Motor test bench, small motor testing systems

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Dyno Equip provides the electric vehicle motor test bench to meet the performance test of the motor and its controller system of the pure electric passenger vehicle and commercial vehicle. The motor test bench can automatically or manually test the normal performance, external characteristics, efficiency characteristics, NEDC and other tests of the motor, and can measure power, torque, speed, temperature and other parameters. Thereby, the motor performance parameters can be calculated and the correlation curve can be drawn.

Passenger vehicle motor and commercial vehicle motor test bench can complete the stall torque and locked rotor current test, temperature rise test, continuous electric working characteristic test, motor maximum speed test, motor over speed test and feed operation characteristic test. At the same time, the test bench can feed the electricity generated during the test to the company’s power grid through the frequency conversion system.

The real-time dynamic control system of the motor test bench, small motor testing systems can realize the speed and torque control through the real-time controller and simulate the actual load. The main control system can communicate with the environmental chamber, power analyzer, cooling system, EUT, etc., and realize control. The data acquisition system collects signals from torque sensors, vibration sensors, temperature sensors, pressure sensors, and other sensors, and transmits them to the main control system at a high speed. The sensor data can be displayed, saved and processed in the software interface.

High-speed and high-power motor test system

The high-speed and high-power motor test bench (test system) can be used in various high-speed motor applications such as new energy vehicle drive motors, high-speed air compressor motors and high-speed magnetic levitation motors. The installation platform can be designed according to the motor to be tested, and the end flange installation structure or the base installation structure can be selected.

Motor test bench, small motor testing systems selection specifications

The selection the dynamometer is according to the characteristic curves of the motor to be tested. The dynamometer is generally controlled by a four-quadrant inverter, and it can work as electric or power generation. The system can be equipped with high and low temperature environment chamber, battery simulator or DC bi-directional power supply, power analyzer, cooling system and other accessories.

Electric passenger vehicle motor test bench parameters (Dynamometer is air-cooled)

** Permanent magnet synchronous motor

Electric passenger vehicle motor test bench

Electric passenger vehicle motor test bench parameters (Dynamometer is water-cooled for low noise test environment)

Water-cooled dynamometer for low noise test environment

Electric commercial vehicle motor test bench parameters

Electric commercial vehicle motor test bench

Key technology description of motor test bench, small motor testing systems

System architecture of motor test bench

The real-time dynamic control system of the motor test bench, small motor testing systems can realize the speed and torque control through the real-time controller and simulate the actual load. The main control system can communicate with the environmental chamber, power analyzer, cooling system, EUT, etc., and realize control. The data acquisition system collects signals from torque sensors, vibration sensors, temperature sensors, pressure sensors, and other sensors, and transmits them to the main control system at a high speed. The sensor data can be displayed, saved and processed in the software interface.

Key technical indicators

• Torque measurement accuracy: ±0.05%FS ~ ±0.1%FS
• Pulse resolution of speed sensor: 1024ppr/ 600ppr
• Torque control accuracy: ±0.5% ~ ±1%
• Speed control accuracy: ±0.01%FS
• Dynamometer maximum vibration speed value (RSM): ≤2mm/s (independent), ≤3.5mm/s (loading)
• Temperature rise of intermediate bearing seat: ≤35℃
• Maximum vibration velocity value of intermediate bearing seat (RSM): ≤2mm/s (independent), ≤3.5mm/s (loading)
• Test motor current measurement channels: 4 channels/ 6 channels
• Test motor voltage measurement channels: 4 channels/ 6 channels
• Power analyzer measurement accuracy: ± (0.05%/ 0.1% of reading + 0.05%/ 0.1% of range)
• Sampling rate of the data acquisition system: 1kHz
• User data acquisition system channel: optional
• Temperature measurement range: -50℃ ~ 200℃
• Vibration sensor measuring range (RSM): 0 ~ 20mm/s

Major test items of motor test bench

• Power and torque characteristic test of motor with controller
• Temperature rise test of motor with controller
• Motor with controller locked-rotor test
• Motor controller control strategy development verification test
• Motor with controller maximum speed test
• Braking regenerative energy feedback test of motor with controller
• Motor external characteristic test
• Development and matching optimization test of motor and controller powertrain
• Performance test and calibration test of motor and controller powertrain
• Efficiency map test
• Accelerated response test
• Torque response test
• Endurance test of steady-state cyclic loading
• Back EMF constance and waveform
• Electromechanical time constance
• Motor response characteristic test (Note: The time resolution is required to reach the microsecond level here, which is generally used for high-speed small motor testing)

Description of key technology of motor test bench

1. High performance AC dynamometer

    

   One of the core components of the motor test bench, small motor testing systems are the dynamometer. The high-speed dynamometer has the characteristics of low moment of inertia, low vibration speed, small size, good acceleration performance and efficiency. The front and rear bearings, three-phase windings and bearing temperature of the dynamometer are monitored in real-time.

   
   

2. High dynamic real-time control system

    

   The monitoring system of the motor test bench is based on an embedded real-time controller and adopts EtherCAT/ Profinet communication to achieve high dynamic control. The system’s no-load dynamic response time can reach within 10ms, which can meet the test of complex variable conditions.

3. Convenient electrical parameter measurement system

    

   The electrical parameter measurement system uses high-precision power analyzers and current transformers which can simultaneously access torque and speed signals to measure the efficiency, current, voltage and other parameters of the motor and controller.

   

4. Precision mechanical structure

    

   The mechanical structural parts are processed by high-precision machining centers with very high machining accuracy. The shaft coaxiality is better than 0.02mm.

   
   

5. Precision high-speed bearing support

    

   • High-speed angular contact ceramic ball bearings
   • Spring preload
   • Bearing temperature rise does not exceed 35℃,
   • Vibration speed is lower than 2.5mm/s (RSM) at maximum speed
   • Grease lubrication, maintenance-free, can run continuously for 20,000 hours

6. Perfect safety protection measures

    

   • Real-time temperature monitoring of the dynamometer front and rear bearings, real-time monitoring of current and voltage, real-time monitoring of speed and torque, and real-time vibration monitoring of the front and rear ends.
   • Real-time monitoring of bearing temperature and vibration of intermediate high-speed bearing support.
   • Real-time vibration monitoring of the motor under test.
   • Safety shield closed detection to form chain protection with dynamometer.
   • The electronic control system has protection functions such as short circuit, leakage, power failure, overcurrent, and overvoltage.
   • The system software has a safety detection function. When the monitoring value exceeds the threshold, it will immediately alarm. The system has three levels of protection.
   • For the durability test, the system automatically predicts the trend based on the monitored historical data such as vibration. When the prediction fails, the system will prompt user to pay attention.

   
   

7. Easy installation

    

   The L mounting bracket of the motor test bench is designed with a positioning stop and a positioning mounting surface. Through the transitional mounting flange connection connected with the test motor, the test motor can be quickly installed without centering adjustment. The L-shaped mounting bracket is designed with an interface with the high and low temperature environment chamber, and the test motor can be placed in the high and low temperature environment chamber for testing.

   Vibration sensors are installed in the X/ Y/ Z directions of the L-shaped installation tooling to monitor the vibration status of the motor under test in real time. The interface with the environmental chamber adopts four-pillar cantilever support, which can ensure that the axis of the test motor can be coaxial with the shaft system of the test bench when the high and low temperature environment changes.

   For small high-speed motors, the dynamometer can be adjusted in the axial position, and the mounting platform of the motor under test can be adjusted in the vertical direction to adapt to the motors to be tested of different sizes.

   
   

8. Complete monitoring software

    

   The motor test bench software adopts a modular design architecture. User can customize the test process and working condition parameters to realize the motor speed and torque control. The system classifies users and opens different functional modules. The system has the function of automatic zero-point calibration at start-up. The software has a dedicated sensor calibration module, and user can calibrate the sensor regularly. The communication interface with EUT is reserved to realize the control of EUT. The software has the following functions:

   • • Speed control
     • Torque control
     • Temperature monitoring
     • Speed monitoring
     • Security function
     • The standard communication interface with the host computer software
     • The limit monitoring of the DUT and the test bench can be performed to ensure that the speed of the DUT and abnormal conditions can be restored to a safe state in a very short time.
     • Open loop and closed loop control of speed and torque
     • System interface
       • Communication control interface with environmental warehouse
       • Communication control interface with cooling system
       • Communication control interface with battery simulator
       • Communication control interface with inverter
       • Communication control interface with INCA calibration system
       • Four channels CAN bus which can communicate with the test piece
       • One channel Ethernet communication interface
       • Provision the corresponding cable
     • Road simulation

    

   The vehicle road simulation function is integrated in the real-time controller. The whole vehicle road simulation function is used to realize the road resistance, slope resistance simulation and inertia simulation of the whole vehicle on the test bench. These resistance simulations can be expressed by the following formula:

   The system can provide various series of dynamometer electromechanical inertia simulation and simulate the road load according to the equation:

   RL = F0 + F1VX + F2Vn + I dv/dt + mg * (Grad/100)

   Among them:

   RL	Road load (road traction)
   F0, F1, F2, n	Road load model coefficient
   F0	Friction coefficient independent of speed
   F1	Friction coefficient related to speed
   F2	Drag coefficient
   n	F2 speed index variable (range: 1.2—3.0)
   x	F1 speed index variable (range: 0.8-1.2) (if any)
   V	Drum surface linear speed
   I	Electric simulated inertia
   dv/dt	Acceleration
   m	Mass
   g	Gravity
   grad	Slope

   The parameters F0, F1, F2, n, and x (if any) form the road load model, and they can be obtained in a variety of methods.

    

9. Shaft alignment measures

    

   For high-speed shafting, we need to ensure that the coaxiality of the shafting is not greater than 0.02mm. Generally, the following measures are taken:

   • Laser alignment tool alignment
   • With fine-tuning mechanical structure

10. Treatment measures for shafting dynamic balance

     

    The shaft system dynamic balance accuracy of the high-speed motor test bench reaches G1 and it is dynamically balanced on site. The general treatment measures are as follows:

    • The flange on the shaft system is designed with uniform threaded holes for counterweight
    • Using on-site Dynamic balance instrument for dynamic balancing

Small motor testing systems

The needs of test rig for small motor testing: Development of new drive systems for electric and high efficiency engines requires test technology that can meet the most stringent standards of serviceability and flexibility. In modern vehicles there are many electric motor. Traditionally these were limited to windshield wiper, window lift, fuel pump, sunroof, electric seat, air compressors, and lift gate or trunk latch release. With the advent of electric cars, coolant pump and refrigerant compressors have been added to the list.

Additionally, electric motor has infiltrated safety sensitive applications such as electronic throttle control, electric steering, electric door opening, cam phaser and traction motor. While all vehicle components must undergo rigorous testing, safety items must undergo more stringent durability and end-of-line testing. A number of methods can be used to physically load the motors, however, motor test rig, small motor testing systems are preferred for their high speed, flexibility and ability to back drive the test item while at high speed.

While the small motor testing systems are applying loads and temperature cycling, many data parameters are logged, some at high speed. Typical attributes are motor voltage, current, temperature, torque and speed. One area of primary interest is motor cogging (torque ripple), particularly at low speeds. Audible noise and vibration may also be a concern and sensors and data acquisition may be included for this as well.

There are many reasons to perform motor testing. Durability testing ensures that the motor will last a calculated length of time that simulates an extended life of an automobile. Performance testing is required to benchmark the motor’s performance at various temperatures and loads. Regardless of the testing type, various loads are applied while thermally cycling the motors.

Simpler motor is typically subjected to different loads but kept at relatively constant speed, with just the input voltage changed to simulate high and low battery conditions. Motor in applications such as electric steering and traction motor are subjected to very different torque and speeds.

High-speed small motor test system

The small high-speed motor test bench (test system) is used to test low-power high-speed motors, mainly for the low-power aviation generators, robot motors, small high-speed compressor motors, machine tool spindle motors, etc. The installation platform can be designed according to the motor to be tested, and the end flange installation structure or the base installation structure can be selected.

Small motor testing systems selection specifications

According to the characteristic curve of the motor to be tested, select a dynamometer. The dynamometer is generally controlled by a four-quadrant inverter and can work as electric or power generation. The system can be equipped with high and low temperature environment chamber, battery simulator or DC bidirectional power supply, low power adjustable DC power supply, power analyzer, cooling system and other accessories. According to user noise requirements, water-cooled dynamometer or air-cooled dynamometer can be selected.

Parameter table of air-cooled dynamometer for small motor testing systems

Parameter table of water-cooled dynamometer for small motor testing systems

Motor test rig, small motor testing systems technology

The scope of motor test rig, small motor testing systems comprise mechanical components such as drive test setups with torque sensor, dynamometer with torque and speed measurement and manual or external control, as well as computer controlled complete solutions for the analysis and documentation of electrical machinery.

By means of an integrated power analyzer, computer controlled dynamometers can be realized with up to 12-channel current and voltage measurement, so that a separate efficiency specification of motor and converter can be effected even for converter fed drive systems.

Motor test rig, small motor testing systems control software

The motor test rig, small motor testing systems control software serves for parameter assignment of the test stand including the converter for the active brake and the test sequences of the test system, so that an optimum of profitability and precision is achieved.

• Various test modules
• Manual operation
• Motor characteristics curve (dynamic, stepwise)
• Locked motor torque test
• Friction loss measurement
• Warm-up operation
• Static operation
• No load
• Families of characteristics curve
• Harmonic values
• Load cycles and cyclical load
• Step changes in load with transient data collection
• Load and start-up characteristics
• Recorder
• Customer specific applications
• Laboratory report

Environmental chamber as option

Electric motor laboratory and performance must include features to control the application of stimuli, the most difficult usually being temperature cycling. Many of the systems are designed to be wheeled into an environmental chamber, and if needed shield any of the sensitive test rig components from temperature extremes or humidity.

If the system is very intricate it may be necessary to replace the environmental chamber door with part of the test apparatus so that the small motor testing systems can be pushed on wheels and mated to the chamber. It is usually best not to build the test fixture rig into the chamber for serviceability reasons, but this is sometimes required for cleanliness reasons if the electric motor is part of a hydraulic pump system. External thermal generator systems are also sometimes used and a small custom thermal enclosure is built around the test item.

About dynamometer hyperlink..

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