Imitating a negator spring with an electric motor.

[ssbill]

Hi,
I need help in designing a system that would imitate a negator spring cable reel(like shown on the linked video below) but using an electric motor instead of a mechanical spring. I need it to work in order to keep a constant spring tension on a steel cable in a winch type application. Any help would be greatly appreciated especially on the ideal electric motor type/configuration. Thanks

Link

 

[waross]

Buy a constant torque motor.
Some cable reels come with a constant torque motor as standard.
You don't have to redesign the wheel, such motors are "One the shelf".
A design tip.
Don't confuse reel torque with motor torque.
We did an installation where the reel was chain driven by the constant torque motor at about a 4:1 ratio.
One designer calculated the motor torque required.
Between there and purchasing, the number was applied to the reel torque instead of the motor torque.
The reel had only 1/4 of the required torque.
The dragging cable did some incidental damage before a replacement motor was purchased and installed.

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Ohm's law
Not just a good idea;
It's the LAW!