RPB / RPA Chattering 2 speed High and Low 3 phase contactors


A chattering contactor is a contactor that rapidly opens and closes instead of maintaining a steady state. This rapid cycling can produce a noticeable buzzing or clicking sound, which is why it's often referred to as "chattering." Addressing it promptly helps maintain system reliability and efficiency.


Chattering contactors are problematic because:


Wear and Tear: It causes excessive wear on electrical and mechanical parts, leading to premature failure.

System Instability: It can create voltage fluctuations, affecting other components and causing malfunctions.

Heat Generation: The rapid switching generates heat, which can damage the contactor and pose a fire risk.

Inefficiency: It leads to inefficient operation of connected equipment, increasing energy consumption and costs.


Symptoms of a chattering contactor include:

Audible Noise: A noticeable buzzing or clicking sound as the contactor rapidly opens and closes.

Intermittent Operation: The connected equipment (like a motor) may start and stop erratically.

Visible Sparking: You might see sparks inside the contactor due to the rapid switching.

Heat Build-Up: The contactor and surrounding components may become unusually warm.

Voltage Fluctuations: Inconsistent voltage readings when measured with a multimeter.

These symptoms indicate that the contactor is not maintaining a steady state, which can lead to further issues if not addressed promptly.


Common Causes:


Voltage Fluctuations: Inconsistent voltage supply can cause the contactor to chatter.

Loose Connections: Poor electrical connections can lead to intermittent contact.

Faulty Auxiliary Contacts: Malfunctioning auxiliary contacts can cause improper control signals.

Mechanical Issues: Worn or dirty contactor components can prevent smooth operation.



Step-by-Step Troubleshooting Guide

  1. Safety First: Ensure the power is turned off before inspecting the contactor.
  2. Visual Inspection:
    • Check for loose or damaged wires using screwdrivers and pliers.
    • Inspect the contactor and auxiliary contacts for signs of wear or debris.
  3. Electrical Testing:
    • Voltage Measurement:
      • Single-Phase Voltage: Measure 230V (or around 240V) between the live and neutral terminals.
      • Three-Phase Voltage: Measure 400V (or around 415V) between any two phases (L1-L2, L2-L3, L3-L1).
    • Continuity Test:
      • Use a multimeter to check for continuity in the control circuit and auxiliary contacts.
    • Control Circuit Voltage:
      • Measure the control voltage (typically 230V) to ensure it is within the specified range.
  4. Mechanical Testing:
    • Manually operate the contactor to check for smooth operation.
    • Clean or replace the contactor and auxiliary contacts if necessary, using contact cleaner and replacement parts.
  5. Control Circuit Check:
    • Inspect the wiring and connections involving the auxiliary contacts.
    • Ensure the control circuit is correctly wired and functioning.

If the issue persists after following these steps, please contact technical support for further assistance. 




Contactor Testing Guide

  1. Isolate Power: Ensure the power to the unit is turned off.
  2. Manual Operation: Push in the contactor using an insulated screwdriver.
  3. Continuity Check:
    • Measure continuity between the contacts. A reading of 0Ω indicates good continuity.
    • If any contacts do not show continuity, the contactor has failed and needs replacement.
  4. Normally Closed (N/C) Contacts:
    • N/C contacts will beep when the contactor is open.
    • The beeping will stop when the contactor is pushed in.
  5. Coil Continuity:
    • Ensure there is continuity between A1 and A2 at all times.
    • If there is no continuity, the coil is open circuit, and the contactor needs replacing.






Common voltage supply issues that can cause a 3-phase contactor to chatter include:


Incorrect Voltage Supply: The control voltage supplied to the contactor coil must be within the acceptable range (typically 85% to 110% of the rated voltage). If the voltage is too low or too high, the contactor may not operate correctly.


Insufficient Current: The control source must provide enough current to pick up and hold the contactor coil. If the current is insufficient, the contactor may chatter as it struggles to maintain the magnetic field.


Voltage Fluctuations: Fluctuations in the supply voltage can cause the contactor to intermittently lose and regain its magnetic hold, leading to chattering.


Debris and Contamination: Debris or oxidation on the pole faces of the contactor can prevent proper contact, causing the contactor to chatter.


Loose Connections: Loose or corroded electrical connections can cause intermittent contact, leading to voltage drops and chattering.


Addressing these issues involves ensuring a stable and correct voltage supply, adequate current, clean contact surfaces, and secure connections.



Common reasons for voltage drop on 3-phase commercial sites include:

Voltage Imbalance: Uneven distribution of loads across the three phases can cause voltage drops on the more heavily loaded phases.

Loose or Corroded Connections: Poor electrical connections can lead to intermittent contact and voltage drops.

Overloaded Circuits: Excessive load on one phase can cause significant voltage drops.

Undersized Wiring: Using wires that are too small for the load can result in higher resistance and voltage drops.

Long Cable Runs: Long distances between the power source and the load can cause voltage drops due to the resistance of the conductors.

Faulty Equipment: Malfunctioning transformers, capacitors, or other components can disrupt the voltage supply.


Addressing these issues involves regular maintenance, proper load balancing, ensuring all connections are secure and free from corrosion, and using appropriately sized wiring.