Motor Accelerometers: Applications & Selection

As industrial equipment becomes larger and more dependent on continuous operation, equipment reliability has become increasingly important. For large industrial motors, condition monitoring can provide valuable information about the mechanical operating condition of the machine. An accelerometer is one of the commonly used sensing devices for this purpose.

What Is an Accelerometer?

An accelerometer is a sensor used to detect changes in acceleration. In industrial motor applications, it is typically installed on or near a bearing housing, bearing support structure or end bracket to capture the dynamic mechanical response of the motor.

During operation, the rotor, bearings and other mechanical components generate dynamic movement. The accelerometer converts these mechanical movements into electrical signals that can be collected and analyzed by a monitoring system.

How Does It Work?

Common industrial accelerometers include piezoelectric and MEMS technologies.

In a piezoelectric accelerometer, mechanical acceleration causes a sensing element inside the sensor to generate an electrical signal. The signal can then be processed by a monitoring system to provide information about the mechanical operating condition of the equipment.

In simple terms:

Mechanical movement → Acceleration → Sensor signal → Data acquisition and analysis

Why Use an Accelerometer on a Motor?

The main purpose of an accelerometer is to provide information about changes in the mechanical condition of the motor.

During long-term operation, conditions such as rotor unbalance, mechanical looseness, bearing-related issues or changes in coupling condition may affect the dynamic behavior of the machine.

By continuously collecting acceleration data, users can monitor changes over time and obtain useful information for maintenance planning and early identification of abnormal conditions.

Typical applications include:

• Mechanical condition monitoring;

• Operating trend analysis;

• Early abnormal-condition detection;

• Predictive maintenance;

• Fault diagnosis and maintenance planning.

The value of an accelerometer is therefore not limited to identifying an existing problem. More importantly, it can help users identify changes in equipment condition at an earlier stage.

Which Motors Should Consider an Accelerometer?

Not every motor requires an accelerometer.

For small and non-critical motors, the cost of an online monitoring system may not be justified if an unexpected shutdown has limited consequences.

Accelerometers are more commonly considered for:

Large high-voltage motors
These motors represent significant equipment investment, and unexpected failures can result in high maintenance and downtime costs.

Motors driving critical equipment
Examples include motors used for pumps, compressors, fans, mills and other important industrial machinery.

Continuous-duty motors
Motors operating continuously or around the clock can benefit from earlier information about changes in mechanical condition.

Motors with high maintenance or downtime costs
When equipment is difficult to access, repair or replace, condition monitoring can provide additional value.

Where Is an Accelerometer Installed?

The installation location depends on the motor design and the customer's monitoring requirements.

For large motors, accelerometers are generally installed at locations that can effectively represent the mechanical condition of the machine, such as near the bearing housing or bearing support structure.

Whether the sensor is installed at the drive end (DE) or non-drive end (NDE), and whether the measurement is horizontal, vertical or axial, should be determined according to the motor design, bearing arrangement and monitoring strategy.

The installation location should therefore be selected according to the actual application rather than simply standardized for every motor.

When Should It Be Considered?

An accelerometer should be considered during the motor specification stage when:

• The motor has a high power or voltage rating;

• The motor is critical to the production process;

• The motor operates continuously;

• Unexpected downtime could cause significant losses;

• The customer has a condition monitoring system;

• The project specification requires mechanical condition monitoring;

• The motor operates under demanding or complex conditions.

For standard motors without specific monitoring requirements, an accelerometer does not necessarily need to be included as a standard accessory.

An accelerometer is an important sensing component for industrial motor condition monitoring. By converting mechanical movement into electrical signals that can be analyzed, it provides useful information for equipment condition assessment, trend analysis and maintenance planning.

For large, high-voltage, critical and continuously operating motors, considering an accelerometer during the design and specification stage can help improve equipment reliability and support a more proactive approach to maintenance.