What does
"Speed at rated load" mean?
Metabo WE 15-150
No-load speed 9600 RPM
Speed at rated load 9600 RPM
Metabo W 13-150
No-load speed 10,000 RPM
Speed at rated load 7000 RPM
It’s the amperage rating you should pay attention to in addition to the other specs.
I don’t know whether a different motor is used, or different gearing, but the motor that “doesn’t slow down under load”, is basically a higher amperage rated motor, that runs at a slower speed than it is capable of.
The lower speed is caused by electronics that keep the speed lower.
When a load is applied, the power to the motor increases, keeping the speed constant.
This is usually a feature found on European “industrial rated” tool models, typically with other features, such as automatic motor shut off if power temporarily cuts, overload protection, and sometimes, but not always, variable speed adjustment.
Years ago, Flex Tools (The German power tool brand), used to be owned by Porter Cable.
The Flex branded tools were sold in the USA as “Flex by Porter Cable”, and typically had the “Tacho Constamatic (TC) Full-wave Electronics” with the other features I mentioned, but not necessarily the variable speed.
Grinders that looked basically identical, except body color and labels, that were also made in Germany, were sold under the Porter Cable brand and colors, but without the “fancy” electronic modules.
The Porter Cable branded/colored models cost half what the Flex branded tools cost.
At the time, a lot of users preferred to avoid the fancier models, both due to cost, but also because the electronic modules didn’t always work well with alternative power sources, like generators, but also because one of the most likely components to fail in tools with the fancy electronic modules is the fancy electronic module, and for European made tools, the replacement parts were usually expensive.
In the case of that Metabo, the electronic unit is about $62, so I wouldn’t worry about it so much, and the feature is nice in use.
