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Current and Voltage Monitoring Relays, Three-Phase
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Current and Voltage Monitoring Relays, Three-Phase
Phase unbalance monitoring
If the supply by the three-phase system is unbalanced due to uneven distribution of the load, the motor will convert a part of the energy into reactive power. This energy gets lost unexploited; also the motor is exposed to higher thermal stress. Other thermal protection devices fail to detect continuing unbalances which can lead to damage or destruction of the motor. The CM range three-phase monitors with phase unbalance monitoring can reliably detect this critical situation.
Phase sequence
Changing the phase sequence during operation or a wrong phase sequence prior to startup causes a change of the rotational direction of the connected device. Generators, pumps or fans rotate in the wrong direction and the installation is no longer working properly. Especially for moveable equipment, such as construction machinery, phase sequence detection prior to the startup process is highly reasonable.
Phase loss
In case of phase loss, undefined stats of the installation are likely to occur. E.g. the startup process of motors is disturbed. All three-phase monitors of the ABB CM range detect a phase loss as soon as the voltage of one phase drops below 60% of its nominal value.
Voltage monitoring
All electric devices can be damaged when operated continuously in a net-work with out-of-range voltages. For example, safe starting is not ensured in case of undervoltage. Also, the switching state of a contactor is not clearly defined when operated in a "forbidden" voltage range. This can lead to undefined states of the installtion and cause damage or destruction of valuable parts.
Extended functionality
ABB’s new generation of three-phase monitoring relays feature additional functions making the application field for the devices considerably larger.
Selectable phase sequence monitoring
The phase sequence monitoring can be switched off by means of a rotary switch or a DIP switch. This enables monitoring of three-phase mains where phase sequence is not relevant for the application, for
example in case of motors with forward and reverse rotation, heating applications, etc.
Automatic phase sequence correction
The automatic phase sequence correction is activated by means of a DIP switch. With activated phase sequence correction, it is ensured that for any non-fixed or portable equipment, e.g. construction machinery, the cor-rect phase sequence is always applied to the input terminals of the load. For details regarding the wiring, please see function description / diagrams.
Characteristics of the CM range three-phase monitors
- Adjustable phase unbalance threshold value 1)
- Adjustable ON-delay/OFF-delay time 1)
- Dual frequency measuring 50/60 Hz
- Powered by the measuring circuit
- 1 n/o contact, 1 or 2 c/o contacts
- LEDs for the indication of operational states
- Multifunctional and single-functional devices
- Phase failure detection
- Phase sequence monitoring 1)
- Over- and undervoltage monitoring (fixed or adjustable)1)
- Wide-range operating voltage guarantees world-wide operation
- Approvals / Marks
 Download the Electronic Products and Relays catalog in *.pdf format
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