Transformer question: 50Hz versus 60Hz

In summary: Definitely helps to visualize what's going on with these devices.In summary, a transformer with 60 Hz being fed to a 50 Hz supply will work, but the voltage at 50 Hz has to be 20% less than the 60 Hz voltage.
  • #1
jojo13
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1
Will a transformer with 60 Hz being fed to a 50 Hz supply work?
 
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  • #2
The transformer flux capability is related to the ratio, V/Hz. So for a given voltage rating at 60 Hz, the capability at 50 Hz will be 20% lower, or I mean the voltage at 50 Hz has to be 20% less than the 60 Hz voltage.

So you can't operate with the same voltage rating on 50 Hz as you have at 60 Hz or the core will saturate.

A common 60 Hz voltage is 480 V. That gives you a V/Hz ratio of 8. A common 50 Hz voltage is 400 V, which gives you the same result, so you can use a 480 V 60 Hz transformer on a 50 Hz system if the voltage is 400 V.
 
  • #3
a transformer designed for 60 Hz can be supplied by 50 Hz as long as the V/Hz ratio is preserved.

In other words, V60/60 = V50/50

where V60 is the 60 Hz voltage and V50 is the 50 Hz voltage

To preserve the ratio, V50 = 5/6 * V60

so the 50 Hz voltage has to be 83% of the 60 Hz value.Going the other way, a transformer designed for 50 Hz will have the result

V60 = 6/5 * V50

or - 1.2 * V50

So a 50 Hz transformer can definitely handle the same voltage at 60 Hz.
 
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  • #4

Ahh I get it. So no matter what, a 50 Hz can be fed to a 60 Hz
 
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  • #5
Correct!
 
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  • #6
jojo13 said:
Ahh I get it. So no matter what, a 50 Hz can be fed to a 60 Hz

What is your background, @jojo13? Have you had calculus yet ?

@magoo gave the correct answer.
The why behind it is

A transformer core is sized to carry the magnetic flux necessary to support the voltage you're going to impress on its windings.
Since in any inductor the relation between volts and flux is a derivative-integral one,
volts = -number of turns X d(flux)/d(time) ... or flux = 1/n X ∫volts X d(time)
volts per turn is a measure of the rate of change of flux in the inductor

It is most easily visualized with a square wave voltage

core50ACsq_wav2annotated.jpg


As the equations show, the integral volt-seconds is a measure of the magnitude of that flux at any instant.
See that flux increases while voltage is positive and decreases while it's negative? That's Mother Nature at work doing real world integrating. Maths Rule !

Okay, so the longer voltage stays positive the higher flux rises.And vice versa.
On a 60 hz power system voltage stays positive for 8.33 milliseconds, a half cycle With a 100 volt square wave that'd be 0.833 volt-seconds.
On a 50 hz power system voltage stays positive for 10 milliseconds. With a hundred volt wave that'd be 1 volt second.
Some power inductor datasheets give the volt-second rating.

Point is the core must be large enough to hold all that flux.
If it's not , excessive magnetizing current will flow trying to force more flux through a core that's already full. That heats both the iron core and the copper windings. You'll hear the core 'buzz' from magnetorestriction.

here's a picture i drew for another thread some years ago..
This core is "full of flux" at the orange line.
Pushing flux all the way up to the required volt-seconds requires excessive magnetizing current and will soon overheat that inductor.

core50ACsq_wav4.jpg


I hope that plants the basic idea and sparks an interest in inductance for you.

Train your brain to think in terms of derivative-integral relationships. Mother Nature loves them and it'll help you appreciate the magnificent world she's built around us..

Now in a power system you'll have sine waves not square.
Derivative of sine is cosine which has same shape , so it is not obvious by just looking that integration-differentiation is at play.
That's why i prefer to explain with square and triangle waves it makes it obvious to the eye.
Here's a 'scope trace of a real inductor with triangle wave current forced through it(top trace) - observe voltage is almost square(bottom trace).
That core was rather a poor one hence the rounded corners on the voltage wave

triangle_current_sec_volts3HZonly.jpg
Here's an image of a transformer's current when it enters saturation. That could happen from using a 60 hz transformer at 50 hz if you don't decrease applied voltage. (image courtesy of https://www.rane.com/note159.html check it out )
upload_2018-8-26_9-34-18.png


Observe current peaks not at voltage peak , but after it when volt-seconds reach the limit of the core.
That transformer will soon be in trouble. I guarantee it's buzzing.

I hope the above long, non-mathematical tome helps someone 'see the light'. That 'scope trace was an "AHA! moment" for my technician and me.
When your intuition leads you to the same formula that's in your textbook it's the start of real understanding.

old jim
 

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  • #7
Thanks Old Jim. We all love learning from you.
 
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  • #8
Thanks @anorlunda

if i can help somebody relate those erudite derivations in their textbooks to the physical goings on it is worthwhile.

Thank you guys for tolerating this math challenged old fossil.

old jim

ps - viva Faraday !
 
  • #9
jim hardy said:
ps - viva Faraday !

viva Steinmetz!
 
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  • #10
I agree with those comments, Old Jim. You add a lot of meat to the bones!
 
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  • #11
jojo13 said:
Ahh I get it. So no matter what, a 50 Hz can be fed to a 60 Hz
Keep in mind core loss is also affected, so putting a 50Hz transformer on a 60Hz line with the same flux swing will result in 20% increase in core heating.
 

1. What is the difference between 50Hz and 60Hz?

The main difference between 50Hz and 60Hz is the frequency at which alternating current (AC) electrical power is transmitted. 50Hz means that the electricity is alternating 50 times per second, while 60Hz means that it is alternating 60 times per second. This difference in frequency can affect the performance of certain electronic devices, such as transformers.

2. Which frequency is better for transformers, 50Hz or 60Hz?

This depends on the specific application and design of the transformer. In general, 50Hz is better suited for larger transformers, while 60Hz is better for smaller transformers. This is because 50Hz requires larger and heavier components in the transformer, while 60Hz allows for smaller and lighter components.

3. Can a 50Hz transformer be used with a 60Hz power supply?

Yes, it is possible to use a 50Hz transformer with a 60Hz power supply. However, the transformer may not perform as efficiently as it would with a 50Hz power supply. This is because the transformer is designed and optimized for a specific frequency, and using it with a different frequency can result in decreased efficiency and potential overheating.

4. How does the frequency affect the voltage output of a transformer?

The frequency of the power supply does not directly affect the voltage output of a transformer. However, the frequency can indirectly impact the voltage output by affecting the transformer's efficiency and performance. As mentioned before, a transformer designed for 50Hz may not perform as well with a 60Hz power supply, which can result in a lower voltage output.

5. Are there any safety concerns when using a 50Hz or 60Hz transformer?

There are no specific safety concerns associated with using a 50Hz or 60Hz transformer. However, it is important to ensure that the transformer is properly rated and compatible with the power supply frequency to avoid potential issues and hazards. It is always recommended to consult with a qualified electrician or engineer for proper installation and usage of transformers.

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