How to Determine Whether an LS Contactor for Elevators Should Be Replaced

To determine whether an LS brand AC contactor dedicated for elevators (например, MC-18b) needs replacement, assessments shall be conducted from three dimensions: visual inspection, performance testing, and operation status monitoring, in combination with the safe operation requirements of elevator equipment. The specific judgment criteria are as follows:

1. Visual Inspection (to be performed after shutdown and power-off)
2. Contact Ablation and Welding

Open the contactor housing and inspect the surfaces of main contacts and auxiliary contacts: If there is severe blackening, scorch marks, contact welding adhesion, or the contact wear exceeds 1/3 of the original thickness, immediate replacement is required.

Normal contacts shall show the luster of silver alloy. Minor oxidation spots can be removed by wiping, while severe ablation will lead to excessive contact resistance, overheating, and even circuit faults.

2. Coil Damage Signs

Observe the coil appearance: If the coil is charred, the housing is cracked, leads are detached, or the insulation layer is aged and brittle, or a burning smell is detected, it indicates that the coil is damaged and cannot generate normal electromagnetic attraction.

Supplementary test: After power-off, measure the coil resistance with a multimeter in resistance mode and compare it with the official LS parameters (например, the resistance of a 24VDC coil is usually a fixed value). If the resistance is infinite (open circuit) or close to 0 (short circuit), replacement is necessary.

3. Deformation or Jamming of Mechanical Components

Inspect the contact surfaces of the movable iron core and stationary iron core: Obvious rust, деформация, foreign object jamming, or fracture of the shading ring on the contact surface will cause jitter and loud noise during contactor pull-in, and eventually lead to poor contact of contacts.

Check the spring components: If the reaction spring or release spring is fatigued, deformed, or broken, the contactor cannot reset normally and needs to be replaced.

4. Damage to Housing and Terminals

Cracks or damage to the housing will invalidate the IP20 protection rating, making it prone to water or dust ingress and causing short circuits;

Stripped threads, looseness, or ablation of screw terminals will result in unreliable wiring, posing potential safety hazards and requiring replacement.

1. Operation Status Performance Testing (monitored under power-on and load conditions)
2. Abnormal Pull-in and Release

If the contactor generates severe jitter and continuous buzzing noise during pull-in after power-on, it is mostly caused by shading ring damage, foreign objects on the core contact surface, or insufficient coil voltage. If the problem persists after cleaning, replacement is required;

If the contactor fails to release promptly after power-off, or the release delay exceeds 0.5 секунды, it may be due to spring fatigue or contact welding, and shutdown inspection and replacement shall be arranged.

2. Excessive Temperature Rise

During normal elevator operation, detect the contactor housing temperature with an infrared thermometer: If the temperature exceeds 85℃ (or is more than 20℃ higher than that of other contactors in the same circuit) and the housing feels hot to the touch, it indicates poor contact of contacts or coil overload, and replacement is needed.

3. Control Circuit Fault Feedback

If the elevator control system frequently reports contactor status abnormality faults (например, the feedback signal of auxiliary contacts is inconsistent with the actual status), after eliminating line problems, it can be determined that the internal contacts of the contactor are faulty and replacement is required.

III. Service Life and Working Condition Evaluation

1. Reaching the Rated Service Life Limit

The electrical service life of LS MC-18b is 2.5 миллион операций, and the mechanical service life is 15 миллион операций. For elevators with high operation frequency (например, elevators in shopping malls and office buildings), if the cumulative operation count is close to or exceeds the rated service life, preventive replacement is recommended even if there are no obvious faults in appearance.

2. Impact of Harsh Working Conditions

If the contactor operates in an environment with high humidity, heavy dust, or frequent vibration for a long time, or is subject to frequent voltage fluctuations, component aging will be accelerated, and the replacement cycle can be shortened for early replacement.

1. Special Requirements for Safe Operation of Elevators

Elevators are classified as special equipment. If a contactor has any abnormality that may affect safety (например, slight welding of contacts, unstable pull-in), it shall be prioritized for replacement, and operation with faults is strictly prohibited. When replacing, select the same model of LS elevator-dedicated contactor to ensure parameter matching.