AC dynamometer working principle, AC dyno


Common applications for AC dynamometer (transient electric AC dyno) includes high speed and general purpose applications, automotive, aircraft or aerospace, chain or belt drives, gearboxes, fluid power systems, gas or diesel engines, industrial, marine, transmissions and turbines. AC dynamometer (transient electric AC dyno) or high speed dynamometer typically has speed and power feedback for performance testing and monitoring. Typical features include encoders or other speed or position sensors, torque arms and various types of sensors. AC dynamometer interface includes integrated console, independent console, computer, etc.

The general functions of AC dynamometer include PID control, data acquisition or recording, alarms, power analysis and engine exhaust analysis. The transient electric AC dyno, including air cooled and water cooled dynamometer, are well suited for any types of development and function tests of engine, transmission, powertrain, high speed e-drive and e-motor using in plug-in hybrid, range extender or pure electric vehicles. The test bench application ranges from simple steady state operation up to sophisticated tests with transient and dynamic test cycles.



Advantages of AC dynamometer (transient electric AC dyno)


  • The AC dynamometer can be operated in four quadrants, either as generating or as motoring. It can be loaded clockwise or anti-clockwise.
  • Energy saving and environmental protection. Significant energy-saving effect can make mechanical energy convert into electrical energy and feedback to the grid.
  • The load characteristics are very good. The constant torque load can be maintained within the rated speed, even under blocked or reversed rotation. This is particularly suitable for small torque testing. The constant power load can be maintained above the rated speed.
  • The transient electric AC dyno can have constant torque (loading) or constant speed (generating mode) two working methods to adapt the different test requirements.
  • Constant torque and constant speed load control stability is much better than other loading methods. It maintains extremely high stability at full speed range (even at zero speed) and torque.
  • Alarm protections such as overload, overspeed, overvoltage, overcurrent, overheat, phase loss, fluctuations, etc.



Three phase AC dynamometer possess the following features


  • Minimal maintenance and therefore increasing test bench availability
  • Small space requirement due to compact design
  • Steady state and dynamic test condition due to integrated accurate torque measurement flange
  • High speed dynamometer up to speed of 25,000 rpm with low vibration and noise level
  • Special end-shield design with integrated cooling circuit bringing high AC dynamometer stiffness
  • High dynamic testing due to low rotor moments of inertia

Air cooled AC dynamometer for highly dynamic test


The air cooled AC dynamometer (transient electric AC dyno) with state-of-the-art and future-oriented technology can satisfy present and future test demands for engine and automotive components. The low moment of inertia and high overload capacity together with speed gradients can guarantee highly dynamic response. The power ranges represent the torque characteristics of electric machines, modern gasoline and diesel engines for passenger cars and commercial vehicles using in conventional, hybrid or electrified applications. The torque sensor can be mounted on AC dynamometer.

Another high torque series of transient electric AC dyno makes these loadings optimally cover the power ranges of medium-size and heavy-duty of diesel engines or electric machines used in commercial vehicle and as output of powertrain and transmission test. This AC dynamometer series provides the dynamic response required for sophisticated simulation tasks.



High power, high torque with high speed dynamometer

ModelRated power (kW)Rated torque (Nm)Rated speed (rpm)Max. speed (rpm)


Air cooled high speed dynamometer

ModelRated power (kW)Rated torque (Nm)Rated speed (rpm)Max. speed (rpm)

** Permanent magnet synchronous motor

Water with air cooled AC dynamometer for higher power and torque


This AC dynamometer (transient electric AC dyno) takes part of a new cooling concept, the stator is water cooled while the end windings of the dynamometer are air cooled, resulting in reduced noise level. Two individual fans ensure effective cooling of the end windings and the rotor. The stiffer body of this transient electric AC dyno series can reduce vibration and guarantee a safe and trouble free operational process. This AC dynamometer has a more compact design with more power and torque for achieving higher dynamics.



ModelRated power (kW)Rated torque (Nm)Rated speed (rpm)Max. speed (rpm)

Water cooled AC dynamometer for noise and heat control


This AC dynamometer (transient electric AC dyno) series is cooled by water with very low noise level. Another advantage is the thorough area intensive cooling by the direct heat dissipation over cooling water. This high quality and robust transient electric AC dyno series has the long wearing insulated bearings for minimal maintenance. The AC dynamometer with associated components are tested under extreme conditions.



ModelRated power (kW)Rated torque (Nm)Rated speed (rpm)Max. speed (rpm)

** Shaft height: 132mm

Compact size AC dynamometer for transmission test


In the field of automotive testing system, the AC dynamometer (transient electric AC dyno) features include compactness, small diameter, low inertia, high power, high torque, high response and low noise. In the case of hybrid transmission test benches, for example, it is possible to drive the test bench by AC machine for higher efficiency and energy saving instead driving by an actual engine.

For this purpose, however, it is necessary to have a small diameter construction to avoid interference with the transmission and attain the characteristics of low inertia and high response to reproduce an engine pulsation torque. Also in the engine test cell, the use of a high response and low inertia transient electric AC dyno is indispensable when building a dynamic load test bench for simulating vehicle’s driving conditions.

To cope with such needs of the times, the low-inertia AC dynamometer (transient electric AC dyno) series is developed. Besides, for the e-motor reducer test bench with one drive dyno and two output dynamometers, due to the large size of output AC dyno and the narrow distance between input shaft and output shaft of reducer (transmission), there is no much space to fit the drive dyno.

There are two conventional installation methods. One is to add an extra gearbox for increasing distance between input shaft and output shaft. Another method is to install the input shaft with an angle for increasing installation space of drive dynamometer.


Model**Rated power (kW)Rated torque (Nm)Rated speed (rpm)Max. speed (rpm)

** Shaft height: 132mm


Conventional transmission test bench using an extra gearbox increasing distance between transmission input and output shafts


Conventional transmission test bench with an angle-mounted for increasing installation space of input dynamometer


The correct reducer or transmission test bench layout


For new generation powertrain development requirements, customer testing requires ultra-compact and extremely powerful AC dynamometer (transient electric AC dyno). Comparing with standard dynamometer, the power density of DynoEquip dynamometer is greatly improved. The secret of success lies in the special and patented cooling system. The cooling element is integrated in the stator lamination. The main advantage is that its heat loss can be absorbed directly in the position where it occurs.

Comparing with standard dynamometer, this new transient electric AC dyno does not have any double steel pipe. The advantage is that the weight and mounting dimensions can be significantly reduced. Other advantages are the minimum vibration value and the lowest noise level.

Ultra high speed dynamometer for aviation or aerospace test


The ultra high speed permanent magnet synchronous AC dynamometer (transient electric AC dyno) offers by DynoEquip is robust, almost maintenance free and variable speed. The transient electric AC dyno construction consists of a cast housing and two end-shields with integrated mounting feet. Water cooling is the standard design. This AC dynamometer series is used for electrical vehicle motor testing and applications related to aviation and aerospace.

The AC dynamometer performance can be tailored as customer request. The oil-air lubrication or grease replenishing technology is deployed. The adapter can be fabricated according to customer demand.


ModelRated power (kW)Rated torque (Nm)Rated speed (rpm)Max. speed (rpm)

Motor torque calculator, calculation online


This motor torque calculator, calculation online provides a fast and easy way to calculate speed, torque or power in SI unit (kW, Nm) or Imperial unit (HP, lb-ft) which helps for dynamometer or motor design and calculation works. The conversions are automatically and accurately generated.


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