Having the correct dynamometer performance is critical to the test bed providing reliable and repeatable results. We are able to provide you with numerous permutations of dynamometers offering different technology, cost or performance benefits depending upon the project requirements.

We have a preferred group of suppliers for dynamometers to offer the best mix of performance and affordability depending upon the application. However, we are not tied to specific suppliers and can provide or integrate with your chosen supplier if you prefer.

AC Dynamometers (Asynchronous)

Sierra CP supplies transient AC dynamometers with associated regenerative inverter drives up to 1,000 kW and 8,000 Nm and 20,000rpm for numerous small and large engine and vehicle test applications.

When we review your request for a small engine dyno, our approach is most often based on a modular design to ensure that we meet technical specifications with the most cost-effective methods.

Sierra’s solutions encompass both higher-speed gasoline engine requirements, as well as the typically higher-torque demands from modern diesel engines.

Mechanical power absorbed by the dynamometer is converted into electrical energy and is then exported from the drive, typically this exported energy will be regenerated into the main electrical supply, or can be sent to a load bank and wasted as heat. Many dynamometers are air cooled.

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PM Dynamometers (Permanent Magnet)

For ultimate transient response and high speed performance we can provide you with a PM dynamometer.

They generally have a very low inertia and as such can run at higher speeds for a given power and torque.

The low inertia also enables very high acceleration rates (< 80,000rpm depending upon the model).

PM dyno’s generally need a different inverter drive specifying to traditional asynchronous AC dynos mainly to the higher switching frequencies and resultant inefficiency that causes, but these are readily available and just need correct sizing to allow for this de-rating.

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EC Dynamometers (Eddy Current)

These dynamometers only provide absorbing capability to the test piece.

Load or rotational resistance is created by a rotor operating within a magnetic flux, increase the flux and the load is increased, the resultant torque is generally measured using a load cell connected to the load arm, although an in-line torque flange can be connected.

EC dyno loading is controlled using one of our power modules and the resulting speed and torque feedback can be calculated into power output. 

Mechanical energy absorbed is converted to heat in the cooling water, this water then needs cooling by a cooling tower (open circuit) or a blast cooler (closed circuit).

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Hydraulic Dynamometers (Water brakes)

In our testing business, hydraulic dynamometers started it all over 100 years ago. They are effectively controllable water wheels and still offer immense power density. Control is by way of a high speed outlet valve and a controllable inlet valve. They have an inherent low inertia, which whilst fast responding can also lead to instability issues. Hydraulic dyno’s are a torque reaction device measuring the force using a load cell connected to a load arm which equates to a torque value. 

The mechanical energy absorbed is transferred to the cooling water by way of heat and this equates to the power being absorbed, the cooling water needs cooling either with a cooling tower (open circuit) or a blast cooler (closed circuit). 

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Other Dynamometer Configurations

It is possible to combine absorbing dynamometers with electric dynamometers, this can offer a cost effective tandem solution when one of the items already exists.

Typically the absorbing dynamometer will be used for the majority of the absorbing power with the electric drive providing some additional loading, a faster response to torque changes or motoring capability, simulating engine overrun or effects during gear changes.

Other options include using two ac dynamometers in series to provide smaller form factors and pitch centre distances. Adding starter motors or air starters to EC or Hydraulic dyno’s.

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