# What is the internal difference between motors of differing wattages?

Discussion in 'General Electronics Chat' started by Transatlantic, Apr 28, 2016.

1. ### Transatlantic Thread Starter Member

Feb 6, 2014
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Say for example a company provides a vaccum cleaner in a 1400w basic and a high powered 1800w? what makes a motor draw more power?

Power = V*I, so assuming the voltage is the same, the current must have increased. To increase current, you need to reduce resistance. So what exactly changes in the higher powered motor?

Is artificial resistance added to the lower powered motors so that they dont have to be built as well, cutting down costs, hence it being cheaper?
And less artificial resistance added to the higher powered motors, meaning they need to be built better, as such increasing costs, hence it being more expensive?

2. ### WBahn Moderator

Mar 31, 2012
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This is like asking if a 200 hp engine is the same as a 400 hp engine except with artificial fuel restrictions in the fuel lines since to make more power must require more fuel. The answer is that the 400 hp engine is designed to deliver more power and a consequence of doing so means that it consumes more fuel (in general). The same with electric motors -- a higher power motor is designed to deliver more power and, in doing so, consumes more current. Part of that design MAY be lowering the winding resistance but not so much as a means of increasing the current draw, but as a means of allowing the current draw to increase. There's a difference. It's like building a table to hold a certain amount of weight. If you want to be able to put more weight on it than that, you have to build a stronger table -- but building a strong table does not automatically mean that it has more weight on it, only that it is capable of holding more weight than the lighter table. The actual current that a motor draws is primarily dictated by the electromagnetic behavior, though it can't draw more than what the resistance limits it to.

Jul 18, 2013
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A AC vacuum motor, typically is a Universal motor, armature and field are in series, hence a higher current field with lower resistance motor will exhibit a corresponding increase in torque.
Torque required depends on the application.
Max.

mcgyvr likes this.

Aug 27, 2009
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