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bbq_build
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Hello, I need to measure the moment of inertia of a DC motor's rotor. Any suggestion? Thanks
RogueOne said:What kind of relevant measurement tools do you have access to? Do you have a motoring dyno?
There is always this concept available as well
I would be inclined to just use a string and a weight. Wrap the string around the shaft some number of times and use a stopwatch to measure how long it takes for the weight to fall through some distance. Use the diameter of the shaft and the mass of the weight in your calculations to get to the MOI. Sounds like a fun project...bbq_build said:Thanks. I don't have a motoring dyno. I am trying to measure the inertia at home without fancy equipment.
berkeman said:I would be inclined to just use a string and a weight. Wrap the string around the shaft some number of times and use a stopwatch to measure how long it takes for the weight to fall through some distance. Use the diameter of the shaft and the mass of the weight in your calculations to get to the MOI. Sounds like a fun project...
Similiar to the Chuck on an electric drill; usually does not require a key to tighten.bbq_build said:Anybody knows what Collet is?
Sirsh said:There is a way you can measure MMoI of irregular geometry by attaching it to a spring (say a steel rod) about its centre and then measuring the period. From that you can find the Inertia using fundamental vibration analysis.
fN = 1/T = 1/(2*pi)* sqrt(k_theta/I)
Natural frequency or period, T, can be measured. K_theta of the steel connecting rod is GJ/L. Substitute into equation above and you will get an approximation of the Inertia.
Sirsh said:There is a way you can measure MMoI of irregular geometry by attaching it to a spring (say a steel rod) about its centre and then measuring the period. From that you can find the Inertia using fundamental vibration analysis.
fN = 1/T = 1/(2*pi)* sqrt(k_theta/I)
Natural frequency or period, T, can be measured. K_theta of the steel connecting rod is GJ/L. Substitute into equation above and you will get an approximation of the Inertia.
bbq_build said:Thanks. What is l, GJ and L? How do I find those values?
The moment of inertia of a motor's rotor can be calculated by using the formula I = mr^2, where m is the mass of the rotor and r is the distance of the mass from the axis of rotation. This can also be calculated by using specialized equipment such as a torsion pendulum or a flywheel.
The moment of inertia of a motor's rotor is an important parameter in determining the motor's performance. It affects the motor's start-up and stopping time, as well as its overall stability and efficiency. Measuring the moment of inertia can also help in the design and optimization of the motor.
The units of moment of inertia are kilogram square meters (kgm^2) in the SI system of units. In the imperial system, it is expressed in pound square feet (lbft^2). It is also sometimes measured in terms of mass moment of inertia, which has units of kilogram square meters per second (kgm^2/s).
Yes, the moment of inertia of a motor's rotor can change depending on factors such as the distribution of mass, the speed of rotation, and the position of the axis of rotation. It can also be changed intentionally by adding or removing mass from the rotor.
Yes, it is important to follow proper safety precautions when measuring the moment of inertia of a motor's rotor. This can include wearing protective gear, ensuring the equipment is stable and secure, and following the manufacturer's instructions carefully. It is also important to double check all measurements and calculations to ensure accuracy.