Motor's power - Page 1
Forum section: electronics / beginners

author: fabiodl
author_rank: Frequent Contributor
timestamp: October 18, 2017, 01:57:15 am
content: I was looking at a motor, specifically thishttps://www.aliexpress.com/item/DC-12V-150W-13000-15000rpm-775-motor-High-speed-Large-torque-DC-motor-Electric-tool-Electric/32813102823.htmlThe rated current is 0.32A. The rated output power is 150W.At 12V, a current of 0.32A gives 3.84W of input power. Which is nearly two orders of magnitude lower than the rated output power, and losses are not considered.My guess is that the power is limited to instantaneous conditions. However, is it normal to express the motor power in this way?What should I search for if I want to continuously have (possibly with a gear box) 1000rpm, 0.5 Nm ?

author: joeqsmith
author_rank: Super Contributor
timestamp: October 18, 2017, 02:26:54 am
content: They don't give you much do they. Not even mechanical dimensions that I could find. I believe the 150W output power. I would think they would give you at what RPM you have the 150W.I've got a little 70W toy motor I was playing with. At 14,000RPM, they claim 53% efficient. I would expect your motor to draw several Amps.

author: Awesome14
author_rank: Regular Contributor
timestamp: October 18, 2017, 04:05:30 am
content: In the United States, motor output power is = input power x efficiency. Obviously, Chinese ratings are a bit on the optimistic side. I purchase a 800mW diode laser from a Chinese dealer, and it's actual output is 10mW.In China, anything metallic gold colored can be sold under the namegold. So, many supposedlygold platedconnectors from China are not really gold plated. On eBay, Chinese dealers are required to comply to American/Western European labeling practices.

author: schenkzoola
author_rank: Unknown
timestamp: October 18, 2017, 04:18:57 am
content: I suspect the 0.32 amps is a typo. It is probably more likely 32 amps. Despite the cooling fan, I would not expect that to be continuous duty at 150W output. It has the appearance of a typical cordless tool motor.

author: rstofer
author_rank: Super Contributor
timestamp: October 18, 2017, 04:43:58 am
content: The specs say it is brushless. Really?Somehow I got the idea that brushless motors were 3 phase yet this motor has only 2 terminals.The specs also say the motor is totally enclosed but the pictures on the linked page don't show an enclosed motor.I probably have this wrong...

author: fabiodl
author_rank: Frequent Contributor
timestamp: October 18, 2017, 08:29:38 am
content: Thank everybody. Indeed, it does not seem brushless to me either.I didn't think about a typo, but yes, 32amps (instantaneous) seem a much more reasonable figure.I would like to think 150W is real, but isn't it too cheap?

author: viperidae
author_rank: Frequent Contributor
timestamp: October 18, 2017, 09:01:08 am
content: Maybe 0.32A no load current?It's definitely not brushless either.

author: joeqsmith
author_rank: Super Contributor
timestamp: October 18, 2017, 11:38:17 am
content: Looking at the motor current for the toy 70W motor, I was doing pulls up to 17A. Does seem like a typo on the decimal point.

author: james_s
author_rank: Super Contributor
timestamp: October 20, 2017, 11:09:41 pm
content: I suspect most of the specs are probably just copy/pasted from somewhere and have little basis in reality. Certainly you cannot get more mechanical energy out of the motor than you put in electrically. The current will vary with load but even at no load I would expect it to pull more than .32A. It's definitely not a brushless motor, you can see the brushes through the cooling slots.

author: Audioguru
author_rank: Super Contributor
timestamp: October 20, 2017, 11:44:12 pm
content: Ali is a Chinese website. Their sellers know nothing about Engrish, erectronics or erectricity.Of course the motor has brushes that soon wear out and might be able to provide 50W for a few seconds at 9A.