Excitation Loss Module
A loss of generator excitation during parallel operation will result in SPECIFICATION
heavy circulating currents, pole-slipping (loss of synchronisation) There are two versions of the ELM; one for 12V engine battery
and torque/current surges and oscillation. The Stamford Excitation systems and one for 24V.
Loss Module monitors the generator AVR output and signals any
sustained interruption to an integral relay to initiate an SENSING INPUT
indication/alarm. Voltage 0-150 Vdc
Input resistance 100 k ohms
The ELM, which has been specially designed for use with all the Sensitivity 50 v peak
Company’s AVR’s, is powered independently from the engine
battery at 12V or 24V. It operates by detecting the absence of the POWER INPUT
characteristic ‘rectifier ripple’ in the exciter field voltage. An optical Voltage 10-14 Vdc (ELM 12V)
isolator used to ensure complete electrical isolation between the 20-28 Vdc (ELM 24V)
exciter field circuit and the engine battery system. Any loss of AVR Current (standby) 25 ma max all models
output is recognised immediately by the monitoring circuit, and if Relay on 150 ma max (ELM 12V)
the interruption persists for more than about a second the module 60 ma max (ELM 24V)
output energises an integral relay. The changeover contacts can
either provide remote indication of the excitation failure or operate OUTPUT
any other relay-fed protective device. The system incorporates a Single pole changeover relay
time delay to prevent spurious tripping on transients and an over- Rating 5A @ 30 Vdc
rideable eight-second engine-start lock-out. 5A @ 240 Vdc
Power dissipation 3 Watts maximum
• Robust and reliable solid-state electronics.
TIME DELAYS
• Independently powered from engine battery. Response time 1.5-2 seconds
Power up delay 8-15 seconds
• Power supply completely isolated from exciter field.
ENVIRONMENTAL
• Engine-start lock-out time delay. Vibration 20-100 Hz 30 mm/sec
100 Hz - 2 kHz 2g
Relative humidity 95%
Operating temperature -40 to +70°C
Storage temperature -55 to +80°C
GENERAL ARRANGEMENT DIAGRAM
Not suitable for mounting in generator terminal box. Switchboard or bedplate mounting recommended.
CONNECTION DIAGRAM
Barnack Road • Stamford • Lincolnshire • PE9 2NB
Tel: 00 44 (0)1780 484000 • Fax: 00 44 (0)1780 484100
© 2005 TD_ELM.GB_07.05_02
