Physical volume estimate: DC-DC convertor of ~250W - Page 1
Forum section: electronics / projects

author: max_torque
author_rank: Super Contributor
timestamp: June 13, 2015, 01:16:39 pm
content: I have an existing industrial system that has a nominal 12v supply voltage, and runs several DC brushed motors (motors are around 12A @12V under full load, 244W).I have been asked if it is possible to "Overspeed" one of the motors , which would require a supply voltage of about 16V. Being a brushed motor i can't use techniques like field weakening etc, so i must raise the supply voltage (can't get existing motors rewound for more KE, unless we go to custom winds, which the client doesn't want to do) And unfortunately, the 12v supply is also shared with a lot of other things, and so the simple option of bumping up that supply voltage isn't an option.This leaves a DC:DC option. Not being experienced in this field, how do i go about estimating the physical size(and cost) of such a device?(fundamentals such as convertor topology, switching frequency, inductor type, acceptable ripple etc etc are all undecided at this time.........)

author: max_torque
author_rank: Super Contributor
timestamp: June 13, 2015, 01:18:40 pm
content: Oh, yeah, should have added:Having an output voltage control between 0 and 16v would be nice, to allow speed control of the load motor!(ie convertor needs to be a buck&boost architecture)

author: amyk
author_rank: Super Contributor
timestamp: June 13, 2015, 01:22:26 pm
content: Look at a high-end PC power supply for a volume estimate - they can provide much more than 250W.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 13, 2015, 01:57:44 pm
content: If you want to boost the supply from 12V to 16V at 20A , your DC-DC only needs to be rated at 4V@20A, i.e. 80W, as you can stack the output on top of the incoming 12V.You could do it with one of these :http://www.digikey.co.uk/product-detail/en/UQQ-5%2F17-Q12PB-C/811-1892-5-ND/1980350

author: max_torque
author_rank: Super Contributor
timestamp: June 13, 2015, 04:43:40 pm
content: What about getting a controllable output voltage that can go below the supply rail?Ie, a buck convertor, but with a boost convertor in front of it?

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 13, 2015, 04:58:54 pm
content: Buck then boost allows you to share the inductor.How much power do the other 12V loads use? If it's small compared to the motors, it might make more sense raising the supply voltage and then adding a regulator for the 12V loads.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 13, 2015, 05:05:51 pm
content: Quote from: max_torque on June 13, 2015, 04:43:40 pmOr a simple boost with simple PWM to control the speed - remember we're talking motors, not something super-sensitive

author: zapta
author_rank: Super Contributor
timestamp: June 13, 2015, 07:09:54 pm
content: Quote from: mikeselectricstuff on June 13, 2015, 01:57:44 pmThat's a clever solution.

author: max_torque
author_rank: Super Contributor
timestamp: June 13, 2015, 08:27:03 pm
content: Quote from: NiHaoMike on June 13, 2015, 04:58:54 pmGot a link to a schematic for that^^^ ? Can't quite picture it

author: f5r5e5d
author_rank: Frequent Contributor
timestamp: June 14, 2015, 05:28:16 am
content: PC power supplies will give you a unfortunate overoptimistic idea of the tech - anything made by the Millions has a much different cost than a commercial purpose built in low volume or even worse a inexperienced engineer's one-off from a sw chip datasheet/app notedo you want a switch mode amplifier that can vary to beyond the input supply?SEPIC and CUK have continuously variable output - but CUK inverts in simplest formor a fixed output sw mode converter with whatever your control amp is now?