High Power Digital to Synchro & Amplifier

Dynamic Power Supply
The outputs are powered by an internal, transformer isolated, purely AC dynamic power supply that efficiently transfers the AC reference input power to the outputs, in a natural AC flowing format yielding very low loss.

The power supply produces unfiltered, full-wave rectified positive and negative voltages. These voltages are always in phase with the amplifier output voltages since the power is derived from the reference input. Optimum efficiency is achieved by essentially using as much AC direct power transfer as possible to drive the AC outputs because there is no DC conversion in the power transfer and the amplitude of the internal AC power rails need only be a few volts greater than the voltages driven on the outputs.

Because the outputs are allowed to follow the reference input (synchro’s and converters use ratio accuracy), these supplies only need to be a small percentage higher in voltage than the amplifiers maximum output voltage to accommodate the headroom required of the circuit.

The lower the voltage differential required input to output (considering the internal transformers), to drive the load; the minimum the power loss (in the form of heat), and the greater the efficiency of the amp.

Using this AC pulsating power technique, the output signals are tightly coupled to the reference input and the only power dissipated is the current times the small voltage difference between the pulsating power stage and the synchro signal outputs.

Because both the power stage and the signal outputs are sinusoidal, and the power stages headroom is very small, the power required to drive the load is minimal. Thus the Reference Powered Synchro Amplifiers provide the highest efficiency attainable, low loss, and minimum heat dissipation.

Because there is no internal high frequency PWM or charge-pump switching, there is no RF switching noise emitted from the unit or discontinuity in the outputs to compromise other user circuits, and the outputs are inherently compatible with all and any existing synchro converters.

Using this type of “dynamic power transfer technique,” the efficiency is nominally better than 80% and loss (power dissipation & heat generation) for reactive loads is less than half that of conventional DC powered amplifiers.

Care should be take to minimize the phase shift between the reference and signal inputs. Since the power supplies are only a few volts greater than the signal, the output could be affected by phase shift. Phase shift effect, compensation, and management techniques are detailed in
CCC ap.note#G-SA1 “Driving Synchro Loads.”

Packaging/Conductive Cooling
These models are all self-contained in an easy to install “Bolt-On” bulkhead mount chassis. The chassis is a light weight, single piece aluminum 1/8” thick solid base plate, that provides excellent thermal transfer for conductive cooling of the unit.

Mounting and Thermal Considerations:
Since the unit is primarily conduction cooled, make sure that it is tightly mounted to an appropriately large, thermally conductive (unpainted) surface. Thermal grease can also be applied to the mounting surface.

Kick Circuit
For Torque Receiver applications, a kick circuit is provided to free stalled rotors, simply wire a jumper between the “CO” (current overload) output, and the “Kick” input.

More common an occurrence with large digital or switched step inputs, or after power up; a synchro torque receiver may get hung up at a false null, and just sit there and vibrate while draining large circulating currents. The amplifier will sense the overload that occurs if the rotor is persistently drawing too much current trying (unsuccessfully) to move the shaft load, and (with the kick/CO jumper installed) the amp will automatically shift the output by 120 degrees for a nominal 1/2 second duration to free the rotor from the false null.

Once the rotor is put in motion, it has greater control of its output. Use this feature only if at least one Torque Receiver is being driven from the outputs.

Disable Input
The disable input is a TTL compatible Opto-Isolated input used to provide a circuit-safe means of disabling (turning off & on) the amplifier outputs for various applications. When disabled, the outputs appear as an open circuit to the load.

The disable can be used to sequentially power up the synchro amps if several are used in a power sensitive application, or when used where the synchro signal outputs are going through switching relays for auxiliary, back-up, or test systems.

The disabling the outputs prior to switching either the reference/power inputs or the stator outputs, or both, and then driving the synchro amp inputs to match the angle dictated on the destination source prior enabling the outputs. The relays can very safely switch these points without any appreciable power demand during the actual switching. This will provide a very smooth transition that will reduce surges, and inductive content, allowing the user to minimize the required size of the relays, and dramatically increase the life of any relays used for switching these (high power) terminations. A logic 1 is used to disable the power outputs, a logic 0 will will enable the outputs providing the unit is powered and is not in a thermal overload sensed condition.

BIT Output
The Built-in-test output is a TTL compatible Opto-Isolated output that uses a logic level 1 to indicate that the amplifier has sensed either a thermal overload condition forcing it to shut down its outputs until the internal temperature cools down, or a current overload that is straining and thereby distorting the outputs, until the load is recovered (or kicked to free a stalled rotor), or if in thermal overload (when the internal temperatures sense shuts down the outputs).

Current-Load Sense
The output current on 25VA units is limited to 1.0 amp peak, and approximately 1 amp/25VA on larger units, after a 4 second nominal delay; an over current indication is sensed, setting the BIT output to a logic 1 (see Built-in-test, above).

When Driving Torque Receivers, the current limiting is typically experience whenever the rotor is off null (any significant difference in angle, from where it is being commanded to go), typically activating the kick circuit to rapidly set the driven synchro in motion (to free the rotor from hang-up), allowing the rotor to move towards its commanded angle (=null).

Thermal Sense
These synchro amplifiers are thermally protected, the amplifier outputs will shut down when the internal temperature reaches 125^oC, also setting the BIT output to a logic 1. Thermal overload recovers when the internal temperature recovers.

~~~~~~~~~~~~~~~~~~~~SPECIFICATIONS:~~~~~~~~~~~~~~~~~~~~

Digital Inputs/Outputs: (All Units)
*Disable...Input (DIS): Logic “0” = L=OVDC Enables Power Amplifier Output, TTL Compatible,              requires 2.5ma. at logic 0
          **Isolation: OptoIsolated - 1000V Peak min. Breakdown voltage to Ground.

Built-in-test: Output, Overload Indicator (BIT): logic level 1=H, drives 2 TTL loads, indicates                 amplifier sensed over load condition forcing it to shut down its outputs until                     conditions are satisfied (see txt).
             **Isolation: OptoIsolated - 1000V Peak min. Breakdown voltage to Ground.

 Kick Circuit: Kick & CO (Kick input & current over load); are normally connected for Torque Receiver Loads (not for Passive CT of CDX loads); If Output is hung-up due to excessive current output; Shifts output 120^o for .5 sec. to unjam rotor hang-up. (see txt).

Notes:

* Providing unit is not in thermal overload; internal Temperature is less than 125oC. * Synchro Outputs when disabled are as open circuit, high impedance state. ** On D-S units (having internal Digital to Synchro Converter); no external +5VDC is required, uses internal isolated +5VDC supply, the +5VRTN (see block dia.) is same as the digital data common only.

Signal Inputs:
(A) Synchro: 90VL-L 400Hz +10% (400 Hz)
    Impedence = 400K Ohms min. balanced
(A) Synchro: 90V L-L 60Hz +5 % (60 & 60/400 Hz)
    Impedence = 100K Ohms min balanced
(D) Synchro: 11.8V L-L 400Hz +10%
    Impedence = 26K Ohms min. balanced
(B) **Resolver: 6.81V L-L @ 400Hz or 60Hz +10 %
    Impedence = 4K Ohms min balanced
(C) ***Resolver: 6.0V L-L @ 400Hz or 60Hz +10%
    Impedence = 4K Ohms min balanced

Notes:
  *1) P/N Codes See Model Selection Guide
 **2) Typical Resolver Input format for synchro outputs: when driven by a D-R converter               operating on +15 VDC supplies.
***3)When driven by a D-R converter operating on +12 VDC supplies.

 Signal Input Isolation:
Internally Transformer Isolated; 500VDC min. Breakdown Voltage to Gnd.

DC Power Input for BIT/EN Opto-Isolators:
+5V DC.+10% @ 10ma MAX.
(Not required on -P units, add a P to end of P/N)

Synchro Outputs:

Synchro Output: 90V. Output Models: 90V L-L +1%:
25VA Models: Drives Zso = 243 Ohms (Passive CT & CDX type loads)
             Drives Zss = 6 Ohms (Active Torque Receiver type loads 30VA Models: Drives Zso = 202 Ohms, Zss 6 Ohms
50VA Models: Drives Zso = 122 Ohms, Zss 3 Ohms
100VA Models: Drives Zso = 61 Ohms, Zss 1.5 Ohms

Synchro Output: 11.8V. Output Models: 11.8V L-L +1%:
15VA Models: Drives Zso = 6.9 Ohms
25VA Models: Drives Zso = 4.2 Ohms

*ACCURACY:

+3 arc. minutes for passive CT & CDX loads
+6 arc. minutes typical, +10 arc. minutes worse case for active aTorque Receiver (TR) type loads.
*Shown for Synchro Amplifier Types, for internal 14 bit D-S add 4, 16 bit add 2, arc. minutes.

 *Reference Power Input:(Amplifiers)

**90V. Signals, 25VA Models:
(400 Hz.) 115V. RMS +10%, 360-440 Hz. @ 60 ma.**
(60 Hz.) 115V. RMS +10%, 57-63 Hz. @ 100 ma.**
(60 & 400) 115V. RMS +10%, 57-440 Hz. @ 100 ma.**

90V. Signals, 60 Hz. 100VA Model: (Typical/Measured)
725 ma. no load, +1.122ma. of input/ma. of output.

**11.8V. Signals, 25VA Models:
(400 Hz.) 26V. RMS +10%, 360-440 Hz. @ n1 ma.
        (No load) plus n2 ma. per ma. of output load.

TEMPERATURE: (BEST IN CLASS!)
Operating Temperature Range: -40^oC to +85^oC
Storage Temperature Range: -55^oC to +125^oC

Heat Dissipation:1.5 watts/VA to load. (25 & 30VA.)

Notes:

1. * Reference input must be in phase with signal inputs and signal outputs.
2. ** (No load) plus 1 ma. per ma. of output load.
3. 25VA units; 1 A. typ. draw w/output short circuit.