- in your case probably no.
The motor will run, but slower.
A 60 Hz 1760 RPM motor will run at about 1460 RPM on 50 Hz.
The voltage should be adjusted in a 5/6 ratio.
A standard NEMA motor will be rated at 230 Volts for use on a 240 volt system. (A multiple of 115 volts for motor ratings, multiple of 120 Volts for system voltages).
So on 50 Hz, the motor will be rated at 192 Volts for a system voltage of 200 Volts.
The rated current will be the same, the torque will be the same, the voltage and the speed drop in the ratio of 5/6.

Now the bad news. If this motor is driving a blower you may not get acceptable performance from the blower at the reduced speed.

The solution;
With a system voltage of 240 Volts, drop in a VFD to drive the motor at 60 Hz.
The good news is that you will NOT need transformers to drop the supply voltage to 200 Volts. Put the money saved on transformers towards the purchase of a VFD.
On the other hand, if this is a single phase motor, the solution becomes more challenging.
(If the equipment will function properly at reduced speed, then just drop the voltage to about 200 Volts.)


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

 

[mvcjr]

The voltage ratings has to be based on a volts/hertz ratio. A 230V, 60Hz motor has a V/Hz ratio of 3.833. When used on a 50Hz system, the motor is rated only for 192 volts like waross mentioned above.

 

[itsmoked]

Internationalize your product by switching to a cheaper and about 5 times more reliable three-phase motor and include a hundred dollar VFD that will will take single phase power and put out the needed three phase as mentioned by waross. It will improve the product by allowing accurate speed adjustment to allow fine adjustment of the flame level. Using the native inputs, even the most base VFD has, you can provide all sorts of fancy features like; High Heat, Idle Pile, Tempering, Melt Down, and anything else you want with the press of a button or even a wave of the hand.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jraef]

I disagree, sorry.

If the motor mfr lists it as suitable for 50/60Hz, they have designed the blower for that. Yes it will run slower, but it will run at the speed all motors run at in your part of the world, that shouldn't be a surprise for you. Most likely they rate it 50/60Hz knowing this, because at 5/6 (83%) speed, the centrifugal blower load expressed on the motor at that speed will drop by the cube of the speed change, so 57% load (look up Afiinity Speed Law). Yes, at the reduced Hz the V/Hz ratio is going to be higher so the motor would run hotter at the same load (compared to 60Hz operation), but the load on the motor becomes so much lower at 50Hz that the added core heating becomes irrelevant.


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

 

[1Marc]

OK ... you had me scratching my head for a while there ... If Dayton states 230V 60/50 HZ that means in my ignorant interpretation that it is suitable to be used on 60hz or 50hz or otherwise why would they list it that way?

In other words, they are meant to be sold to countries other than the US, those that use 50HZ
Am I wrong?
By the way if you wonder why I am asking you guys rather than the manufacturer, you are right ... but manufacturers in my experience either do not answer at all of have a stock reply written by their solicitor.

And it is a single phase motor of course, so how can I use a VFD? Aren't they for 3 phase? Sure buying a 3phase blower would be grand, but we have 415V in 3 phase not 380V and an industrial blower will cost a bomb. The blower I am after is a little more than a bathroom fan, only centrifugal rather than axial.

Now to the part that confuses me the most. I understand that a small variation in Voltage is no big deal. We have nominal 230V but do run up to 240V sometimes and I have European motors made for 220V (50hz) that run happy on our 230~240V supply.

"Your" 220V (US) is it any different from any other 220V supply disregarding the frequency? I read that you split (?) to obtain 110V and I only split firewood so any explanation is welcome.

 

[waross]

A 240 Volt transformer winding is center tapped to derive two 120 Volt sources in series.
Looking at the specs for that motor, It appears that when driven with 60 Hz, the fan load increases and limits the speed to not much more than the 50 Hz speed.
eg:
50 Hz speed: 2700 slip = 300 RPM
60 Hz speed: 2880 slip = 720 RPM.

So it appears that they are running the motor near the motor torque limit and letting the fan load limit the speed.
With an integral HP motor this would be wasteful and inefficient.
To use an integral motor in this fashion, The current may be 200% of normal running current. This can be done if the wire gauge is increased to carry the greater current without overheating.
But that means a larger core, which means more wire again.
In practice you could design the motor for about 340 or 350 Volts and then run it on 230 Volts. Same result.
Possible but prohibitively wasteful.
But this is a 1/30 HP motor. In a motor this small, it is not costly to allow the load torque to limit the speed and use very high slip frequencies.
Consider: A 1760 RPM motor has about 2.2% slip.
This motor has 10% slip at 50 Hz and 20% slip at 60 Hz.
You can use such a design easily at 1/30 HP, but not at higher HPs.
BTW, There as a 230 Volt version of this motor available so no need to worry about 115 or 120 Volts..

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