14/1/98 Page 3 Issue H
2. Application
The MPR 3E5 is a universal digital adjustable motor protection relay. It serves as overload,
overcurrent, negative sequence (unbalance), and general protection for synchronous and induction
machines. With a large selection of adjustment possibilities, the MPR 3E5 is suitable for almost any
type of machine.
The protective functions of the MPR 3E5 are summarised as follows:
• Thermal Overload protection with adjustable current/time curves and selectable hot/cold
ratios.
• Overload Pre-Alarm with a separate output relay.
• Low Set and High Set Overcurrent Protection
• Single Phasing Protection
• Start Limiter
• Earth/Ground Fault Protection.
• Unbalance (Negative Phase Sequence) protection.
• Incorrect Phase Rotation protection.
• Undercurrent Protection (Definite Time).
• Stall protection using a speed switch input.
• Fully Programmable Output Relay operation.
• Fault trip inhibit setting for Contactor Applications.
3. Features and characteristics
• Complete digital processing of the sampled measured values
• Digital filtering of measured values using discrete Fourier analysis to suppress
high frequency harmonics and D.C. component induced by faults or system
operations
• Self adjusting sample frequency for operation between 40 - 70Hz.
• Extremely wide setting ranges with fine setting steps
• Unauthorised user access control through password protection
• User defined password
• Continuous self-supervision of software and hardware
• Outstanding design flexibility for easy selection of appropriate operational scheme
for numerous applications
• Numerical display of setting values, actual measured values and memorised fault data etc.
• Setting, Measured and Fault Parameters available via RS485 serial link.
• Wide voltage range for DC or AC power supply
• Withdrawable modules with automatic short circuit of C.T. inputs
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General