Shaker power amplifier for electrodynamic vibration test systems

01

Match the amplifier kVA to the force your shaker must produce

Brüel & Kjær's system data for its V830 and V850 shakers lists the SPA-K amplifier from 8 to 32 kVA in 8 kVA increments, with a rated output of 100 V rms (sine) and 80 A rms continuous (sine and random) per 8 kVA increment, plus 240 A per increment for 100 ms as transient current. [1] The same document rates each shaker by amplifier: a V850-240 gives 7.1 kN sine force (peak) with the SPA8K and 14.2 kN with the SPA16K, and a V850-440 reaches 22.2 kN sine with the SPA32K. [1]

Editorial calculation: 100 V rms × 80 A rms = 8,000 VA, which matches the 8 kVA module step; going from SPA8K to SPA16K on the V850-240 raises sine force by 14.2 ÷ 7.1 = 2.0 times, but the same table shows the V830-185's sine force rising only from 6.8 to 8.9 kN, so ask the supplier for the force table of your exact shaker and amplifier pair rather than scaling from kVA. [1]

Brüel & Kjær's V8 system data lists the same SPA-K design from 40 to 56 kVA in 8 kVA increments for larger shakers. [2] ECON's amplifier page describes the amplifier's role the same way — amplifying the vibration controller's signal and sending it to the vibration generator — and lists its VSA-H series as all-digital IGBT amplifiers built from a standard 8 kVA power module, with a maximum instantaneous output of 3 times rated and parallel current-sharing unbalance below 1%. [3]

Give the supplier the shaker model or its armature rating, the sine, random and shock force and the displacement, velocity and acceleration you need, the payload and fixture mass, the test standards to be run, the controller in use, the mains voltage and frequency, the room cooling and ventilation, and any noise limit for the test area.

02

Check bandwidth, noise, distortion and efficiency

For the SPA-K, Brüel & Kjær lists a full-power bandwidth of 20 Hz to 3 kHz, a modulation range of dc to 10 kHz, a signal-to-noise ratio above 68 dB relative to 100 V rms output, total harmonic distortion given as a typical 0.5 to 0.8% at rated output into a rated resistive load, an input sensitivity of 1.0 V for 100 V rms output and a 10 kΩ nominal input impedance. Switching frequency is 150 kHz; efficiency is above 90%, not including the field power supply, and module efficiency is 93%. [1]

ECON lists its smaller VSA amplifiers for miniature shakers and exciters at up to 1,000 VA, 95% energy conversion efficiency and 0.1 Hz to 10,000 Hz, and its VSA-H modules with switching frequency up to 150 kHz and conversion efficiency above 95%. [3] Editorial note: the two makers state frequency range and efficiency on different bases — full-power bandwidth versus operating range, and with or without the field supply — so ask each supplier for bandwidth at rated output, the efficiency basis and the distortion measured into your shaker's load.

The system data also states what the installation must provide: an ambient working temperature of +5 to 30 °C, cabinet dimensions of 1870 × 537 × 825 mm (H × W × D), and, for a V850 system, a maximum input requirement of 26.0 kVA with the SPA8K up to 47.6 kVA with the SPA32K, including the amplifier, cooling fan and pneumatic pedestal box. [1]

03

Inside the amplifier cabinet: power modules, controls, interlocks and cooling

04

Amplifier ratings to request for a given shaker

Brüel & Kjær publishes force only for named shaker-and-amplifier pairs, so tie every value below to the shaker you will drive.

05

Tell the supplier which shaker and tests

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Shaker: [model; armature; force ratings]
Tests: [sine; random; shock; displacement]
Payload: [mass; fixture]
Amplifier: [kVA; bandwidth; noise; distortion]
Site: [mains; cooling; noise limit; floor space]
Interfaces: [controller; interlocks]

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