The Nitty Gritty of Noise Suppression

Typically alternators have an unfortunate side effect: excess noise creation from ripple voltage. There is inherent noise creation in any alternator, as it switches alternating current (AC) to direct current (DC).

It’s not possible to completely suppress the alternating waveform, so you can always expect some variation in the direct current. However, a few factors can make this small ripple voltage much worse.

Ripple voltage is created many ways, potentially self-triggering or resetting modules. Or modules may be hit by unclean or fluctuating power, excessive electromagnetic interference, or they simply may misinterpret sensor readings. These problems are much more common as we’ve invested in more electronics and machinery as a society. Whatever the cause of ripple voltage, suppressing it is the key to quieter operation.

Quiet operation may be critical in many commercial and industrial alternators. Ripple voltage can also reduce performance. Reducing noise and reducing ripple voltage are one and the same. So, if top performance or noise reduction is important to you, Almott 25 AT-Series alternators are a good investment.

Isolated Ground Terminal

Almott 25AT-Series alternators have an isolated negative terminal (ground) that connects directly to the negative terminal of the battery. Typically, alternators will have a case ground where they use the mounting to the engine as the point where the alternator connects to ground. The circuit is complete as the current flows through the engine and chassis of the vehicle to the negative terminal of the battery.

As the current flows through the engine and chassis it induces a voltage into the ground.  The ground, which should be clean is far from clean.  Various vehicle components, computers, sensors, modules also share the common engine and chassis ground and their functionality. Some of these electronic components are sensitive to fluctuations in their ground reference. If the ground is too noisy these sensitive devices will malfunction.

With the Almott 25AT-Series design and isolated ground connection direct to the battery, the return current is routed away from the engine/chassis ground connection.   With this isolated ground architecture, the ground reference stays clean of any transients that will adversely affect normal operation.  In addition to keeping the ground noise down, this separate cable from the alternator to the battery reduces the losses experienced with a case ground configuration.

Filter Capacitors

While filter capacitors are optional additions to other alternators, the Almott 25AT-Series alternators include filter capacitors in their design.

Filter capacitors “filter out” voltage ripples by storing energy and releasing it consistently to make the voltage more even. You don’t have to add this feature to an Almott 25AT-Series.  

Potential Alternators

Alternators from the 25AT-Series that you can choose to reduce ripple voltage include:


Elreg Distributors has many other alternators from the 25AT-Series. If you’re not sure which best fits your needs, reach out to us. Our staff has the expertise to find you the best solution for your application. Contact us today.