Brief introduction of electric dynamometer:

Electric dynamometers are widely used in engine and motor performance and durability testing. In the test, the dynamometer is mainly used to implement load on the output shaft of the engine or the motor under test, so as to perform the performance test of the engine and the motor.

The electric dynamometer can realize constant speed control and constant torque control to realize a load system that applies load to the engine or motor under test and absorbs its power. At the same time, it is equipped with a display control system to test various types of vehicle engines (car engines, motorcycle engines). , General machinery engines, non-road machinery engines, etc.), motors (such as: single three-phase asynchronous motors, synchronous motors, DC motors, series motors, power tools, hub motors, starters, automotive motors, etc.) output torque, Speed, power and characteristic curve. The system configuration test module can test the engine's temperature, pressure, flow and other parameters during engine testing, and the system configuration related test module can test the motor's voltage, current, power, and temperature parameters during motor testing. According to the working principle of the dynamometer, it is mainly divided into hysteresis dynamometer, magnetic particle dynamometer, electric turbine dynamometer, and electric dynamometer.

Especially for the power dynamometer system, the DC motor or AC variable frequency motor is used as the main component to convert electrical energy into the braking mechanical energy of the motor rotor, and load the motor or motor under test in the form of torque. The load torque is controlled to realize the simulation of the mechanical load carried by the engine or electric motor.

Dynamometer system composition diagram

Electric dynamometer is a comprehensive test equipment for performance testing of various power machinery. It is mainly used to test the input power of fans, water pumps, hydraulic or gear transmissions, and can also be used to test the output power of engines. Function (with electric working conditions and power generation working conditions), high-performance important testing equipment. It is coaxially connected with the motor under test through a shaft connector, and is used to simulate and control the load of the motor under test to measure the torque, speed, current, voltage, power, efficiency and other parameters of the motor. And other special dynamic test items, such as safety test, dynamic balance test and so on.

　Application case of PFA rectifier feedback device in dynamometer industry

Analysis of the current dynamometer control system scheme:

The first option:

Use ABB, Siemens frequency conversion feedback integrated machine (four-quadrant frequency converter) to meet the operational requirements of the dynamometer. This kind of scheme has high price, good torque accuracy and stable speed accuracy.

The second option:

Use ABB, Siemens ordinary vector frequency converter to match the PFA rectification feedback device scheme, to meet the dynamometer operation requirements. This kind of scheme, on the one hand, integrates the general advantages of ABB and Siemens inverter vector algorithms, and the torque accuracy and constant speed accuracy fully meet the accuracy requirements of the dynamometer. On the other hand, the use of PFA rectifier feedback device is more cost-effective, and it can stably feed back the energy of the test motor in the power generation state to the grid, current harmonics <5%, voltage harmonics <1%.

The third option:

For domestic four-quadrant inverters, the price of this type of program is not much different from that of the second program, but the vector algorithm of domestic inverters is limited, especially in terms of speed stability accuracy and torque accuracy control that affect the performance of the dynamometer.

PFA rectifier feedback device core technology description:

⑴ Adopt high-speed DSP central processing unit:

Upgrade a new generation of rectifier feedback control software, with accurate control accuracy, good stability, less harmonics, and strong anti-interference ability;

⑵ Adopt the latest SVPWM modulation technology in the industry:

Upgrade the new generation of SVPWM vector control technology to meet the current harmonic requirements of the national standard for rectification and feedback;

⑶ Standard RS485 communication and power feedback display:

The product is equipped with standard RS485 communication and keyboard communication display, and all software control parameters are open for display and debugging, which is convenient for product monitoring;

⑷ Prevent islanding effect:

The software monitors the status of the power grid in real time, and the power outage of the power grid will immediately stop the power feedback to the grid to prevent the islanding effect;

⑸ Using LC filter technology:

Optimize LC filter, effectively suppress harmonics and electromagnetic interference, voltage and current THD<5%, to ensure clean energy feedback;

⑹ Using phase sequence automatic discrimination technology:

Upgrade the automatic phase sequence identification technology, the phase sequence of the three-phase power grid can be connected at will, no need to distinguish the phase sequence artificially;

⑺ Upgrade the hardware design to exceed the requirements of the national standard withstand voltage:

The newly upgraded hardware design meets the withstand voltage of 2500V AC for 1min, and the leakage current is less than 2mA, which is far lower than the national standard 30mA requirement;

⑻ Improve the rectifier feedback current level of the machine:

The newly upgraded hardware and control software reduce the volume of the product by more than 31%, and at the same time, increase the current by 34%;

⑼ Configure fuse:

Equipped with DC and three-phase AC fuses, short-circuit protection is in place to ensure the safe operation of the inverter;

⑽ Built-in input filter device, full noise filtering, the interference to the power grid is 1/4 of the ordinary commercial inverter;

⑾ Built-in rectifier feedback active front end, which can feed regenerative energy back to the grid. The built-in reactor and filter can be directly connected to the grid, and the energy feedback efficiency is as high as 97%. Compared with general-purpose inverters, it can save energy by 20%-50%, and its heat loss is less than 3% of resistance braking, which reduces heat sources and increases safety factor;

⑿ Built-in rectifier feedback active front end, using IGBT rectification, compared with the general inverter rectifier bridge rectification, the grid capacity can be reduced by 15% to 25%;

⒀ Built-in rectifier feedback active front end, power factor up to 0.99;

⒁ Built-in rectifier feedback active front end, during rated operation, the grid voltage distortion THD<5%, the grid current distortion THD<5%, meeting the power grid quality requirements;

⒂ All-around full-drive, compatible with permanent magnet synchronous motors and asynchronous motor controllers;

⒃ 485 communication function, supporting 485 mainstream communication protocol in RTU mode;

⒄ With multiple protection functions such as overcurrent, overload, short circuit, overvoltage, hardware overvoltage, undervoltage, grid phase loss, grid amplitude, overheating, external fault input, etc., to ensure safer and more reliable system operation;

⒅ Simple installation, debugging, operation and convenient maintenance;

Application case analysis of dynamometer rectification feedback device:

Tianjin Keda Power Testing Technology Co., Ltd. is mainly engaged in the testing of motorcycles, automobiles, engines and their key components. It has a development history of more than 20 years. It has been using Siemens general vector inverters and our PFA rectifiers since 2008. Solutions for feedback devices.

Take the ACD-11 AC power dynamometer, which is a special testing equipment for the bench test frame of a small general gasoline engine as an example. The system adopts AC motors and frequency conversion control technology, as well as computer technology and test software to meet the test requirements of small general gasoline engines. .

1. Use on-site pictures:

Tianjin Keda 37KW Dynamometer Control Cabinet

2. Main functions:

1. This system is mainly composed of the following parts:

(1) Host: AC power dynamometer;

(2) Dynamometer control: SIEMENS AC frequency conversion speed regulation device, using manual knob to adjust operating conditions;

(3) Detection and data processing part: Industrial computer is used to detect and display various detection parameters, perform data management, print test reports, and draw engine characteristic curves;

2. Using SIEMENS full digital control device, AC electric dynamometer has two operating states: electric and dynamometer. The engine can be driven to make the engine run automatically when it is electric, and load is applied to the engine when dynamometer. The control characteristic is fast and stable;

3. When the dynamometer is running, the mechanical energy of the engine is fed back to the power grid by the PFA rectifier feedback device. It can reach the rated torque capacity of the dynamometer when it runs below the rated speed of the variable frequency motor of the dynamometer, and can reach the rated torque of the dynamometer when it runs above the rated speed of the variable frequency motor of the dynamometer The rated power of the dynamometer;

4. The dynamometer adopts constant speed control or constant torque control mode;

The system test accuracy maintains the control accuracy of Siemens general vector inverter

(1) Speed: ±0.2% ±1r/min;

(2) Torque: ±1%;

Technical specifications of PFA rectifier feedback device