Iron Core Transformer and Frequency in UPS

[thetrueman]

Hi all,

I just want to know that at which maximum frequency an Iron Core Transformer can work? Actually I want it in UPS with PWM 220V 50Hz.

Shahzad

[sam_des]

Hello,

Well, that depends on Iron Core type, wire guage, winding methods, temprature rise you can afford i.e Your Trasnformer design. Personally I've done UPS/Inverter designs upto 20kHz with iron core transformers.

Most commercial designs available in Asia(read India, Pakistan,China etc) are based iron core transformers but use frequencies upto 5-6kHz. This produce humming noise from transformer which can be very annoying. So it is better to go atleast upto 10kHz to minimize audible noise.

regards,
sam_des

[Walkura]

Last year i been working on a pwm true sine inverter .
More or less by coincidence i saw that my 20 Khz carrier came through a standard iron ringcore crispy and clean .
After a little research i learned this.
For higher frequency's in iron core transformers they developed laminated iron with a certain amount of silicon .
From what i was told metalcores at high frequency's can suffer from metal fatigue .
So if you can get a hold of the datasheet of the core used pay some attention to those figures .
For my experiments the iron core did better then expected .
(although i temporary had to stop the project by lack of time for now its still on the shelf)
I would just give it a go .
Just be carefull eventhough a ironcore usualy runs at a higher T then ferrites you can still saturate them
I found that out with a 500 Watt core and it made me a nice blackspot on my desk 

[POWERMAN]

Hello,

Ferrite is usually a best choice for inductors designed to operate in the discontinuous mode at frequency about 50KHz when core loss associated with large flux swing limits core utilization.
However, in the continuous mode, with small ripple current and small flux swing, ferrite cores will often be limited by saturation.
In this case lossier cores materials with greater saturation flux density such as powdered irons, Kool-Mu, Permalloy powder or even gapped laminated metal cores may enable reduced cost or size.

[ajmain]

The more turns you give, ie, the higher the transformer inductance, you can apply higher frequency to the transformer. Personally, I've read somewhere that if the inductance is 40H then, you might apply 40kHz to the transformer. But it is just a waste. Unless you're working with low frequencies, its (way) better going for ferrite core (cheaper, less turns, and so on...).
Hope this helps.

[tAhm1D]

Hi all,

I just want to know that at which maximum frequency an Iron Core Transformer can work? Actually I want it in UPS with PWM 220V 50Hz.

Shahzad

Hi,
It depends upon the method of use of Iron Core Transformer. Let us take the example from your required UPS. If you want square wave output you can use Transformer directly with Push pull or Full bridge Topology to get the required output with direct use of Transformer and your input may be 12/24V Battery. In this way you can use Iron Core Transformer upto 400-600Hz max. efficiently.
On the other hand if you use Transformer indirectly,like for obtaining sine wave output, you can use Iron Core Transformer upto 20KHz(I have used upto 20KHz). Here, you are using modulation and demodulation. Here, you are creating 20KHz carrier frequency with PWM-ed IC and demodulate it before the Transformer with Low Pass Filter and send Sine shaped 50 Hz to the Transformer to convert it 220v sine wave output.
These are 2 ways to use Iron core Transformer in Low and High Frequency. Other ways are there to use Iron Core Transformers in high frequencies but those are not practical in nature. For high frequency direct use in Transformer, it is wise to use Ferrite Core Transformers.