Three-Phase Monitor Relays
Phase unbalance of a three-phase system exists when one or more of the line-to-line voltages in a three-phase system are mismatched. Line-to-line voltages typically vary by a few volts, but a difference that exceeds 1% can damage motors and equipment. How Can I Protect My Equipment?
Macromatic devices work on many systems. Here are the guidelines and recommended connections for Open Delta, Corner Grounded and High Leg (Red Leg, Wild Leg) Delta systems. Contact Macromatic for technical information on other systems.
What Is Undervoltage? How Can I Protect My Equipment? Undervoltage occurs when the average voltage of a three-phase power system drops below intended levels, and is sometimes referred to as a brown-out. Operating in Undervoltage conditions can drastically reduce the life of the electromechanical equipment and lead to premature failure.
When one phase of a three-phase system is lost, a phase loss occurs. This is also called 'single phasing'. What causes a phase loss? How can this condition be monitored and equipment failure and downtime be prevented?
Macromatic Plug-In Three-Phase Monitor Relays provide protection for motors against premature failure caused by voltage faults. This series of relays retain fault indication and continue to monitor all voltages even with a lost phase.
Calculating the Short Circuit Current Rating for control panels requires establishing the SCCR for each of the individual, relevant power circuit components. What about the Phase Monitor Relay used to measure the circuit voltage?
Issue: Schneider Electric (Square D) has obsoleted their complete line of 8430 MPS plug-in & MPD surface-mount phase monitor relays. I see Macromatic has several products I could use to replace the Square D products. Are there any special issues to address? Solution/Resolution: The following are the steps required to replace an obsolete Square D product with one from Macromatic
Issue: I have an application where the panel control voltage is at 120V AC, but I need to have a 24V DC alarm circuit if the three-phase monitor relay trips. How can I do it without adding a relay to the circuit?
Issue: Are fuses required and what size fuse do you recommend using with your Phase Monitor Relays? Solution/Resolution: The use of fusing in-line with Macromatic phase monitor relays is not required; however, Macromatic recommends using a 2 ampere, fast acting, voltage appropriate fuses such as a KTK fuse between the Phase Monitor Relay and the three phases (see diagram below). Use of fusing in-line with loads controlled by the relay output should also be considered depending on the application. Marked safety and regulatory approvals, including UL Certifications, do not require the use of inline fuses in typical applications. Please be aware that different guidelines may apply in your specific application and/or installation.