Specific guide for technical file for converter electrical motors

Specific additional guide for preparation of technical file for electrical motors with Converter

The requirements of this guide are added to “Guideline for preparation product technical file for ATEX certification” (I-O-20)

Note: A converter is also known by other terms. For example, a frequency converter, a converter drive, an inverter drive, a variable speed drive, an adjustable speed drive (ASD), or a variable frequency drive (VFD).

Marking

Motors that are started and operated with a converter must:

Include the phrase 'For Converter Operation' on a label which should be attached to them.
Indicate the range of speed and operating frequency of the motor.
Indicate the application and torque specifications.

For example: variable torque, constant torque, constant power, etc.

If a specific type of converter is required, its specifications must be indicated.

Instruction

The following items, in addition to other necessary standard requirements, must be included in the manual for this type of motors:

A speed/torque diagram.
For the motors with Exe protection, that have been type-tested with a converter, the converter specifications should be mentioned for comparison and selection of the appropriate converter by the user (usually presented in a table format)
- Rated motor current

Weighted Voltage Total Harmonic Distortion (WTHD), or pulse frequency
DC-Link voltage

Protections provided for motor operation by the converter (if any)

Risk assessment

The parameters and information required for the use of the converter must be stated in the technical file and equipment manual (according to IEC 60079-0:2018, clause 24 and clause 30).

The Ex protections provided by the converter must be explained.
High-frequency switching in converters can cause stress on the windings and cables, which can create a source of ignition.
This condition, as well as an assessment of the risk and relevant necessary precautions (such as the use of a filter at the output of the converter), must be evaluated.
Stray currents can occur as a result of converter operation. Some effective ways to reduce the risk include:
- Using an appropriate filter between the converter and motor.
- Using shaft earthing or bonding brushes with suitable protection for the intended EPL.
- Using insulation techniques for the shaft and bearings.
- A proper earthing system to equalize the potential of the components.
- Using symmetrically configured low-voltage cables for the connection between the converter and motor.
- Using a converter with appropriate topology that matches the motor design to minimize common mode voltage.
- Other methods to reduce common mode voltage and stray currents.

Temperature evaluation and measurement

In general, for most equipment under testing, the maximum surface temperature should be measured at a voltage between 90% to 100% of the rated voltage, at the level that results the highest surface temperature increasing.

For electric motors

The same instruction applies to electric motors. However, as an alternative, the testing can be conducted at the worst-case voltage (the voltage that results the highest temperature increasing) within the voltage range of Zone A according to IEC 60034-1, which is usually within the range of ±5% (indicating a note in the Special condition of use).

For motors powered by a converter

For motors that operate with a converter (with variable power and speed), it is necessary to create the thermal performance of the motor with the converter (and the output filter, if used) across the entire specified speed and torque range. This process can be carried out through calculations and testing.

The evaluation and testing should be performed in accordance with the conditions outlined in Annex E of the IEC 60079-0:2018.

For these motors, voltage variations are applied to the input of the converter, not directly to the motor. Therefore, the worst-case temperature increase should be measured by varying the voltage at the input of the converter.

ATEX guides

Specific guide for technical file for converter electrical motors

ATEX guides

Specific additional guide for preparation of technical file for electrical motors with Converter

The requirements of this guide are added to “Guideline for preparation product technical file for ATEX certification” (I-O-20)

Note: A converter is also known by other terms. For example, a frequency converter, a converter drive, an inverter drive, a variable speed drive, an adjustable speed drive (ASD), or a variable frequency drive (VFD).

Marking

Motors that are started and operated with a converter must:

Include the phrase 'For Converter Operation' on a label which should be attached to them.

Indicate the range of speed and operating frequency of the motor.

Indicate the application and torque specifications.

For example: variable torque, constant torque, constant power, etc.

If a specific type of converter is required, its specifications must be indicated.

Instruction

The following items, in addition to other necessary standard requirements, must be included in the manual for this type of motors:

A speed/torque diagram.

For the motors with Exe protection, that have been type-tested with a converter, the converter specifications should be mentioned for comparison and selection of the appropriate converter by the user (usually presented in a table format)

Rated motor current

Weighted Voltage Total Harmonic Distortion (WTHD), or pulse frequency

DC-Link voltage

Protections provided for motor operation by the converter (if any)

Risk assessment

The parameters and information required for the use of the converter must be stated in the technical file and equipment manual (according to IEC 60079-0:2018, clause 24 and clause 30).

The Ex protections provided by the converter must be explained.

High-frequency switching in converters can cause stress on the windings and cables, which can create a source of ignition.

This condition, as well as an assessment of the risk and relevant necessary precautions (such as the use of a filter at the output of the converter), must be evaluated.

Stray currents can occur as a result of converter operation. Some effective ways to reduce the risk include:

Using an appropriate filter between the converter and motor.

Using shaft earthing or bonding brushes with suitable protection for the intended EPL.

Using insulation techniques for the shaft and bearings.

A proper earthing system to equalize the potential of the components.

Using symmetrically configured low-voltage cables for the connection between the converter and motor.

Using a converter with appropriate topology that matches the motor design to minimize common mode voltage.

Other methods to reduce common mode voltage and stray currents.

Temperature evaluation and measurement

In general, for most equipment under testing, the maximum surface temperature should be measured at a voltage between 90% to 100% of the rated voltage, at the level that results the highest surface temperature increasing.

For electric motors

For motors powered by a converter

The evaluation and testing should be performed in accordance with the conditions outlined in Annex E of the IEC 60079-0:2018.

For these motors, voltage variations are applied to the input of the converter, not directly to the motor. Therefore, the worst-case temperature increase should be measured by varying the voltage at the input of the converter.