# What is inertia in DC motor?

## What is inertia in DC motor?

What is a simple definition for “moment of inertia,” often described as inertia in a motor? Inertia describes the tendency of a body to resist changes in rotational speed for a given torque. For a ratio of 1:1 the necessary torque during acceleration is equally applied to the load and the motor.

### What is load inertia for motor?

Load inertia, or moment of inertia, is the resistance of any physical object to any change in its speed from the perspective of the rotational axis.

#### What does high inertia mean?

Higher moments of inertia indicate that more force has to be applied in order to cause a rotation whereas lower moments of inertia means that only low forces are necessary. Masses that are further away form the axis of rotation have the greatest moment of inertia.

Is low inertia good?

A common rule of thumb is to strive for an inertia ratio of 10:1 or less. A higher ratio increases system response time and resonance, causing the system to overshoot the target velocity and position. Large inertia mismatches also require the motor to draw more current, making the system less efficient and more costly.

In terms of motor starting, a high inertia load is one that requires a relatively lengthy acceleration period before the motor achieves normal operating speed. High inertia loads are found in motor starter applications throughout industry.

## What is torque to inertia ratio?

Defined as the motor’s holding torque divided by the inertia of its rotor. The higher the ratio, the higher a motor’s maximum acceleration capability will be.

### Is a higher moment of inertia better?

#### Does inertia increase with speed?

For both interpretations, the answer is ‘yes’ since force still acts in an opposite force on anything which has mass. As you accelerate, your velocity increases and therefore mass will increase. The increase in mass will bring about an opposite force. The greater the mass, the greater the inertia.

What is the effect of high inertia loads on induction motor?

The alternative rating applied to induction motors, is the maximum load inertia. This is the maximum load inertia that can be started by this motor. A higher inertia would result in to much rotor heating and premature rotor failure.

Where can I find the inertia of a motor?

Inertia of a motor can be found in the manufacturer’s datasheets. However, the overall system inertia depends on the mechanical configuration of the system. Hence, motor inertia given by the manufacturer cannot be treated as the system inertia. Accurate system inertia estimation is crucial for controller modeling.

## How to calculate the moment of inertia ( J )?

Plot the two points and draw a straight line. Using the formula: edit: The stall torque is given in the data sheet. Measure the no-load speed. Plot the two points and draw a line. Maybe the calculated number will be approximately correct. See if the motor manufacturer will provide a value.

### How is motor inertia related to resonance problems?

Increasing the ratio of motor inertia to load inertia is one of the most reliable ways to improve resonance problems. This is because the smaller the ratio of load inertia to motor inertia, the less compliance will affect the system.

#### Which is the peak speed of motor inertia?

A polynomial speed profile is required. The selection process starts with the determination of the peak load speed and acceleration, using equation Eq. (2.27), the maximum speed occurs at t = 0.375 s and maximum acceleration occurs at t = 0 s. The peak motor speed required is 800 rev min −1.