Rotor Ground Fault Monitoring Solutions

Advanced Earth Fault Resistance Monitoring for Synchronous Generators

Accumetrics’ Earth Fault Resistance Monitor, Rotor Health Monitor, and Rotor Ground Detection System offer superior ground fault protection of motors and generators. Systems monitor for insulation faults on the field windings of generators and synchronous motors with brushless exciters. They employ advanced wireless techniques to transmit measurement data from the rotor to a stationary receiver unit.

Accumetrics’ Ground Fault Detection Systems are in a class of their own. They provide immediate notification of field ground faults, reducing the risk of prolonged and costly unscheduled outages.

The product line includes three monitoring and detection options designed to retrofit existing generators, plus Accutector, a drop-in replacement for obsolete Rotector Rotor Ground Fault Monitoring Systems with enhanced durability and diagnostics.

 Earth Fault Resistance Monitor AT-8000Rotor Health Monitor AT-8300Ground Detection System AT-8600Accutector Ground Fault Monitoring System AT-9000
(replaces Rotector Model AS-9000)
Monitors for Ground FaultYes Yes Yes Yes
Monitors for Temperature No Yes (12/24 RTDs) No Yes (2 TCs)
Current ShuntNo Yes No Yes
Records Trends Over TimeYes Yes No Yes
Archiving CapabilityYes Yes No Yes
Transmitter MountingEnd-of-shaft / split clamp collar End-of-shaft End-of-shaft Paddle Style
Field VoltageMeasurement Range 0–500 VDC 0–500 VDC 0–750 VDC 0–500 VDC
Maximum Transient without Damage 1000 V for 5 seconds 1000 V for 5 seconds 1500 V for 5 seconds 1000 V for 60 seconds
2000 Vpeak for 1 second
EnvironmentAmbient Temperature 32–185 °F / 0–85 °C at Rotor Module; 32–122 °F/0–50 °C at Receiver Unit 32–185 °F/0–85 °C at Rotor Module; 32–122 °F/ 0–50 °C at Receiver Unit -40–194 °F/-40–90 °C at Rotor Module; -40–140 °F/-40–60 °C at Receiver Unit -4 °F to +158 °F /-20 °C to +70 °C
Rotor Speed 0–3600 RPM nominal; 4320 RPM max 0–3600 RPM nominal; 4320 RPM max 0–3600 RPM nominal; 4320 RPM max 0–1800 RPM nominal; 2350 RPM max
Receiver Power85–250 VAC 50/60Hz or
125–375 VDC <20W
85–250 VAC 50/60Hz or
125–375 VDC <20W
100–240 VAC 50/60 Hz or
24 VDC
100-240 VAC 50/60Hz, 0.5 A
Power to TransmitterInduction Induction Induction Induction
Machine ConnectionsPositive Field Voltage;
Negative Field Voltage;
Rotor Ground
Positive Field Voltage;
Negative Field Voltage;
Rotor Ground; Channel 1 Shunt current + and -; Channel 2 Shunt current + and -; RTDs
Field Negative Terminal;
Rotor Ground
Field Positive Terminal;
Field Negative Terminal;
Rotor Ground;
3x Current Shunt Resistors;
2x Thermocouples
OutputsAlarm Relays; 4-20 mA; Voltage Alarm Relays; 4-20 mA; Voltage Alarm Relays Modbus TCP
Hazardous LocationsN/AN/AN/AClass I, Division 2 Groups A, B, C, and D, T3C

For more information on these systems, see  Ground Fault Protection.