Frequency, Phase Sequence and Voltage Sensing Relays|Power Distribution Reliability

Frequency Sensing relays

A frequency-sensing relay is a device designed to de-energize an output relay when the input AC frequency reaches an upper or lower limit. When the input frequency passes either of the preset limits (for example, 62 Hz or 58 Hz), the SPDT contacts of the relay drop out to stop a process, sound an alarm, or perform some other desired action. In order to prevent chattering at this frequency, a hysteresis effect has been implemented into its design which separates the dropout point from the pickup point. 

The relay features a solid-state frequency-sensing circuit and a Form C (SPDT) output contact rated for 10 amperes at 120 volts and 60 Hz. The coil is designed to operate continuously at 120 volts AC ± 10%, and it comes enclosed in a nylon dust cover with a standard octal plug for socket mounting.

Phase Sequence Sensing relays

Phase-sequence-sensing relays are used in a range of instrumentation and power-equipment applications where reliable control of three-phase, four-wire power distribution is critical. This solid-state relay features sensors designed to detect any reverse phase sequence in the typical 60 Hz AC current circuits. Loss of one or more phases or even a phase reversal will immediately de-energize the output relay. The relay is typically housed in a protective nylon dust cover and is fitted with standard octal plug-in terminals, allowing for easy socket mounting. Its efficient design makes it an ideal choice for any application where positive control of three-phase power distribution is needed. 

The Phase-sequence-sensing relay provides reliable protection against potential power outages, ensuring optimal performance of related equipment. It is a simple yet effective way to safeguard against reverse phase sequence and other anomalies in three-phase four-wire AC circuits. By installing this relay, you can ensure that your equipment is running smoothly and safely.

Voltage Sensing Relays

Voltage-Sensing Relays are used where a condition of Undervoltage may cause extremely low efficiency, resulting in poor operation or damage to equipment. Unlike current-sensing relays, voltage-sensing relays require a temperature-compensating network due to the resistance changes that occur with fluctuations in temperature. A three-phase voltage-sensing relay senses the lower-than-normal three-phase potential difference and triggers an alarm or de-energizes a process under its control if the potential difference drops below a preset value, even if only one phase is lost. This type of relay includes a general-purpose relay and solid-state sensing circuit enclosed in a nylon dust cover. The contacts are rated for 10 amperes at 120 volts (RMS) and 60 Hz and are designed for single-pole, double-throw operation. The input is designed for 120/208-volts ac at 60 Hz continuous-duty operation in three-phase, four-wire systems with an octal plug for socket mounting.  These relays are highly reliable and provide a great deal of protection against power loss.

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