How to know what maximum Volts/Amps I need on a PSU ? - Page 1
Forum section: electronics / beginners

author: anonono
author_rank: Newbie
timestamp: October 12, 2020, 12:57:34 am
content: Hello,I know nothing on hardware butI'll need to power 12 up to 37 motors, at the same time.It may be those oneshttps://hobbyking.com/en_us/9235-100kv-turnigy-multistar-brushless-multi-rotor-motor.html?___store=en_us, even though I don't even know if it's normal that the maximum torque appears nowhere in the specs.What worries me is that it's written on that websiteQuote,1) this means it's not the peak max current they could drain ?2) Correct me if I'm wrong but in the worst scenario I should consume 10V if they're all 10V and 12 up to 37 times 1A if they're all 1A ? Which leads to a PSU pushing 37A at 10V ?3) Why do I usually see high Voltage capacity PSU but never above 10~12A ?By thanking you for your knowledge

author: rstofer
author_rank: Super Contributor
timestamp: October 12, 2020, 01:59:24 am
content: They give you 2800 Watts and 57A so they must assume 49V max.For 30 motors you might need to provide 84 kW and that's a LOT.In broad terms, those are 3.5 HP motors. Thirty of them would take 700A at 120V - about 6 houses worth of service entrance. They would take just 100A at 480V 3 phase if you are inside an industrial buildling.

author: radiolistener
author_rank: Super Contributor
timestamp: October 12, 2020, 02:26:48 am
content: Quote from: anonono on October 12, 2020, 12:57:34 amyes, this is minimum current for the case when there is no load on the motor (idling mode)37 motors will consume 10V 37A in the best caseQuote from: anonono on October 12, 2020, 12:57:34 amNo. Max power is specified as 2800W and 57A. It means about 2800/57 = 49V.At worst case, for 37 motors, you will need 50V 2109A power supply. This is about 106 kW power.Quote from: anonono on October 12, 2020, 12:57:34 amBecause 10-12A is a high current. If you needs more Ampers, it turns dangerous and requires dedicated power supply. This is dangerous, because current more than 20 Amps can make fire and can damage circuit and PCB. So it needs special care, special wires and special equipment. Because usual wires and circuit is not intended for so high power.37 motors will require more than 100 kW power. This is too much and such power is very unsafe, it can make high fire and high damage and can kill you easily despite the low voltage. It can kill people or make serious injury with high temperature, fire and high mechanical force.

author: WattsThat
author_rank: Frequent Contributor
timestamp: October 12, 2020, 02:39:35 am
content: Not sure what you plans are but understand these motors absolutely need propellers to provide air flow, otherwise they will burn up in no time all without large quantities of airflow.The voltage required is dependent upon how fast you want them to turn. The rating is 100kv so you get 100 rpm per volt. They are spec’ed for 8 to 12 cells so that is nominally 32 to 48 volts. That will result in a speed range of 3200 to 4800 rpm.The rating of 56 amps is a peak number, that could never be maintained as those motors would smoke in seconds at that current. The 1 amp at 10 volts is what the motor draws with no load, this is no propeller.The actual amps required by the motor is a function of the propeller pitch. Since they don’t provide that data, you really have no way to know what the current requirement actually will be until you load one up and measure it. They’re designed for batteries and the bigger they are, the longer they run.Whatever it is you’re thinking of attempting to do, it’s not practical and probably not possible.

author: Brumby
author_rank: Unknown
timestamp: October 12, 2020, 03:21:13 am
content: There is one question that nobody has asked yet....Out of curiosity - what were you going to do with these motors?

author: anonono
author_rank: Newbie
timestamp: October 12, 2020, 03:42:48 am
content: Sorry for not having precised, it's for hacking them in building servos.I found that for 200 additional € I can get a standalone servo 48V 5A 4kg.mSo I guess I need a 6010 variable bench PSU for experimenting with 2 motor setups and then become rich or work for world companies in order to try what I wantI'll investigate the stacks of PSUs for now, thank you for confirming me some rules

author: wizard69
author_rank: Super Contributor
timestamp: October 16, 2020, 05:39:12 am
content: Honestly before hacking anything or buying anything, you really should brush up on basic electronics. The power levels you are talking about are high enough to be dangerous in numerous ways. I'm talking both mechanical dangers and electrical. Electrical dangers as pointed out are many but a big one is the risk of fire if you don't size components correctly. Also once you get above about 24 VDC the risk of electrocution from high voltage DC goes up considerably.In my opinion you are jumping into the wrong end of the pool here. Best to protect yourself and frankly those around you with a careful approach to learning electronics and motor control.