S11 Series Switching Amplifiers

These amplifiers are normally intended for large systems. They are based on a half bridge, FET switcher PWB, the OUT-11 which is rated at 1,000 VA.

Instruments, Inc. has delivered over 14,000 OUT-11 PWBs since 1987. The reliability of the OUT-11 has been very good. Actual experience has proved greater than a 290,000 hour MTBF per Output PWB.

A pair of boards forms a full bridge. Fast rectifiers and drivers are used for maximum efficiency. Full modulation control is allowed. The transistors are fully protected against load faults, excessive switching frequency, cooling failure, and start-up or power-down transients.

The various models of amplifiers are designated S11-xxm where xx is the number of output boards and m is an optional modifier for special applications. These amplifiers are complete, having a suitable power supply, input preamp and an output filter/transformer system.

Amplifier

Models smaller than the S11-8 are rack mounting, therefore the size and weight is for the amplifier only. The models S11-8 and larger are delivered in a structure (rack), therefore their size and weight is the total and includes the "rack". Multiple cabinets may be designed into a system. We have delivered 3 systems each consisting of 8 S11-64 amplifiers connected to a single load.

The output transformers in models S11-2 through S11-24 are usually mounted from the front. These transformers may be designed for operation down to 50 Hz, however this reduces the high frequency performance and increases the weight slightly. In addition, models smaller than the S11-32 may be designed as specials to pass through a submarine hatch. The larger models have rear mounted transformers which operate down to 300 Hz and are not designed for submarine use.

Model S11-2A is a 2kVA output stage contained in a chassis consisting of minimal metalwork. It is intended to be mounted in a larger chassis, perhaps with other units for a multi-channel system. This output stage does not have a power supply or output transformer, but does include output filtering.

Model S11-36D and S11-36U are multi-channel amplifiers having 18 separate inputs with 18 separate outputs of 2,200 VA each. The output voltage and current from each channel is monitored during the output burst. Values are stored internally in the PM/FL computer and accessable via a front panel switch and displayed on front panel meters. The last known values are displayed until the next burst. These amplifiers are shock mounted for shipboard use.

Interface

The Interface function is accomplished with an analog Pre-Amp, analog output voltage and current monitors, and digital Fault Detection and Fault Location information. If needed, a summing transformer is included for unusual load matching and/or high voltage output.

Power Supply

In our switching amplifiers, reactive currents are returned to the power supply. Thus, when driving a load with a power factor of 0, either capacitive or inductive, the power drawn from the primary AC source is only 15% of the output VA. Any real power delivered to the load increases the primary AC power. With a resistive load, at full power, the overall efficiency is about 75%.

The power supply may be regulated or unregulated. When a regulated supply is used, the DC voltage will be at the rated voltage for the output PWBs, resulting in the maximum output VA possible. Our regulated supplies have a power factor of 70%.

Our unregulated supplies have the advantage of a power factor of 94-98% at full load. The disadvantage of an unregulated supply is that the maximum rated voltage for the output PWBs is established at high line and no load. At low line and full load, the DC voltage is less, therefore the available output VA of the amplifier is less.

OUT-11 1 kW Half Bridge Switching PWB.

(Click image to enlarge)

Specifications for Standard S11 Series Amplifiers

Type of amplifier	Full bridge equivalent, FET output, Switching
Modulation	Squarewave, Stair-Step, or PWM
Load power factor range	0 - 100% capacitive or inductive
Distortion (THD)	PWM: 2% max, 0.2% typical.
Frequency range (-3 dB)	PWM: STD	300 Hz to 20 kHz
		or 600 Hz to 40 kHz
	PMW: LF	50 Hz to 5 kHz
	Stair-Step: max sw freq	160 kHz
RMS noise (PWM only)	-60 dB gated on
- - below max output	-120 dB gated off
Current monitor	100 mV/A
Voltage monitor	2 mV/V
Protection	No combination of passive loads, input signals or
	switch settings will cause amplifier failure.
Fault lights	Temp limit, voltage limit, current limit, blown fuse
Ambient temperature	0 - 40 degrees C
Primary power (standard)	S11-2, 4	208/240 V 60 Hz 1ph
Contact factory for	S11-8 - 24	208/240 V 60 Hz 3ph
other AC voltages	S11-32 - 64	480 V 60 Hz 3ph

Individual Specifications

Model designation	S11-2A	S11-2	S11-4	S11-8	S11-16	S11-24
Output watts - continuous	1,000	1,000	2,000	4,000	8,000	12,000
- 100 sec burst @ 20%	2,000	2,000	4,000	8,000	16,000	24,000
Width (inches overall)	6	19	19	24.5	24.5	24.5
Depth (inches overall)	15	22	22	29.5	29.5	29.5
Height (inches overall)	5	14	22.75	49	62	75
Weight, std	10	140	200	600	1,200	1,400
Weight, low freq (pounds)	NA	170	275	725	1,500	1,750
Amplifier Photograph	S11-2A	S11-2	S11-4	S11-8	S11-16	S11-24

Model designation	S11-32	S11-36D/U	S11-48	S11-56	S11-64
Output watts - continuous	16,000	8 sec on	24,000	28,000	32,000
- 100 sec burst @ 20%	32,000	18 x 2,200	48,000	56,000	64,000
Width (inches overall)	24.5	23.6	24.5	24.5	24.5
Depth (inches overall)	38	25.6	38	38	38
Height (inches overall)	57	67.8	69	75	81
Weight (pounds)	1,600	970	2,000	2,200	2,400
Amplifier Photograph	S11-32	S11-36D	S11-48	S11-56	S11-64

Models with an "A" have no cabinet, power supply, or output transformer.
Models with a "B" have no power supply.

Some models are available in a Multi Channel configuration.
S11-36D or U are 18 channels of 2.2kVA each.
Dimensions with shock mounts and stabilizer 26.0 x 27.3 x 75.9 1050 lb.

Contact the factory for special design limitations and cost.

Specifications and prices subject to change without notice.