MV Tropical


		Points North Ltd.
Marine Gyro Compass / Navigational & Communication Systems Marine Electrical & Electronic Systems

RFA Wave Ruler

Points North Ltd,

Rosyth Europarc, Rosyth,

Fife, Scotland, KY11 2YB

Tel +44(0)1383 417084

Fax +44(0)1383 414677

Mobile 07860 885154

Link to Office View

SYNCHRO RETRANSMISSION UNIT - 903 SM

INTRODUCTION

The 903-SP interfaces either to a gyro or electronic compass. It outputs standard marine synchro transmission of 1 revolution per degree. (360:1 or 360X) and can be used to interface a replacement gyro to existing navigation equipment on the bridge.

HEADING INPUT

The 903 inputs a stepper signal and the “90X 400 Hz contactless synchro” system. The unit will also accept rectified-unsmoothed DC as supplied from some gyros.

For gyros with a 1:1 synchro output, fit a 910 interface, which will produce NMEA 0183 heading for other instruments such as a new radar and ecdis. The 910 can also produce Furuno or Yokogawa data. An alternative is to feed the gyro through a digital and tape heading repeater (991) then to the 903-SP.

BACK-UP NMEA INPUT

You can input NMEA 0183 heading from a second gyro, or magnetic compass. This provides a back-up for the autopilot.

SYNCHRO OUTPUT

The “standard” and most common output is nominally 115v (50/60 Hz) reference, 90v line to line maximum voltage. Synchros are not critical on their voltage. The 903 has several transformer taps to allow voltage selecting. Non standard voltages e.g. Kurs 4, and Plath Navigat gyros. Anschutz repeaters require an external transformer adapter box.

The 903-SP output is generated by solid state techniques. The synchro output rotates through 24 states per revolution with a zero current software controlled switching technique.

SPECIAL CASE: YOKOGAWA

Yokogawa gyros normally use a DC supply to the synchros, but they are still 115v/90v AC synchros. The 903SP can be used without any modification to the voltage.

SAFETY FEATURES

The 903 has an internal alarm buzzer for local operation only, however it also has relay contacts which close in a fault condition. The local alarm has to be cleared by an onboard toggle switch, so access to the 903 is essential. It is recommended a remote alarm and reset is fitted to alert the bridge watchkeeper. The 903 can detect faults in the stepper or NMEA input, and if the synchro output has been overloaded.

CHECK OF EXISTING REPEATERS

When replacing a defective gyro it is essential to check the existing repeaters. One stalled repeater can affect the whole system. All repeaters and the autopilot should be mechanically checked, including the synchro brushes.

SPECIFICATION

INPUT 1: Stepper, 4 to 35 volt steps. + or - steps. (Fit external resistor for higher voltage) or 90x 400 Hz “contactless transmitter” (Like a synchro but with 6 terminals) or NMEA 0183 gyro heading.

INPUT 2: NMEA 0183 heading, magnetic, gyro or Cetrek data.

OUTPUT: Output for nominal 115v ref, 90v synchro, 110v ref, 55v signal

50v ref, 68v signals and Anschutz 50/60v ref 20/24 v signals.

You should specify which on your order.

Synchro output is removed if overload detected.

Reference output 2 Amp. (Fit external transformer if more current required)

Phase output 0.7 Amps per phase. Electronically limited at 2 A.

ALARM RELAY: Held open when OK. Closes on power failure or when alarm is disabled. Pulses when the 903 detects gyro fault, or output overload.

CONTROLS: Input 1, Input 2 changeover switch. Alarm cancel/on/off switch

Main on/off switch. Rotation rate and test select hex switch.

POWER: Nominal 110/220v 50/60Hz at 600VA. Earth is essential.

HOUSING: Duck Egg Green enclosure with door for unattended operation. It should be fitted in a well ventilated location.

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