Wilcoxon WST7B3 User manual

Wilcoxon Sensing Technologies

8435 Progress Drive, Frederick MD 21701, USA

Amphenol (Maryland), Inc d/b/a Wilcoxon Sensing Technologies

Tel: +1 (301) 330-8811

Tel: +1 800 WILCOXON

Fax: +1 (301) 330-8873

www.wilcoxon.com

97042 Rev A 11/21

WST7B3power amplifier

Operating guide

97042 Rev A 11/21 Page 2 of 16

Contents

Safety section 3

Safety summary 4

1.0 Product description 5

1.1 Front panel 5

1.2 Rear panel 7

2.0 Operation of the power amplifier 8

2.1 Using the power amplifier with an electromagnetic shaker 8

2.2 Using the power amplifier with a piezoelectric shaker 9

2.3 Matching networks 9

3.0 Initial system setup 11

3.1 AC line power 11

3.2 Signal input 11

3.3 The power amplifier, matching network, and shaker cables 11

4.0 Operation 12

4.1 Connecting to AC power 12

4.2 Test operation 14

5.0 Maintenance 15

6.0 Technical assistance 16

6.1 Technical assistance 16

6.2 Customer service 16

97042 Rev A 11/21 Page 3 of 16

WARNING: OPERATION OF THIS AMPLIFIER IS SAFE WHEN THE INSTRUCTIONS IN THIS

MANUAL ARE READ THOROUGHLY BEFORE THIS SYSTEM IS CONNECTED TO ELECTRICAL

POWER. PARTICULAR ATTENTION MUST BE PAID TO THE SAFETY SECTION OF THIS

MANUAL. IT IS THE ULTIMATE RESPONSIBILITY OF THE USER TO SAFELY SET UP,

OPERATE AND MAINTAIN THE SYSTEM.

WARNING: TO PREVENT FIRE OR SHOCK HAZARD, DO NOT EXPOSE THIS EQUIPMENT TO

RAIN OR MOISTURE.

WARNING: LETHAL VOLTAGES ARE PRESENT IN THE AMPLIFIER AND MATCHING

NETWORKS. THE AMPLIFIER CONTAINS ENERGY STORING DEVICES. THEY MUST BE

ALLOWED TO DISSIPATE ENERGY BEFORE OPENING THE AMPLIFIER ENCLOSURE.

Safety section

The power amplifier can be safely operated when the instructions in this manual are carefully followed.

This section summarizes the safety considerations. Reminders, in the form described below, will

appear in the detailed instructions to assure operator awareness of these safety considerations.

Qualified personnel should operate and maintain this power amplifier only after becoming thoroughly

familiar with this manual.

WARNING: This symbol is used in the instruction manual where operator safety must be

considered. The instruction manual should be consulted and read carefully.

CAUTION: This symbol is used when caution is needed to prevent damage to equipment.

It is used where careful attention to certain procedures described in the instruction manual

is needed. This symbol is also used to emphasize procedures other than normaloperating procedures.

97042 Rev A 11/21 Page 4 of 16

Safety summary

1. Make sure that the power amplifier is properly grounded to a good earth ground.

2. Make sure that any piezoelectric shaker being driven is properly grounded to a good earth ground.

3. Disconnect the power cord at its source before connecting or removing power amplifier cables.

4. To reduce the risk of electric shock, do not remove the power amplifier cover. No user-serviceable

parts are inside. Refer all servicing issues to Wilcoxon Sensing Technologies.

5. Do not attempt to operate a power amplifier without the protective covers secured.

6. All cables must be connected between the power amplifier, matching network and shaker before

electrical power is connected. Inspect for frayed or cut cables prior to operation.

7. Hearing protection devices are highly recommended in the vicinity of a piezoelectric shaker

whenever the shaker is being driven at high output levels.

8. Do not expose this equipment to rain or moisture.

9. Lethal high voltage may be present at the power amplifier output connector.

10. Use common sense and avoid haste!

97042 Rev A 11/21 Page 5 of 16

1.0 Product description

The WST7B3is a single-channel, rack-mountable power amplifier designed to high performance

standards. The WST7B3develops a maximum of 900 watts of power into a 4 Ohm load. The amplifier

will drive the full range of Wilcoxon shakers, with the ability to drive the larger shakers to the full

performance limits of the shakers.

The WST7B3combines the latest power amplifier technology with uniquely simple circuit technology to

reduce distortion of all types, and at all power levels, over the full frequency range. In addition to

performance achievements, the power amplifier is designed for long-term reliability and exceptional

resistance to abusive operating conditions.

The power amplifier has circuit breaker protection for AC power input.

Specifications WST7B3

Power output 900 Watts, maximum, into 4load

Power bandwidth 0.5 Hz to 100,000 Hz

Input sensitivity 2.5 Volt peak, for full output

Input impedance 10 k, nominal

Dimensions 19” wide, 15.5” deep, 5.25” high

Weight 42 lb

Power requirements 115V, 15A (WST7B3) or 220V, 15A (WST7B3-220)

1.1 Front panel

1.1.1 Power switch: The front panel features a push-on/push-off type latching power switch used to

apply or remove AC line power to the SoftStart circuitry. Note that the rear circuit breaker must be on

for the amplifier to power-up.

97042 Rev A 11/21 Page 6 of 16

1.1.2 Power indicator: The WST7B3has an LED indicator above the power switch to monitor the

following conditions:

POWER UP SEQUENCE –After pushing the power switch, the LED will turn from unlit to red

(mute). When the power supply has stabilized, the amplifier will come out of mute and the LED

will change to green (normal operation).

UNLIT LED (No power) –The amplifier channel LED when unlit indicates no AC mains power is

present at the channel power transformer. This usually indicates that the amplifier probably

needs only to be powered on.

CLIPPING (flashing red) –Clipping occurs when the amplifier output level no longer can follow

the level increase at the input (over driven input condition). When a channel is driven into

clipping, the channel LED will change from green to red then back to green when the level is

reduced. Momentary clipping can be tolerated, however, it indicates that maximum undistorted

power has been surpassed and potential speaker/shaker damage may result if overload

conditions persist. Any amplifier that is constantly operaed into clipping indicates a more

powerful amplifier is neededfor that application.

THERMAL SHUTDOWN (orange) –The amplifier has thermal shutdown circuitry to prevent

damage due to overheating. Should thermal shutdown occur, the channel will mute, and the

channel LED will turn orange. When the channel has cooled to a safe operating condition, the

channel will return to normal operation.

97042 Rev A 11/21 Page 7 of 16

1.2 Rear Panel

1.2.1 Connecting to AC power: Please check the Data Plate on the right rear of the amplifier to verify

power requirements agree with your location. Before plugging in the power cord, make sure the Mast

Circuit Breaker is switched to the “ON”position. Plug the IEC-320 C14 end of the power cord into the

amplifier, then plug the other end into an approved and grounded AC receptacle. The “STATUS”LED

should flash green, then switch to red, indicating AC power is present in the unit.

1.2.2 Master Circuit Breaker: The WST7B3amplifier uses a magnetic-trip

circuit breaker to protect the amplifier. This breaker is not an on/off switch

and must be in the “ON”position during the installation and normal

operation. Use the front panel push-button power switch or an external control

voltage to power-up or power-down the amplifier.

Should the breaker trip, or switch “OFF,”lower or remove the amplifier input signals. Remove the AC

power by disconnecting the power cord from the amplifier for 20 seconds. Switch the breaker to the

“ON”position. Reconnect the power cord, then power the unit up normally. The circuit breaker must be

“ON”at all times for the WST7B3amplifier to operate.

1.2.3 Output connector: Connection to the shaker or matching network is accomplished by attaching

high quality cable to the Output Binding Posts. The output binding posts provide three different

interconnect options:

BANANA PLUGS (Optional) provide a quick disconnect option. Before inserting a banana plug

into the binding post, be sure to tighten the post nut to avoid rattling and to provide full insertion

of the banana plug.

SPADE LUGS (Recommended) provide high contact area and secure fastening. Post diameter

is 5/16”(8mm), lug width 5/8”(16mm).

STRIPPED BARE WIRE (Not Recommended) up to 3 gauge can be inserted through the hole in

the binding post and held in place by tightening the post knob. Additional tightening pressure

97042 Rev A 11/21 Page 8 of 16

can be achieved using a coin in the slots of the knob.

1.2.4 Input connector: Single-ended BNC and Balanced XLR and TRS connections are available and

can be selected using the Input Select switch on the rear panel of the amplifier. It is recommended to

use the BNC single-ended input. The balanced input requires a balanced pre-amplifier source.

1.2.5External/local switch: To power-up the amplifier using an external control voltage, supply a 5V

to 12V AC or DC control voltage to the ‘IN’ terminals of the control voltage connector. Use paired wire

of 22 to 18 gauge between the source device and the WST7B3amplifier. By selecting the switch to the

“external” position, the amplifier will power-up only when the control voltage is present (on). Immediately

following power up, the control voltage will appear at the ’OUT’ terminals of the control voltage

connector for the control of other equipment. The removal of the control voltage (0V) causes the

amplifier to turn ‘off’ and the control voltage at the ‘OUT’ terminals will be interrupted. In the “Local”

setting, the amplifier will ignore the control voltage and power up only by using the front panel push-

button power switch. If a control voltage is present at the ‘IN’ terminals, it will still be available at the

‘OUT’ terminals after the power-up sequence.

Notes: The “OUT”terminals are connect to the “IN”terminals once the amplifier has powered-up. The

control current is determined by the source equipment. The carrying current of the “OUT”relay is 2

Amps. The amplifier’s control circuitry itself draws less than 2mA from the control current when

operating.

2.0 Operation of the power amplifier

Wilcoxon Sensing Technologies manufactures a comprehensive line of vibration generating systems,

including electromagnetic and piezoelectric shakers. Electromagnetic shakers are powered directly

from the output of the power amplifier. However, piezoelectric shakers require a matching network

between the power amplifier and the shaker. A signal source to drive the power amplifier is not part of

the system and must be supplied by the user. This guide describes the operation of the WST7B3power

amplifier. Other guides describe the operation of the matching networks and shakers. For all vibration

97042 Rev A 11/21 Page 9 of 16

generating systems a customer supplied signal generator is necessary to operate the vibration

generating system. A piezoelectric accelerometer to monitor vibration output is strongly recommended.

2.1 Using the power amplifier with an electromagnetic shaker (models F3, F4, F10)

There are no specific requirements for the WST7B3amplifier to connect with the aforementioned

electromagnetic shakers.

2.2 Using the power amplifier with a piezoelectric shaker (models F7 and F7-1)

The power amplifier will drive piezoelectric shakers but must have a matching network between the

power amplifier and the shaker for full output.

CAUTION: In these modes of operation power amplifier must be used with a Wilcoxon

matching network. Do not attempt to operate the power amplifier without the appropriate

matching network.

CAUTION: The impedance matching transformers used in the matching networks are not

designed for use at low frequencies. NEVER attempt to drive the matching networks at

frequencies less than 500 Hz. Piezoelectric shakers have little or no useful output at low frequencies.

2.3 Matching networks

The operating guide for the particular matching network used will provide detailed information for the

proper use of matching networks. However, information in this section is presented to aid the user in

understanding and applying matching networks.

While an electromagnetic shaker presents a low, relatively constant, largely resistive impedance, a

piezoelectric shaker is essentially capacitive. This means that the impedance presented by the

piezoshaker will decrease almost linearly with increasing frequency. A piezoshaker creates a

97042 Rev A 11/21 Page 10 of 16

displacement proportional to the voltage input for frequencies below its resonance.

Therefore, in order to get maximum displacement and consequently maximum

acceleration levels at low frequencies, the voltage must be stepped up significantly.

The impedance matching network normally consists of a step-up transformer and an output tap

switching arrangement. A variety of output voltages are then available to maximize the voltage

delivered to the piezoshaker at different frequencies. Due to the capacitive nature of the piezoelectric

shaker, the output impedance of the power amp, and the impedance transformation of the matching

network’s transformer, the voltage at the piezoelectric shaker rolls off at 20dB per decade after the

corner frequency (exactly like an RC filter). As the voltage switch setting on the matching network is

switched from highest to lowest setting, the bandwidth of the system will increase. In general,

piezoshakers can be operated at their lower frequencies with the matching network switch in its highest

voltage position. The relatively low load (high impedance) of the piezoshaker at low frequencies is not

demanding and the power amplifier can maintain the high voltage swing for maximum shaker output,

however as the operating frequency increases, lower output voltage taps become more efficient. The

greatest power requirements for the Power Amp will occur at the corner frequencies of the matching

network and shaker system and at the resonant frequency of the shaker.

CAUTION: The piezoshakers can be damaged by internal heat build-up when run at

high levels for extended periods. This is due to the dielectric loss tangent of the

piezoceramic material that generates heat. When driven at high power levels this heat

buildup will raise the temperature of the piezoceramic to the Curie temperature where it

will depolarize itself.

CAUTION: Do not change switch settings of the matching network when there is a

signal present as this may cause the contacts to arc and destroy the switch.

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