DIGITAL TO SYNCHRO CONVERTER

KW960-C

AMI-GFV MARINE

DIGITAL TO SYNCHRO CONVERTER. KW960-C. TECHNICAL MANUAL CONTENTS 1 Contents 2 Data sheet 3 Setting to work 4 Layout and schematics The schematics are from a screen dump and are not fully readable

The picture shows the KW960C with step up transformer adapter mounted underneath.

HEAD OFFICE, SALES AND SUPPORT AMI-GFV Marine Ltd Parham Drive, Eastleigh Southampton SO50 4NU UK Telephone 44 (0) 2380 480450. Fax 44 (0) 2380 480451 Email m.k.woods@btinternet.com Web site www.amimarine.com DESIGN AND MANUFACTURE AMI-GFV Marine Ltd, Cefn Laboratories, Abergavenny UK, Telephone 01873 840405. Fax 01873 840106 Email af-aditel@btinternet.com Web site www.aditel.org.uk Manual written by the designer Andrew Fairgrieve. Last update 09/11/2005

DIGITAL to SYNCHRO CONVERTOR KW960-C

DATA SHEET. The interface receives data by NMEA 0183 and generates a low power synchro, resolver (or sine-cosine) output. The interface will drive typically one or two synchro motors, or numerous electronic interfaces. Applications are to generate gyro compass or wind instrument synchro signals. Log speed and GPS speed to synchro etc is possible. Applications include the retro-fitting of a gyro without a synchro output. The KW960 has a number of different ratios from 1:1 to 360:1. Two KW960s can be used for a coarse and fine servo system as found on military vessels, and with certain gyro compass transmission systems. The adjustable voltage output is about 40 volts maximum, so it can be used for an Anschutz repeater and others directly. For driving known coarse/fine servo systems the KW960’s standard 50v reference output is found sufficient. The synchro frequency is that of the main power input, so for 400 Hz you need a 400 Hz power source. For obtaining 115volt ref, 90 volt signals you a step up transformer adaptor. This is an optional; extra, don’t forget to order it. AMI also make the KW903-SX which is a high power version of the 960 for gyro transmission at 50/60 Hz. SPECIFICATION INPUT: NMEA 0183 heading HEHDT or GPHDT or wind sentence WIMWV. EPROM program DSC5 selects HDT if detected, rejecting sentences such as HDM. EPROM version DSC200 for longitudinal bow water speed from VBW sentence

Scale 200 kts and 5 knots per rev. EPROM version ROLL2 for pitch or roll. $IIXDR,A,x.x,D,A,x.x,D, etc sentence EPROM version DSC40 for longitudinal bow water or ground speed

From VBW sentence. Scale 40 knots. POWER: 115/230v 50 to 400 Hz at 10 VA approx. (Transformer secondary 2 x 25 volts) OUTPUT: SYNCHRO. Nominal 10 to 40 volts line-to-line maximum, adjustable by potentiometer.

5VA total. Virtual centre of 3-phase synchro output is at ground. RESOLVER OPTION. Nominal 20 volts max. (EPROM specific version.) REFERENCE OUTPUT. Nominal 25 or 50 volts, jumper selected.

(An additional transformer adapter is needed for 115v reference, 90v signals.) Reference frequency is that of the power input. Reference output is the transformer secondary.

ACCURACY: +/-1 degree of synchro position. Approx 9 bits resolution.

This accuracy applies to all ratios. NMEA INPUT OPTION: Jumper J3 = 0 = heading. J3 = 1 = Wind angle from $WIMWV input. HEADING RATIO OPTION: Jumper J2 = 1 = 1:1 ratio. J2 = 0 = the ratio as set in EPROM location. Available ratios 9:1, 10:1, 30:1, 36:1, 90:1, 180:1, 360:1 DUAL LOG SPEED. J2 = 1 = 200 kts/rev. J2 = 0 = 5 knots/rev. VERSIONS: Standard bulkhead mounting enclosure 300 x 200 x 155. For a dual (coarse/fine) system 400 x 300 x 155. PRINCIPLES OF GENERATING THE OUTPUT: The input angle is read from the data input. The program rotates the synchro output to any new position, going through all digital states towards it, not just jumping there. This is to attempt to move a synchro smoothly, reducing the jerk caused by any sudden jump of the input. The rotation rate is adjustable by a screwdriver switch from about 2 to 10 degrees per second.

There are 360 “steps” per revolution in the 1:1 mode. The graph shows the relationship of the three voltages. At 60-degree intervals two phases become equal and opposite with the third phase being zero. Measured from ground to the S1, S2, S3 outputs, add 30 degrees to the angle first. 09/11/2005

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SETTING TO WORK POWER SK6 SET THE POWER SWITCH 115/230v. The KW960C suffers massive burn out if you apply the wrong voltage, and of course this is not covered by warranty. The KW960 will operate from 115 or 220v 50/60 Hz and has been used on 400 Hz. On 400 Hz it gives 400 Hz synchro reference and phases output. HEADING, WIND or PITCH AND ROLL NMEA 0183 INPUT SK2 For heading J3 = 0, For Wind J3 = 1. For the log speed version a different EPROM is used. J3 is not used. For pitch and roll another EPROM version is used. J3 is not used. SYNCHRO or RESOLVER/SINE-COSINE OUTPUT SK1 The EPROM must be configured for the output. Location 5C = 00 Hex = resolver or sin-cosine. If 5C is non-zero the output is synchro. OUTPUT RATIO J2 = 1 = 1:1 ratio J2 = 0 = ratio set by location 54 Hex. Values are Hex. 00 = 360:1, 1 rev per degree, the commonest synchro transmission ratio. FF = 180:1. 90 = 90:1. 36 = 36:1. 30 = 30:1. 10 = 10:1. 09 = 9:1 SPEED INTERFACE Program DSC200 and later (DSC205 May 2004) provides 2 scales for a coarse-fine system. J2 = 1 = 0 to 200 knots for 1 revolution of synchro output. J2 = 0 = 0 to 5 knots for 1 revolution. Multiples of 5 knots act similarly; 5-10, 10-15 etc. Zero knots is the synchro natural zero position where two phases are equal and one phase is zero volts. It will doubtless be necessary to change the phase wires to find the right combination for the receiving equipment. It does not matter which KW960 PCB is used for any particular ratio. SPEED INTERFACE Program DSC40 does 40 knots per rev, bow transducer longitudinal speed, using the VBW sentence. J3 = 0 = water speed. J3 = 1 = ground speed. PITCH AND ROLL INTERFACE Program DSCROLL (May 2004) provides1:1 ratio roll and pitch synchro output. In fact it can not know which is roll or pitch, it just uses the first or second data field in the $IIXDR data input. $IIXDR,A,x.x,D,A,x.x,D, cr lf J2 = 1 = use first data field J2 = 1 = use second data field Zero degrees is the synchro natural zero position where two phases are equal and one phase is zero volts. It will doubtless be necessary to change the phase wires to find the right combination for the receiving equipment. It does not matter which KW960 PCB is used for which field.

There is no NMEA 0183 sentence defined for pitch and roll. The nearest I can find is the XDR transducer sentence and this is what is used. SYNCHRO REFERENCE OUTPUT J6 = F = Full reference, normally 50 volts approx J6 = H = Half voltage, 25 volts

EXTERNAL REFERENCE INPUT SK3 This is used to input a LOW VOLTAGE “excitation” voltage, example 2.5 volts RMS 400 Hz. The 3 phase output signals S1, S2, S3 are then at the external reference frequency. This facility is used in instances when an autopilot provides the excitation voltage for a real synchro transmitter. The reference output R1-R2 are not affected, it remains at the main AC input frequency. If you have a 400Hz AC power supply you can run the KW960 from it, and the synchro output will be at 400 Hz.

• ADJUSTING FOR EXTERNAL EXCITATION VOLTAGE INPUT. • REMOVE R19 from its 8-pin socket. • (R19 = 4 x 1K5 is used for internal reference derived from the main AC supply.)

• R20 is an empty position for a 4-resistor network similar to R20.

a. R20 is selected to drop the reference voltage input to about 2.5 volts. b. The resistor does not need to be precise because final adjustment is made using R16. c. The following calculation is approximate. No feedback as to the accuracy of the

calculation has been received.

• Calculate a value for individual resistors in R20. Select a resistor greater than that calculated.

a. At 50/60 Hz i. R Kilohms = ( V - 2) / 27 ii. Example. For 10 volts RMS each R in network = ( 10 – 2 ) / 27 = 296 ohms iii. Use a network of four 330 ohm resistors (RS 434-3727)

b. At 400 Hz

i. R Kilohms = ( V – 2 ) / 20 ii. Example. For 26 volts RMS R = 1.2 K iii. Use a network resistor of four 1K5. (RS 296-6855)

c. Square wave input may be encountered from an autopilot generating its own

reference. Use the formula (b) with a voltage V = peak-to-peak / 4. i. The KW960 will output a distorted square wave due to passing through the

transformer.

• PLUG IN R20.

• It is essential to follow the guidance for adjusting R16

• Do not attempt to connect an external reference supply source to SK1, R1-R2.

VENTILATION The amplifiers run warm. It is a good idea to leave off the gland plate to allow the circulation of air. This is commonly left off to ease the passing of cables. Another idea is to remove the gasket material at the top and bottom of the door. Do not install the KW960 in a very hot place. STEP-UP TRANSFORMER ADAPTER

• Remove the KW960C PCB. • Fit the transformer adapter in its place. • Use M3 30mm spacers to mount the KW960C above the adapter. • Wire across from Synchro output SK1 to the adapter, crossing over R1, R2 • Yes, KW960C R1 to TF960 R2. KW960C R2 to TF960 R1

• The UNLOADED transformer adapter will give out about 120 volts reference. • It drops on load.

DATA OUT LED LD3. DATA TEST POINT J1 LD3 flashes 1 per second in time with the data output. Regular flashing means that the microprocessor circuit is running correctly. Use J1 to monitor the microprocessor operation. A proprietary NMEA 0183 sentence contains in the first field the angle the KW960 is outputting.

STATUS LED LD4

1. OFF = no power 2. STEADY RED = microprocessor not running correctly 3. FLASH RED/GREEN = Processor OK. Data input is NOT CORRECT FORMAT 4. GREEN = Processor OK. Data input is valid and being used

ROTATION SPEED SW1 Adjust this hex switch for an output rotation speed. 0 is the slowest at about 2 degrees per second and 9 the fastest at about 10 degrees per second. The exception is the 1:1 mode where rotation is fixed at about 60 degrees per second. The KW960 can not lose synchronisation with the input. If the output turns too rapidly some repeaters may not keep up, and in any ratio other than 1:1 could slip out of synchronisation. ADJUSTING FOR CORRECT PHASE CONNECTIONS ALWAYS SWITCH OFF BEFORE DISCONNECTING ANY SYNCHRO WIRE. Disconnection can cause a high voltage spike, which might damage the output drivers.

• AT SWITCH-ON in the 1:1 RATIO MODE. This is ideal for setting up the voltage • S1-S2 = 0 volts • S2-S3 = S3-S1 = 0.86 of max phase-to-phase voltage.

• The output waveform is not a pure sine wave. • The S1, S2, S3, frequency is either:

• The frequency of the main supply (J4 and J5 = INT) or a. The frequency of an external reference.

On first testing you may find the repeater turns in the wrong direction, and/or is many degrees out of alignment. Change R1-R2 and S1, S2, S3 wires logically until the repeater indicates and turns correctly. There are 12 possible combinations. Write them down and eventually you should find the correct combination. If you do not, then the repeater itself needs alignment. The natural synchro zero position with one phase measurement = 0v is always assumed to be zero degree, see the graph on the data sheet. TESTING THE KW960 If you have any doubt the first thing to do is to read the data output at J1. It will tell you the settings and show the system is alive and reading the data you input. The data is an NMEA 0183 proprietary sentence, with the angle as the first data field. TESTING THE KW960 OUTPUT

• Disconnect the load, and make sure the jumpers are set for 1:1 option. • (On a different ratio you must make due allowance. A 360:1 ratio means a 1 degree input

change will rotate the synchro 1 revolution back to the same position! Do not be confused.) • Switch on and measure the synchro output voltages. Adjust R16 to the voltage required. • The absolute voltage does not matter, but the ratios do. • To prove each amplifier observe LD5 LD6 LD7, the output LEDS.

o Also measure volts from ground to S1, S2 and S3. Each should be active. • Refer to the graph and the following tables. At 60-degree intervals one LED will go out. Angle S1-GND S2-GND S3-GND LD5 LD6 LD7 030 1 0 1 090 1 1 0 150 0 1 1 210 1 0 1 270 1 1 0 330 0 1 1 Table of angle on 1:1 ratio and voltage on scale of 10 volts. ANGLE S1-GND S2-GND S3-GND ANGLE 0 to 10v 0 to 10v 0 to 10v

000 4.8 4.8 10.0 180 010 6.2 3.1 9.8 190 020 7.5 1.5 9.3 200 030 8.5 0.0 8.5 210 040 9.3 1.5 7.5 220 050 9.8 3.1 6.2 230 060 10.0 4.8 4.8 240 070 9.8 6.2 3.1 250 080 9.3 7.5 1.5 260 090 8.5 8.5 0.0 270 100 7.5 9.3 1.5 280 110 6.2 9.8 3.1 290 120 4.8 10.0 4.8 300 130 3.1 9.8 6.2 310 140 1.5 9.3 7.5 320 150 0.0 8.5 8.5 330 160 1.5 7.5 9.3 340 170 3.1 6.2 9.8 350

TESTING WITH LOAD DIRECTLY CONNECTED (NO TRANSFORMER ADAPTER) • Switch off, connect the load, switch on • Output voltages should remain much the same. Adjust R16 slightly if necessary • Check that the heatsinks do not get very hot. • Synchro repeaters can act as a transformer and feed voltage INTO the KW960, which it

will try to sink, resulting in increased dissipation, which is not wanted. • Rotate the input again; you already KNOW the output rotates correctly. • The synchro repeater should turn.

TESTING WITH A TRANSFORMER ADAPTER

• Measure the voltages at the adapter input, and output, o and you will see them double, OFF LOAD.

• The transformer has internal resistance so the output voltage must drop when on load, just like a signal generator, which has its internal source impedance. You will therefore have to turn the voltage output higher using R16.

• Connect the load and measure the output. • The voltages output may be reduced if the receiver takes power or increased if the

receiver is feeding voltage back into the transformer adapter. • Rotate the input. The synchro repeater should turn in synchronisation.

NOTES ON DRIVING A CONTROL TRANSFORMER CT loads are highly inductive and it is an advantage to tune it by connecting three capacitors across the phases, for they then need less power to drive. I do know an easy method of calculating the capacitors, but values of about 0.1 to 1 microfarad are expected at 60 Hz. The voltage will rise at resonance. Control transformers may be used in a servo loop system, where a feedback circuit searches for a null. Often there is a coarse (1:1) and a fine CT of maybe 36:1. The fine control transformer produces a much more accurate null than the 1:1. Dual KW960’s have been supplied for this application. CT systems will probably work well without the transformer adapter, indeed maybe they will work better for the low impedance source of the KW960 would be applied directly to the high impedance load. NOTES ON DRIVING AN AUTOPILOT Numerous KW960s have been supplied to clients who, so I was told, use them with autopilots. The KW960 is only capable of controlling to 1 degree in the 1:1 mode but this seems to be suitable. There has been very little feedback on how well the autopilot works, just more repeat orders for KW960s. Andrew Fairgrieve