Unholtz Dickie Corp
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Energy Saver Replacement Power Amplifiers

Replacement Amplifiers for Shaker SystemsUnholtz-Dickie offers a full line of high-performance Class D switching power amplifiers. These amplifiers, used in UD’s new shaker systems, are offered as replacements for older, water-cooled vacuum tube amplifiers or bipolar transistor amplifiers.

Many vibration test systems purchased more than 20 years ago include low-efficiency, water-cooled power amplifiers housed in large multi-bay consoles. These old technology linear amplifiers consume large amounts of 3-phase electrical power, occupy excessive amounts of valuable floor space and require environmentally “unfriendly” water cooling systems. All of these problems have one common solution: a new SA Series Power Amplifier from Unholtz-Dickie!

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Key benefits include:

  • Energy Saver design
  • IGBT Technology
  • Totally air-cooled
  • Modular layout from 15 to 720 KVA 
  • Class D, high-efficiency switching design: >90% efficiency
  • EMI shielded cabinet
  • Small footprint with up to 120 KVA per bay
  • Increased shock performance
  • Safety interlocks for operator & system protection
  • NO transformer coupling
  • SA-Command Link for remote operation from APEX SL
  • Very low maintenance

SA Series

The SA Series Power Amplifiers have become a benchmark in class D power amplifier design for electrodynamic shakers. Representing the latest technology in IGBT circuit design, these amplifiers provide one of the most efficient totally air-cooled designs in the industry. These compact amplifiers are modular in design, and can be configured from 15 KVA up to 720 KVA in one to six bay consoles.

UD's newest SA Amplifiers offer even more efficiency and performace than the old MOSFET and early IGBT base amplifiers. SA Series Amplifiers include a comprehensive operating/status meter panel for push-button startup and monitoring of critical amplifier/shaker status, voltages and currents. A simple push-button selection provides for external startup through a simple contact closure. In addition, all SA Series Power Amplifiers can be configured with the new SA-Command Link Interface which allows communication with the APEX SL Vibration Control System for starting, stopping and monitoring the amplifier/shaker system.

Advanced designs in filtering and shielding have provided significant improvements in the reduction of radiated and transmitted emissions (EMI). The standard SA Series power amplifiers are provided with a special EMI shielded console designed with minimal penetrations including metal gaskets on all external joints, special plating for better electrical continuity and corrosion protection, EMI shielded cooling ducts, and 3-phase line filtering.

Elimination of Water Cooling

SA Series power amplifiers are 100% air-cooled, eliminating cooling water consumption and the related expenses associated with maintaining cooling towers (chillers), pumps and leaky pipes/hoses.

Reduced Power Consumption

Energy Saver SA Series power amplifiers are over 90% efficient and typically use less than half the 480V (380V) 3-phase power that existing linear power amplifiers consume for the same test. Further power savings are achieved due to the reduced load on the cooling tower (or chiller) which previously had a combined load from the shaker and power amplifier. A typical 20,000 lbs force vibration system with an old technology linear amplifier rejects about 170 KW to the cooling water loop at maximum force output. After replacing the original linear amplifier with an air cooled SA Series Amplifier, the total system heat rejected to the cooling water loop is only 50% of the original load. This results in major savings at the cooling water tower (chiller). Conversely, this extra 85 KW of cooling capacity could be used for other lab equipment.

Up to 720KVA in a single amplifier!

Reduced Floor Space

A typical water cooled linear amplifier rated at 120 KVA output is housed in a 5 or 6 bay console, occupying approximately 30 sq. ft. of actual floor space plus another 25 sq. ft. for required wall clearance. The Model SA120 (120 KVA) is housed in a 1-bay console (5 sq. ft. plus wall clearance). This floor space advantage speaks for itself.

Increased Random and Shock Performance

The SA Series amplifiers typically provide at least 10% more random vibration performance and 50% more shock performance than a comparable linear amplifier. Contact UD for the performance characteristics on your specific shaker/amplifier combination.

Spare Parts and Service Support

Some amplifier suppliers have officially discontinued parts and service support for their water-cooled linear amplifiers, thereby forcing their customers to find a replacement solution. SA Series power amplifiers are available to replace most brands of linear amplifiers (see table below). Please contact UD for a recommendation and prompt quotation for your system.

SA Series Power Amplifiers can be used to upgrade older UD shaker systems (including Models from the 200 Series, 500 Series and RTS Series, in addition to the T1000, T4000 and T5000 Models), as well as those from other manufacturers.


  • Final KVA requirements are based on the shaker efficiency, manufacturer and age.
  • Force ratings are estimates based on typical input KVA ratings. Actual force values will depend on shaker efficiency, manufacturer and age.
  • Estimated force rating based on sine and random testing. Shock performance will be higher.

UD Energy Saver Replacement Power Amplifiers have been interfaced to a variety of shakers from different manufacturers. Typical large, older competitor systems were supplied with messy hydrostatic bearing oil supplies, large heat exchangers, and massive matching transformers. UD SA Series Amplifiers are DIRECT COUPLED, eliminating the need for the transformer. In addition, the neatly packaged shaker heat exchangers and oil supplies will reduce floor space by up to 80%! A partial listing of competitive shakers that can be easily driven by SA Amplifiers includes:

Shaker Models
860 C60 249
890 C90 300
964 C150 335
984 C210 340
994 C220