ROTOR EARTH FAULT DETECTOR

THE ROTOR EARTH FAULT DETECTOR IS DESIGNED TO PICK UP FAULT CURRENTS BETWEEN THE ROTOR FIELD WINDING AND EARTH IN SYNCHRONOUS MACHINES USING INFRA-RED COMMUNICATION.

Due to an increasing demand in rotor diagnostics and telemetry, PPI have designed a low cost, robust solution for detecting rotor earth faults between the rotor and field of synchronous machines.

The devices uses a robust, epoxy moulded Transmitter Unit, mounted onto the rotor shaft at the diode bridge, where it receives its power from the field voltage and continuously measures for any leakage currents between field and earth.

During this stage, a signal is sent to the PT Unit (mounted on the end-frame) to indicate sufficient rotor voltage and healthy operation. During a failure in the rotor insulation, a modulated signal is sent to the frame mounted PT Unit and an alarm is activated on the Receiver Unit.

The Receiver Unit can be mounted anywhere on the machine or inside a control panel. Three outputs are available to indicate Receiver Unit power, Transmitter Unit power and a Rotor Earth Fault Alarm.

The REF Detector is designed for IP66 and operation in Zone 1 and Zone 2 hazardous areas is currently under development.

ROTOR EARTH FAULT BROCHURE

ROTOR EARTH FAULT DATASHEET

ROTOR EARTH FAULT DETECTOR AXIAL

Features & Specs

Transmitter Unit

58VDC – 250VDC field supply
70mA max consumption
100mm transmission distance
Resin filled, aluminium casing
No calibration required
Max speed: 3600rpm
<6kΩ Rotor insulation limit
-40°C – +90°C operating temperature

Receiver Unit

24VDC customer supply
40mA max consumption
‘Comm OK’ Output contacts
‘REF Alarm’ Output contacts
Output contacts available in NO & NC
No calibration required
Reset & Test button for commissioning
-40°C – +60°C operating temperature
Hazardous Cert. available on request

Photo-Transistor (PT) Unit

The PT Unit is mounted on the diode assembly frame and is positioned the end-shield to receive an IR signal in the axial direction. This signal is then electrically transmitted to the Receiver Unit. It is important to align the PT Unit in the correct position to ensure line-of-sight with the transmitter.

Operating principle

Transmitter Unit

The Transmitter Unit is mounted onto the rotor shaft at the drive-end. It receives its power from the field voltage and continuously measures for any leakage currents between field and earth. In a healthy system, a signal is sent to the PT Unit (mounted on the end-frame), indicating sufficient rotor voltage and satisfactory communication. During a failure in the rotor insulation, a modulated signal is sent to the PT Unit and an alarm is activated on the Receiver Unit.

Receiver Unit

The Receiver Unit can be mounted anywhere on the machine or inside the control panel. Three LEDs indicate Receiver Power, Transmitter Power and a Rotor Earth Fault. During healthy operation the first two LEDs are active. Four volt-free outputs are available; two ‘Communication OK’ and two ‘REF Alarm’. These outputs indicate Transmitter Unit power and a Rotor Earth Fault Alarm, respectively.

The Rotor Earth Fault Detector is designed to pick up fault currents between the rotor field winding and earth using infra-red communication.

ROTOR EARTH FAULT DETECTOR RADIAL

Features & Specs

Transmitter Unit

58VDC – 250VDC field supply
70mA max consumption
100mm transmission distance
Resin filled, aluminium casing
No calibration required
Max speed: 3600rpm
<6kΩ Rotor insulation limit
-40°C – +90°C operating temperature

Receiver Unit

24VDC customer supply
40mA max consumption
‘Comm OK’ Output contacts
‘REF Alarm’ Output contacts
Output contacts available in NO & NC
No calibration required
Reset & Test button for commissioning
-40°C – +60°C operating temperature
Hazardous Cert. available on request

Photo-Transistor (PT) Unit

Operating principle

Transmitter Unit

The Transmitter Unit is mounted onto the rotor shaft at the exciter-end. It receives its power from the field voltage and continuously measures for any leakage currents between field and earth. In a healthy system, a signal is sent to the PT Unit (mounted on the end-frame), indicating sufficient rotor voltage and satisfactory communication. During a failure in the rotor insulation, a modulated signal is sent to the PT Unit and an alarm is activated on the Receiver Unit.

Receiver Unit

The Receiver Unit can be mounted anywhere on the machine. Three LEDs indicate Receiver Power, Transmitter Power and a Rotor Earth Fault. During healthy operation the first two LEDs are active. Four dry contact outputs are available; two ‘Communication OK’ and two ‘REF Alarm’. These outputs indicate Transmitter Unit power and a Rotor Earth Fault Alarm, respectively. The Rotor Earth Fault Detector is designed to pick up fault currents between the rotor field winding and earth using infra-red communication.