SMPS design for peak power or average?

[joeltang]

Hi everyone, first post here. I've been buried in paperwork studying SMPS designs now for the past few months and I have not been able to answer this practical question.

I need to design a power supply with 10KW continuous with short duration bursts of 22kW required.

Should I stick to a 10KW design or go for peak power?

Cheers,

 

[CobraNet]

Hi everyone, first post here. I've been buried in paperwork studying SMPS designs now for the past few months and I have not been able to answer this practical question.

I need to design a power supply with 10KW continuous with short duration bursts of 22kW required.

Should I stick to a 10KW design or go for peak power?

Cheers,

Very intresting project indeed, do you have any plans about the design, topologies?

is it 3 Phase design?

whats the use of this thing?

 

[joeltang]

It's for electric vehicle conversion. I have a 3 phase 10hp motor that I will drive with a 30hp controller. I've purchased both of these, and have hit a snag in that my controller's bus voltage would ideally be at 650Vdc.
I'm not ready to drop the $2K required for lithium cells.
I have a cheap source of lead acids but they weight 30lbs each.
Putting 56 cells X 30lbs gets over my Chevy Metro's weight target by far.
If I could boost from a lower voltage I would be able to reduce the amount of cells required as my duration requirements are light.

At this stage I'm not locked into any particular topology but I've been leaning towards a full bridge DC-DC or a interleaved boost regulator.

I have though about making use of a dozen salvaged microwave oven transformers in parallel to meet my power requirements and provide the large differential in voltage. I measured a few of these to be about 16:1.
They are typically 1kw each and if I keep the switching frequency at about 40khz I'm hoping the iron core transformer loss will be tolerable. I still have some doubts about this approach and am actively looking into winding my own transformer.

I'd like to get away with about +70% efficiency if possible.

An online tool at www.poweresim.com spits out this schematic when I plug in my requirements: http://goo.gl/akeHg

I work in electronics engineering for over 10 years, but mostly low power. I have training with high power and am comfortable with this high power project. This is not for everyone!!

 

[joeltang]

schematic link I used didn't work.
Here it is: http://goo.gl/akeHg

 

[MicrosiM]

I am not sure what is the specifications of your application, let me know some details so I can guide you in the right direction, hopefully

 

[hilli_billi]

Hi Joel,
You want to drive 10HP motor by a 30HP controller, that's ok. Is HP horse power? (sorry I'm German). 1 HP = 0,745 kW, So for your 10 HP motor a 10kw controller fits.
Wat is the voltage of the motor/controller you already have?
How do you get a rail voltage of 600V ?

 

[joeltang]

Hi Joel,
You want to drive 10HP motor by a 30HP controller, that's ok. Is HP horse power? (sorry I'm German). 1 HP = 0,745 kW, So for your 10 HP motor a 10kw controller fits.
Wat is the voltage of the motor/controller you already have?
How do you get a rail voltage of 600V ?

yes, hp=horse power so 7.45kw controller would do but its the power supply t
requirements that I'm unsure of.

my 30hp controller has voltage alarm thresholds of
550 to 800 volts because it rectified 480v 3phase.

 

[Redwire]

Why are you running such high voltage for a 10HP motor? Prius went from 274V to 202V, Chevy Volt is 300V battery pack. Although current and I^2R losses go down at higher V, then you get losses in the DC bridge converter and then you have to use 1200V IGBT's which are wasteful with their Vsat.

An old Solectria controller I worked with had around 170VDC input for 10HP, and used MOSFETS for the 3-phase H-bridge. It was in a Ford Escort station wagon, with nicads, as a university project. It did really well but the mosfets tended to blow with a freshly charged battery pack 200VDC.

Back to your original question, I would suggest design rated (semi's) for peak power but heatsink/PCB for max. average power. You can't get 22kW out of the battery pack for long, but when passing a car nobody likes to blow a semiconductor!

 

[joeltang]

Why are you running such high voltage for a 10HP motor? Prius went from 274V to 202V, Chevy Volt is 300V battery pack. Although current and I^2R losses go down at higher V, then you get losses in the DC bridge converter and then you have to use 1200V IGBT's which are wasteful with their Vsat.

An old Solectria controller I worked with had around 170VDC input for 10HP, and used MOSFETS for the 3-phase H-bridge. It was in a Ford Escort station wagon, with nicads, as a university project. It did really well but the mosfets tended to blow with a freshly charged battery pack 200VDC.

Back to your original question, I would suggest design rated (semi's) for peak power but heatsink/PCB for max. average power. You can't get 22kW out of the battery pack for long, but when passing a car nobody likes to blow a semiconductor!

Thanks for your answer. Sounds very sensible.
My reason for high voltage: I just had a great deal on a 22kw controller that is a 480v 3phase. Claiming a loss to switch controllers is the only thing stopping me from dropping the voltage. I'm contemplating changing the voltage sensors to allow for less but I'm far from figuring out how this could be done. I also worry that my current would become too high for the same power.

 

[Kanwar]

You need a continuous rating of atleast 1.2X times that of a motor in fully loaded condition. But at that same time you need a peak power rating which should be based on the starting current of motor.