High power SMPS design.

[Jim McPherson]

Hi,
I usually hang out in the loudspeakers section, but now have a new project that requires a high powered isolated SMPS. Here are my specs:

Input 220V 60HZ
Output 1: 25VAC / 200A max, adjustable 5-200A
Output 2: 150VAC / 60A max, adjustable 5-60A

The outputs will never be used at the same time. The more square wave the output, the better.
I'm planning on using a 1200v 300amp IGBT half-bridge, or if needed H bridge.
PFC would be nice.

I'm an EE, but don't have a ton of experience in power electronics. Are there any suggestions for places to look for finding optimal switching rates? How about a source for info on selecting an output transformer size / material? Any good genearl SMPS design websites? Any other bright ideas?

-Jim

[star882]

Originally posted by Jim McPherson
Hi,
I usually hang out in the loudspeakers section, but now have a new project that requires a high powered isolated SMPS. Here are my specs:

Input 220V 60HZ
Output 1: 25VAC / 200A max, adjustable 5-200A
Output 2: 150VAC / 60A max, adjustable 5-60A

The outputs will never be used at the same time. The more square wave the output, the better.
I'm planning on using a 1200v 300amp IGBT half-bridge, or if needed H bridge.
PFC would be nice.

I'm an EE, but don't have a ton of experience in power electronics. Are there any suggestions for places to look for finding optimal switching rates? How about a source for info on selecting an output transformer size / material? Any good genearl SMPS design websites? Any other bright ideas?

-Jim

For the 25V output, you'll be better off using MOSFETs instead of IGBTs. 200A is a lot of current for semiconductors to handle, although the power electronics in electric cars have handled even more. For the 150V output, IGBTs are probably the way to go.

[Bootstrapper]

Well, if you have limited experience in power electronics, you took a rather respectable project to start with!

I've found the following books informative:
-Fundamentals of Power Electronics (Erickson et al.)
-Transformer and Inductor Design Handbook (McLyman)
-Switching Power Supply Design (Pressman)
-Practical Switching Power Supply Design (Brown)
-Switchmode Power Supply Handbook (Billings)

If you have access to IEEE papers, there are plenty of very high-power designs presented. I'm sure you'll find what you're looking for right there!

From the specs you gave I would agree with you that you'd better start with appropriate PFC stage. There might be even commercial ones available, don't know about costs though. The PFC stage might give roughly 380 Vdc (from 220 Vac input) from which the required square wave outputs can be made. Try searching for square wave inverters! The books listed above mainly discuss converters with DC output, but there are many similarities with inverters.

Other books with inverter-related topics:
-Modern Power Electronics and Drives (Bose)
-Power Electronics and Drives (Mohan)
-Power Electronics: Converters, Applications and Design (Undeland et al.)

Happy days!

[Jim McPherson]

Thanks for the suggestions. My end goal is to have DC out, but it doesn't have to be clean at all. A simple bridge rectifier and 2000uF of capacitance is all I need.

Do you suggest MOSFET's due to the lower Vce only? The reason I ask is that I don't need a super high switching frequency, and I already have the IGBT's and would like to use what I have.

I'll take a look at those books, thanks again for the tips!

-Jim

[Bootstrapper]

IGBTs should be fine, just keep the switching frequency low enough. It will lead to bulky filter components but if size doesn't matter, you'll be fine. What limits the use of MOSFETs is the maximum voltage stress: MOSFETs are superior at low voltage levels, but at roughly 500 V IGBTs might be better. Depends very strongly on operating conditions!

[Eva]

What kind of load does have such voltage and current requirements?

[Trevorferns]

the first spec seems more like a welding machine requirement to me.

[Bakmeel]

Jim,

Do you need galvanic isolation between mains and output?

Bakmeel

[peranders]

Jim, I have worked in a company which manufactured PSU's up 50 kA and 140 kV and recently I worked at a mega multi billion dollar company and in the power solutions department. With my 20 years in the business I would say that your design is nothing you will create at home unless you are an expert and has resources. Sorry to be a bit negative but this is my point of view.

[marce]

I agree with Peranders, building a PSU of this power is not a realy a home project. The max power is 5kW, even at 95% efficency youll have a lot of heat to disperse. The harmonic distrotion on your mains at those levels is somthing else you will have to consider, EMC will be an issue, a square wave is made up of numerous sine wave harmonics, it is the higher harmonics that cause the most EMC problems.
Apart from that there is SELV, CE etc standards relating to safe working voltages, a mains powered SMPS can have DC voltages in excess of 340Vdc, at the currents you want to handle electrocution or fire could be a problem.
For a commercial design it would be a minimum of a 2 board system, low voltage control and the power section, galvanic isolation between the two would be prefferable. The power board would be 4oz rolled copper min ( not readily available for DIY, and not cheap), PCB thickness will be above norm as well, quite often these pcbs end up 3.2mm to get the required copper planes and carry the wieght of some high power components, they can be beasts
On the fun side, during testing and building, when somthing goes wrong its spectacular and with burnt components and cremated PCB very very smelly!