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Single Phase Voltage Relays

Single phase voltage relays are used in applications where the equipment or controls being operated could operate incorrectly or be damaged by low voltage. These applications usually involve combinations of electro mechanical and solid state controls. As the control voltage drops, some of the solid state equipment may not continue to work correctly, but a contactor or solenoid valve may continue to stay energized. This could be an "out of control" situation. When the voltage goes below a level that is determined to be too low for the controls, the single phase voltage relay will sense that and open a set of contacts. That could shut down the entire control circuit to avoid problems.

Three Phase Voltage Relays

Three phase (3Ø) voltage relays are used in applications typically involving three phase motors. The purpose of the three phase voltage relays is to avoid damage to a motor because of a line voltage problem. The three phase relays monitor the line voltage for problem conditions which can include: Over Voltage, Under Voltage, Phase Loss (Single Phasing), Phase Rotation, and Phase Imbalance. If any of these conditions occur, the three phase relays can be wired into the control circuit to disconnect the motor from the line voltage via a starter or contactor or turn on an alarm. Some units are plug-in, some surface mounted, and some are din rail mounted.

AC Current Relays

Motor over current sensing requirements can occur if:
  • A conveyor jams
  • The motor bearings lock up
  • If the system is full

    Motor and heater under current requirements can occur if:
  • The belt from the motor to the conveyor breaks
  • There is no load on the pump
  • A heater or lamp in a group has burned out

    Motor and heater verifications applications can be:
  • The starter is closed, but the three phase breaker is open
  • Burned out fuses
  • Heater or lamp failure
  • Broken wire
  • CAB

    Pumping, Liquid Level, & Intrinsically Safe Relays

    All of the products in this section are typically associated with pumping applications. The CAB can be used to alternate the operation of two pumps to maintain seals and allow for similar running times. The LL series products are liquid level controls which will accept either float switch or probe inputs. They are typically used to signal the start of a pumping operation for filling (F), draining (D), low and high alarm (A) or dual seal failure (O). The ISR and ISL are relays that provide very low power to switches or probes in a hazardous area to avoid sparks. They have been tested by UL for hazardous locations.

    Zero Speed Sensing Relays

    R-K manufactures two types of speed switches. The CLR uses a proximity switch input and compares the signal to a frequency level. This technique can determine a slow down or stopped condition. The LVM, ZVR, and ZVM monitor the voltage feedback from the motor while it is coasting to a stopped condition. As the motor spins down it acts like a poor generator, but generates enough signal for the LVM, ZVR, and ZVM. When the motor comes to a stopped or very near stopped condition, a relay output is operated.

    Transient Voltage Filters (Suppressors)

    Transient voltage filters are used to suppress the electrical voltage transients that can damage or affect the operation of solid state controls. There are choices of R-C networks (resistor-capacitor) for AC loads, R-D networks (diode-resistor) for DC loads, and voltage clamping units (varistors) for analog control circuits and other loads.

    Transient voltage filters are typically applied in parallel with the coil of the inductive load. Many times the inductive load causing the problem can not be specifically identified, so filters are applied across all of the inductive loads in the control circuit.

    For three phase applications where motors are involved, the transient voltage filter is connected across the phases on the "load side" of the starter. It suppresses the transients that will be generated by the motor after it is disconnected from the line voltage.

    Electronic Timers

    R-K manufactures a variety of electronic timers. All of the basic operations are available. Plug-in timers with relay outputs are available as well as surface mounted solid state ones. They are all adjustable, but can be fixed with specific time delays. Some are available with multiple time ranges (TGM) or multiple time ranges and operational modes (TUB). These make it very easy for maintenance and service personnel.

    Operations Available Include
  • On Delay
  • Off Delay
  • One Shot
  • Interval On
  • Repeat Cycle
  • RD/SD Relay

    Relays & Sockets

    Relays and sockets are used typically in low voltage control circuits (< 240 VAC, 1Ø). They are used to control loads such as starters, contractors, solenoid valves, etc. They can also be used to create control logic when operated with or by remote inputs like limit switches, sensors, pushbuttons, etc. Relays and Sockets can be used to interface PLC or CNC outputs to their inductive loads that may cause damage or draw too much current for the solid state output.

    R-K supplies its line of relays and sockets, RD and RG.
    Embedded Controller with Membrane Overlay

    Custom Products & Processor Based Embedded Controllers