How fast can you turn a motor before the magnet powderizes?

In summary, the maximum rotational speed a magnet can withstand before structural failure depends on the material and bearing tolerance, with NIB magnets having a higher compressive strength than tensile strength. The mode of failure at high RPM is usually a tensile failure of the armature components, resulting in damage to the stator poles and motor lock. When a winch with a DC motor and gearbox is allowed to free-run under load without power, the rated RPM of the motor can be exceeded, causing the commutator and attached winding leads and brushes to be thrown out of the armature.
  • #1
Schtoogie
9
0
Assuming the stator and windings won't burn out, how fast can a magnet rotate before it structurally fails?
 
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  • #2
Depends on the material the magnet is made from, and also the tolerance of bearings that constrain the motion of the magnet.
 
  • #3
So, NIB magnets have a way higher compressive strength (950 MPa) than tensile strength (75 MPa). As you spin it the outer edge is under greater compressive force, while the inner edge is in greater tensile force. So how does it fail at max RPM, by breaking apart or by powderizing itself? Tension or compression? And what about shear?
 
  • #4
The mode of failure due to over-speed is usually a tensile failure of the armature components with the result that the armature components hit the stator poles and the motor locks.

If you allow a winch with a DC motor and gearbox to free-run under load without power applied, the rated RPM of the motor can be exceeded. What I have seen happen is the strips of copper commutator being thrown out of the armature taking the attached winding leads and brushes with them. It makes a mess.
 

1. How does turning a motor affect the magnet?

Turning a motor at high speeds can cause the magnet to lose its magnetic properties and become powderized. This is because the rapid movement creates heat and friction, which can weaken the magnetic field and cause the magnet to disintegrate into powder.

2. Can a motor be turned too fast?

Yes, a motor can be turned too fast, which can lead to the magnet powderizing. The speed at which this occurs depends on the strength and quality of the magnet, as well as the speed and duration of the motor's rotation.

3. What happens if the magnet powderizes?

If the magnet powderizes, it will lose its magnetic properties and will no longer be able to function as a magnet. This can cause the motor to malfunction and potentially damage other parts of the machine.

4. Is there a way to prevent the magnet from powderizing?

Yes, there are several ways to prevent the magnet from powderizing. One way is to use a higher quality and stronger magnet that can withstand higher speeds. Another way is to use materials such as ceramic or alnico magnets, which are more resistant to heat and friction. Additionally, using lubricants and cooling systems can help reduce the heat and friction that can lead to powderization.

5. What is the maximum speed a motor can be turned before the magnet powderizes?

The maximum speed a motor can be turned before the magnet powderizes varies depending on various factors such as the type and quality of the magnet, the materials used in the motor, and the duration of rotation. It is best to consult with a specialist or refer to the manufacturer's guidelines for the specific motor and magnet being used.

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