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 25 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 SC Series Power Amplifier from Unholtz-Dickie!

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Key benefits of power switching amplifiers include:

  • Energy Saver design
  • Ultra-rugged, reliable Silicon Carbide (SiC) MOSFET Technology
  • Totally air-cooled
  • Modular layout from 20 to 725 KVA 
  • Class D, high-efficiency switching design: >90% efficiency
  • EMI shielded cabinet
  • Small footprint with up to 125 KVA per bay
  • Increased shock performance
  • Safety interlocks for operator & system protection
  • NO transformer coupling
  • SA-Command Link for remote operation from an APEX Series Vibration Controller
  • Very low maintenance

SC Series

Unholtz-Dickie Power Amplifiers have become a benchmark in class D power amplifier design for electrodynamic shakers. Representing the latest technology in Silicon Carbide (SiC) MOSFET 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 20 KVA up to 725 KVA in one to six bay consoles.

Use of proven, ultra-rugged Silicon Carbide (SiC) MOSFET's offers even more efficiency and performance than the older MOSFET and IGBT based amplifiers.  This major enhancement has allowed UD amplifiers to achieve up to 25% higher peak current than amplifiers using IGBT's, a major boost for both Random and Shock testing.  All UD SC 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 SC Series Power Amplifiers can be configured with the new SA-Command Link Interface which allows communication with an APEX Series 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 SC 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

SC 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 SC 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 SC125 (125 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 SC 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. SC 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.

SC 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 SC 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 SC Amplifiers includes:

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