The Modern Test Software: imc OMEGA

The imc OMEGA software platform is the integration software for all imc e-motor test stands. It was developed in-house by imc and is being continuously developed further.

imc OMEGA consists of two part:

1. Basic software
2. Modular test types

As a result of basic, standardized software with a fixed range of functions, the user interface of all imc test stands is the same. This minimizes the training required and allows all customers to benefit from the further development of our basic software.

Functionality at a Glance:

  • Comfortable and user-friendly interface for configuring and performing tests
  • Software is available in German and English – other languages on request
  • Test procedures can be adapted easily to different motors and procedure scenarios
  • New test types of your own can be created without programming knowledge
  • Customers can develop their own program code for test sequences, control loops,  and automation according to need
  • Feedback control loops can run on an imc measurement system with realtime capabilities in clock cycles of < 1 ms
  • Automatic evaluation of measurement data after the test has been completed
  • Results can be documented as a PDF protocol
  • Measurement data can be exported into third-party formats such as MS Excel, Matlab, and many more
  • Analysis interfaces for the data analysis software imc FAMOS for in-depth evaluation
  • User administration with a multilevel user rights system

Basic Software

The basic software provides general functions for test administration and test parameters. It monitors the critical threshold values to protect test objects and controls the data storage for recorded measurements and calculated test results. It also contains password controlled user administration, which controls user access to the various fields and manages user rights.

Manual Control

The test stand allows for monitored manual control. Via input instruments on the user interface, the operator can adjust test stand process quantities and perform manual testing such as, for example, switching on supply voltage individually, release of the test object or load machine, and specifying RPM or maximum torque. According to input, measurement data acquisition and communication with the test stand, the periphery test object or controller of the test object continue to run in the background. The threshold values of the test stand are monitored and, if exceeded, an error message is issued, testing is discontinued and the test stand placed in a safe state.

Test Plans

Test plans allow cyclical test repetition and cascading of predefined tests. This allows the test object to be subjected to a whole series of tests that do not need to be explicitly started one after another by an operator. Such sequences can therefore run, for instance, overnight, over the weekend or over a longer period of time (endurance tests).

Test Types

The imc OMEGA test software offers a variety of modular test types. These can be selected modularly depending on the test tasks and motor types. The following descriptions are therefore abstractly independent of the motor types.

For a better overview, the test types can be divided into the following categories:

  1. Loadless test types
    These are test types that do not require any external load from a load unit.
     
  2. Passive test types
    These are test types in which the test object is not energized.
     
  3. Active test types
    These are test types in which the test object is energized.
     
  4. Customized test types
    In addition to the test types described above, there are a large number of test types that are defined customer-specifically and reflect the special features of the area of application of the test item.

Load-free Test Types

Test types that can be conducted without a load unit, operating the DUT in idle mode without external load beyond its own inherent inertia, are termed load-free test types. These include:

Parameter identification EC

The Parameter-Identification method is a turnkey, model-based procedure for determining the characteristic parameters of an electronically commutated permanent electromotor.

Description of test procedure

The DUT is placed in its mounting in accommodation to the physical test mechanism and electrically connected. Once the safety mechanisms have been locked, the motor is energized or braked, in order to produce a dynamic change of rotation speed. During the process of energizing, the DUT’s value limits are monitored in order to prevent it from becoming overloaded. After conclusion of the test, the DUT’s primary descriptive parameters, as well as derivative parameters, are calculated. Subsequently, the DUT is released so that it can be removed or discharged from the mounting.

Primary results of test type

  • resistance
  • electric excitation
  • inductance
  • dynamic friction
  • static friction
  • inertia

Exemplary derived results of the test type

  • no-load speed
  • no-load current
  • starting current
  • blocking torque
  • electrical time constant
  • mechanical time constant
  • RPM-constant
  • torque constant

Fluxtable EC dynamic

The dynamic flux table measurement determines the magnetic flux in the d and q direction as a function of the impressed total current. For this purpose, the test specimen is dynamically loaded and measured the resulting load points. In addition, the ohmic losses as well as the friction and iron losses of the test object are recorded..

Description of test procedure

For dynamic flux table measurement, the DUT is connected to the inverter. At the beginning of the test, the winding resistances of the test object are determined in a DC current supply. The test specimen is then accelerated to the test speed and then dynamically accelerated and decelerated by various current presets in the d and q directions. For each individual current step, the current angle is also varied step by step.

At the end of the test, the friction torque is measured again in a downward ramp and the winding resistance is determined in a DC current supply. With the aid of these measured data, the influence of the moment of inertia in the speed ramps is compensated, as well as the heating of the windings during the test

Exemplary derived results of the test type

  • Magnetic flow in d-direction as a function of d- and q-current
  • Magnetic flow in q-direction as a function of d and q current
  • Internal electrical torque
  • Maximum torque for given current and voltage limits as a function of speed
  • d-current depending from the speed to generate the optimal torque curve
  • q-current as a function of the speed to produce the optimal torque characteristic
  • d-current as a function of the speed and torque for the minimum total current at the operating point
  • q-current as a function of the speed and torque for the minimum total current at the operating point
  • total current as a function of the speed and torque at a minimum total current at the operating point
  • Electrically absorbed power as a function of the speed and torque with minimum total current in the work
  • Mechanically delivered power as a function of speed and torque with minimum total current at operating point
  • Efficiency as a function of speed and torque with minimum total current at operating point
  • Ohmic losses as a function of the speed and torque with a minimum total current at the operating point
  • Friction losses as a function of the speed and torque
  • Total losses as a function of the speed and torque with a minimum total current at the operating point

Parameter Identification DC

The Parameter-Identification method is a turnkey, model-based procedure for determining the characteristic parameters of a brush-commutated permanent DC motor.

Description of test procedure

The DUT is placed in its mounting in accommodation to the physical test mechanism and electrically connected. Once the safety mechanisms have been locked, the motor is energized or braked, in order to produce a dynamic change of rotation speed. During the process of energizing, the DUT’s value limits are monitored in order to prevent it from becoming overloaded. After conclusion of the test, the DUT’s primary descriptive parameters, as well as derivative parameters, are calculated. Subsequently, the DUT is released so that it can be removed or discharged from the mounting.

Primary results of test type

  • terminal resistance
  • generator constant
  • inductivity
  • dynamic friction
  • static friction
  • inertia

Exemplary derived results of the test type

  • no-load speed
  • no-load current
  • starting current
  • blocking torque
  • electrical time constant
  • Mechanical Time constant
  • Speed constant
  • torque constant

Passive Test Types

Passive test types is a term used for those types in which the test object is mechanically connected to a driving machine and is not energized itself.

Back EMF

When permanent magnet motors are actuated externally, they induce a voltage which can be measured at the machine’s connection terminals. The induced voltage is proportional to the rotation speed and the excitation. During this test, the DUT is not powered.

The plot of the induced voltage provides information on the windings and on the extent of the excitation over the circumference. Measurement of the induced voltage represents a simple method to diagnose the DUT’s electromagnetic characteristics.

Exemplary derived results of the test type

With this type of test, the relevant measured variables of the induced motor voltages and the angle of rotation of the motor axis are recorded. After evaluating the test, the motor voltages can be displayed over the angle of rotation and the order spectrum of the motor voltages. In addition, the harmonic distortion is calculated for all motor voltages.

With the help of this information, the deviation of the motor voltage from the desired curve can be assessed.

  Electric motor testing back EMF

Cogging Torque

In electrical motors, the motor’s internal structure causes cogging torques. These occur when the motor rotates and can be measured at a slow rotation speed. During this test, the DUT not powered. The measured plot of the torque provides information on the DUT’s internal structure. Measurement of the torque represents a simple method to diagnose the DUT’s electromagnetic characteristics.

Description of test procedure

The DUT is connected with the test stand’s load machine via a coupling. Once the test starts, the load machine drags the DUT for a specified time towards a target speed. The load machine holds this target rotation speed constant for the duration of the data acquisition. After conclusion of data acquisition, the load machine brakes the DUT’s motion down to a standstill.

Results of test type

  • time plot of measured torque
  • plot of torque over rotation angle
  • order spectrum of measured torque

What do I see in the report?

  • Cogging Torque over the mechanical angle (CW and CCW)
  • Order spectrum of the cogging torque
  • (With experience and knowledge of the structure of the engine, individual orders can be assigned to specific engine components)
  • mean friction torque over one revolution
  • Peak-to-peak value of the cogging torque

  Electric motor testing cogging torque

Torque to Drive

The drag torque test determines the loss torque of a passively towed DUT as a function of the speed. Here, the average moment over a mechanical revolution is always considered. The torque fluctuation within one revolution can be determined by a cogging torque test.

The drag torque is usually determined mainly by the bearing friction. But also other loss moments, such as Eddy current torques in a permanently excited motor or the air friction of a firmly connected fan wheel are included in the measurement result. In addition, the mass moment of inertia of the test object (plus coupling and measurement side of the measuring shaft) can be determined with the drag torque test.

Description of test procedure

To measure the drag torque, the electrically non-contacted test object is dragged by the load machine with the specified gradient to a defined speed (nprüf) and then brought to a standstill again with the same gradient. The test is carried out one after the other in both the positive and negative direction of rotation.

Exemplary derived results of the test type

  • Time course of the drag torque
  • Time course of the speed
  • Drag torque over the speed
  • Static Friction
  • Sliding Friction
  • Inertia

What do I see in the report?

  • Drag torque over speed
  • Table with individual working points
  • Motor parameters:
    • Static friction,
    • speed-proportional friction,
    • inertia,

  Electric motor testing torque to drive

Encoder Test

The encoder test serves to assess the quality of the device encoder. For this purpose, the angle signal output by the device under test is compared with that of a reference encoder. In addition, the angle signal of the DUT encoder is displayed in relation to the generator voltage of the motor.

Description of test procedure

The contacted test object is towed by the load machine to a constant speed, see figure. When the setpoint speed is reached, both the terminal voltages of the DUT and the angle signal of the encoder and the reference encoder signal are recorded during the test time.

Exemplary derived results of the test type

  • Deviation of the encoder angle to the reference winding above the reference angle
  • Angle signal above the reference angle
  • Regenerative terminal voltages of the test object above the reference angle

  Electric motor testing encoder test

Active Test Types

Active test types is a term used for test types in which the test object is mechanically connected to a load machine and energized.

Characteristic curve EC dynamic speed controlled

The characteristic curve test is used to determine the average behavior of the powered motor over one revolution as a function of the speed. This means that the motor can be characterized in its capacity as a converter from electrical to mechanical energy. For this purpose, currents, voltages and torque are recorded as a function of the speed and from this the electrically consumed power, the mechanically output power and the efficiency are determined. The determined characteristic curves depend on the control of the motor, in particular on the specification of the d and q currents over the speed. The characteristic curve test can be used to determine the performance that can be achieved with a specific control strategy in order to provide a starting point for further optimization.

The dynamic characteristic curve test measures the entire speed range of a test object in a short time. This minimizes the heating of the motor. If measurements are to be made in the thermally steady state or if the control speed of the test object current controller is insufficient, a static characteristic curve test is the better choice.

The test can only be used for current-controlled test objects. If the device under test cannot be operated in this mode, the torque-controlled characteristic test must be used.

Description of test procedure

At the beginning of the test, the test item is dragged by the load machine with the gradient to the starting speed and then the current is switched on. During a parameterizable waiting time, the test item swings in so that a stationary torque is set on the shaft. After this waiting time, the speed of the load machine is increased linearly from the steady start speed to the stop speed. After the stop speed has been reached, the device under test first waits for it to settle. The load machine then drives the test item to the starting speed again while it is switched on. This double ramp approach allows the torque characteristic to be corrected by the proportion of the moment of inertia. If the starting speed is reached again, the test object current is switched off. After a further settling time, the load machine brings the test object to a standstill by following a linear ramp with the gradient. After the end of the test, the load machine drags the passive test object over an upward and downward ramp. This is used to determine the commutation angle for the evaluation of the characteristic travel.

Exemplary derived results of the test type

  • Torque curve over speed
  • Current curve over speed
  • Voltage curve over speed
  • Efficiency over speed
  • Input power versus speed
  • Output power versus speed
  • Current curve over the speed in the d-axis
  • Current curve over the speed in the q-axis
  • Voltage curve over speed in the d-axis
  • Voltage curve over speed in the q-axis

What do I see in the report?

  • Torque versus speed
  • RMS current / voltage over speed
  • d / q current versus speed
  • Motor input / output power via speed
  • Efficiency over speed
  • Table with working points

  Electric motor testing characteristic curve EC dynamic speed controlled

Characteristic curve EC static speed controlled

The characteristic curve test determines the average behavior of the motor over one revolution as a function of the speed. The focus is on characterizing the properties of the motor as a converter from electrical to mechanical energy. For this purpose, currents, voltages and torque are measured as a function of the speed and thus the electrical power consumed, the mechanical power output and the efficiency are determined. The determined characteristic curves are always dependent on the control of the motor, in particular on the specification of d and q current versus speed. The characteristic check determines the performance of the control strategy and is the starting point for further optimization in the control algorithm.

The static characteristic test measures the behavior of the motor at various specified constant speeds. Measurements are made over a time interval that starts when the desired speed is reached and the motor current has stabilized. Compared to the dynamic characteristic curve test, in which the entire speed range is measured, the static method can only make statements about the measured speeds, but these are usually more precise. Above all, the dynamics of the test object current regulator have a significantly lower influence here.

 

Description of test procedure

The load machine drags the active test item to the first speed n1. After a settling process, there is a stationary moment on the measuring shaft and the measuring time is started. This process is repeated for the other speeds n2 to n8 after the measuring time has elapsed. The test current and current angle for the individual speeds, which lead to a maximum torque, can be taken from the measurement data of the flow table measurement for the individual speeds.

Exemplary derived results of the test type

  • Torque curve over speed
  • Current curve over speed
  • Voltage curve over speed
  • Course of the efficiency over the speed
  • Course of the electrical input power over the speed
  • Course of the mechanical output power over the speed
  • Current curve over the speed in the d-axis
  • Current curve over speed in the q-axis
  • Voltage curve over speed in the d-axis
  • Voltage curve over speed in the q-axis

  Electric Motor Testing Characteristic curve EC static speed controlled

Torque ripple

Due to their electromagnetically asymmetrical structure, the torque on electro motors fluctuates over a single revolution. This torque ripple amounts to a problem in various applications, for instance in electrically assisted steering in the automotive industry.

By measuring the torque ripple at a fixed rotation speed and a specified torque value, it is possible to obtain information on a motor’s behavior in the target application. In this test, the DUT is actively powered and the test procedure can be parameterized individually.

Description of test procedure

The DUT is connected with the test stand’s load machine via a coupling. Once the test starts, the load machine drags the DUT for a specified time towards a target speed value. Once the system’s transient states have subsided, the DUT is powered up and a steady-state torque on the shaft emerges. The DUT’s controller then regulates the shaft torque to the specified value. The rotation angle and shaft torque are recorded over a specified time duration. Once this time elapses, the shaft torque is regulated down to zero and the load machine runs the DUT down to a standstill.

Exemplary derived results of the test type

  • time plot of resulting shaft torque
  • time plot of rotation angle
  • plot of shaft torque over rotation angle
  • order analysis of torque ripple

  Electric Motor Testing Torque ripple

Phase Resistance

The resistance measurement determines resistances of the 3 windings of a three-phase motor. By comparing the measured resistances can be seen on the one hand how evenly the windings are performed. On the other hand, deviations from the expected resistance may indicate winding errors, e.g. a wrong winding number or insulation fault. Finally, the winding resistance can also be deduced from the winding temperature.

Description of test procedure

In the resistance measurement, a constant measuring current is impressed into the test object in three different configurations in order to determine the three string resistances independently of one another. The following procedure has proven useful:

  • Measuring current from terminal 1 to terminal 2, terminal 3 almost de-energized
  • Measuring current from terminal 2 to terminal 3, terminal 1 almost de-energized
  • Measuring current from terminal 3 to terminal 1, terminal 2 almost de-energized

Exemplary derived results of the test type

  • Motor winding resistances

  Electric Motor Testing Phase Resistance

Inductance

The inductance measurement is used to measure the winding inductance of a motor. In this case, the change in inductance over a mechanical revolution and thus the dependence on the rotor position is detected.

Description of test procedure

First, a DC current is impressed through two terminals of the DUT to measure the terminal resistance of the motor. Subsequently, a sinusoidal alternating current is impressed on the same two terminals and the test specimen is slowly rotated by the load machine, so that the terminal inductance can be absorbed above the angle of rotation. At the end of the test, the terminal resistance is measured again.

Exemplary derived results of the test type

  • Inductance over the revolution of the motor

  Electric Motor Testing Inductance

Flux table static

The flux table measurement serves to determine the magnetic flux in d- and q-direction as a function of the impressed total current. For this purpose, the test specimen is measured in static load points. In addition, the ohmic losses, as well as the friction and iron losses of the test specimen are recorded.

With the help of the obtained information, an optimal control of the motor can be calculated as a function of the speed. That is, it can be calculated for each predetermined speed, and current and voltage limit of the total current and current angle that meet a certain torque request with minimal current effective value. This automatically minimizes ohmic losses and maximizes the efficiency of the entire drive system.

Test procedure description

For static flow table measurement, the DUT is connected to the inverter. At the beginning of the test, the winding resistances of the test object are determined in a DC current supply. The test specimen is then towed by the load machine to the test speed. Here, the friction torque of the test specimen is measured as a function of the speed. Now the DUT is energized in several operating points. The amount of (total) current is gradually increased. In addition, the current angle is varied step by step for each individual current step. There are adjustable cooling pauses between the individual energisations.

At the end of the test, the friction torque is measured again in a downward ramp and the winding resistance determined in a DC current supply. With the aid of these measurement data, the influence of the moment of inertia in the speed ramps is compensated, as well as the heating of the windings during the test.

Results of the test

  • Magnetic flow in d-direction as a function of d- and q-current
  • Magnetic flow in q-direction as a function of d and q current
  • Internal electrical torque
  • Maximum torque for given current and voltage limits as a function of speed
  • d-current depending from the speed to generate the optimal torque curve
  • q-current as a function of the speed to produce the optimal torque characteristic
  • d-current as a function of the speed and torque for the minimum total current at the operating point
  • q-current as a function of the speed and torque for the minimum total current at the operating point
  • total current as a function of the speed and torque at a minimum total current at the operating point
  • Electrically absorbed power as a function of the speed and torque with minimum total current in the work
  • Mechanically delivered power as a function of speed and torque with minimum total current at operating point
  • Efficiency as a function of speed and torque with minimum total current at operating point
  • Ohmic losses as a function of the speed and torque with a minimum total current at the operating point
  • Friction losses as a function of the speed and torque
  • Total losses as a function of the speed and torque with a minimum total current at the operating point

  Electric motor testing flux table static

Special Test Types

Structure-borne Noise / Vibration

In structure-borne noise tests the signals of one or more piezoelectric sensors are recorded in high resolution. Evaluation is carried out according to customer specifications.

imc Test & Measurement is an Axiometrix Solutions company.