Re: Food processor

Bill wrote:
In article <44o3o7F34e8bU1@xxxxxxxxxxxxxx>,
"Del Cecchi" <delcecchiofthenorth@xxxxxxxxx> wrote:


If the wire in the windings is small and cheap, you can suck a lot of watts that get converted into heat and not output from the motor. And if there isn't much steel in the motor, again to save money, it might saturate and let the current shoot up and not do much useful work. Ever wonder why an immersion blender might say to only run for a minute continuous? Or why kitchen aid mixers don't want to be run too long continuously? How many of the "600 watts" of my new pro 600 go into making the motor and case hot? Gets pretty warm in about 10 min. What is the specific heat of a kitchen aid mixer?


Well, its all about being in the general ballpark with kitchen appliances, because if you are worried about 20% of performance, then you are probably engineering it too tightly. The variable nature of the material as well as the variable nature of the processes you are working with would indicate a higher factor of safety in selecting the right tool for the job.

The fact that efficiency varies according to a motor's loading and speed indicates that you are unlikely to be driving it at its most efficient point of operation anyway.

I agree with most of your points above, but a sheet detailing the details of the motor's characteristics going to be useless to almost all customers. Manufacturers may offer 'professional' models with higher use duty cycles, larger motors, or stronger construction, but even then there are no guarantees about performance. Thus customers will buy the 'standard' model or the 'professional' model and that's all they generally want to know (OK, so we know you're not an average customer).

I would agree that labelling with VA (not power) ratings for an appliance do not accurately tell the purchaser how much useful work you can get out of an appliance, but it can get you in the ballpark in comparison against other models of similar appliances. If this is really important, you should get/measure the torque/speed curves of that appliance, and match it up with the expected duty cycle for heat dissipation and then make your decisions based on that. And even then, the design of that appliance may make it less desirable than another with a lower useful power output, especially if the other appliance can make this available power achieve the end result more efficiently.

I fear that this discussion on motor efficiency is a bit like debating how many angels fit on the head of a pin.

Bill

Hardly. If one reads the Cooks Illustrated mixer test one sees quite a difference between a 5qt KA and a 5qt Hobart in performance, even though the wattage is similar. Likewise KA makes a big deal about the 300 watt vrs the 325 watt vrs the 350 watt.

So watts is not an especially useful measure. If that is what you were saying above I would agree with that. The whole small appliance spec business reminds me of cheap stereo equipment. This amp will do 500 watts peak power.

del

--
Del Cecchi
"This post is my own and doesn’t necessarily represent IBM’s positions, strategies or opinions.”
.

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