60hz to 50hz [RE-wrenches]

[Windy Dankoff, Dankoff Solar]

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Dave,

I've built and used numerous small grain mill systems. I hope this helps.

Assuming the motor is a basic induction motor, not some variable speed thing --

The motor will run faster, proportionally, at 60 Hz. A grain mill 
presents a constant torque as speed increases. So, the power load on 
the motor will increase proportionally. With 240V, the power 
potential is there to overload the motor quite effectively.  HOWEVER 
--

The ONLY thing that will damage the motor is heat, which takes time 
to accumulate.

Any way or combo of ways to reduce the torque to a safe range will be 
effective. Short runs of grinding will be safe if the overload is not 
more than about 20% above continuous duty amp rating.

A grain mill run at higher speed will heat the grain much more, 
damaging some nutritional properties. Cool grinding (usually stone) 
is promoted for that reason.

If it is belt-driven, it can be slowed down by altering ratio.

Another idea is to restrict the flow of grain into the burrs, to 
reduce the grinding load.

If the motor is thermally protected, that should assure that it will 
not burn out. If not, a thermostat can be attached to the motor case 
to give thermal protection.

If the owner puts his hand directly and tightly on the motor shell 
and can leave it there for more than 3 seconds, the motor is not too 
hot. An overheated motor will begin to smell slightly before any 
damage is done.

Conversion to 50 Hz requires first to DC, then inverter.

Windy


At 11:13 AM -0500 2/12/04, David Palumbo, Independent Power & Light wrote:
>I have a customer who purchased a high quality stainless steel grain mill
>grain recently. He was careful to make sure that the wattage (320w) was
>within his systems capabilities but he was unaware that he was buying a West
>German product that uses 50hz at 220v.
>
>He wants to know the options for operating this from his Trace SW system. I
>do not have experience with 50hz motors.
>
>Can he run this off of a t-former at 60hz 235 to 240v? Would it ruin the
>motor, as well as run faster?
>
>Is there a device that can drop Hz?
>
>He can return this grain mill, but he really likes the quality I guess and
>he wants to know if I can make it work for him.
>
>Dave

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