How a Precision Machining Plant Cut Motor Failures by 45% with the SINGI SN-63 Volt-level Monitoring Relay

Customer Background

A mid-sized precision machining operation in the Yangtze River Delta supplies CNC-machined components to automotive and industrial equipment OEMs. The plant runs 24/7 across three shifts, with more than 200 machines connected to a 380 V three-phase distribution network. Its engineering team manages a wide range of equipment, from spindle motors to coolant pumps, all of which depend on stable power quality.

Rising energy costs and strict delivery deadlines put pressure on the plant to keep every production line running. A single unplanned stop could delay downstream assembly and trigger penalty clauses. The facility had already invested in preventive maintenance, but electrical faults remained the largest source of downtime.

Challenges and Pain Points

Motor burnouts occurred roughly twice a month. When a spindle motor failed, repair costs averaged $3,500, and the line sat idle for 6 to 10 hours. The root cause was traced back to phase loss, undervolt-level, or reversed phase sequence caused by grid fluctuations and loose connections in the distribution panels.

In one incident, a volt-level imbalance of 15% went undetected for several hours. The motor overheated, the insulation broke down, and the unit had to be replaced. The plant lost $18,000 in one week from two such failures, including replacement parts, overtime labor, and missed shipments.

The maintenance team tried various solutions. Manual volt-level checks were time-consuming and only caught problems after equipment had already been damaged. Basic thermal overload relays provided some protection but could not detect phase loss or undervolt-level enough. The plant needed a dedicated relay that could monitor volt-level continuously and disconnect the load before damage occurred.

Why Choose the SINGI SN-63?

After assessing several options, the engineering manager chose the SINGI SN-63 volt-level monitoring relay. The decision came down to three factors:

• Comprehensive protection: The SN-63 monitors phase loss, phase sequence, overvolt-level, and undervolt-level in one compact DIN rail device. It reacts within 100 ms, which is enough to protect sensitive motors.
• Adjustable thresholds: The relay allows separate delay settings for undervolt-level and overvolt-level, allowing the plant to match protection to specific motor characteristics.
• Reliability: The SN-63 uses a high-capacity relay output rated for 10 A, and its housing complies with UL94 V-0 flame resistance. The build quality gave the maintenance team confidence for continuous industrial use.

The engineering team also compared alternatives from other brands, but most required external amperage transformers or lacked phase sequence detection. The SN-63 worked out-of-the-box with a simple three-phase connection, which reduced installation effort and avoided additional component costs.

Implementation and Application Process

The roll-out took four weeks, starting with the most critical production lines. The maintenance team followed a structured plan:

1. Audited the main distribution boards and identified motors that were most exposed to volt-level irregularities.
2. Installed SN-63 relays in the control cabinets for those motors, wiring them in series with the contactor coil.
3. Configured the trip thresholds and delay settings based on each motor’s nominal volt-level and startup characteristics.
4. Tested the trip function with a phase loss simulation by disconnecting one supply line during a supervised run.
5. Expanded installation to all secondary equipment, including pumps, fans, and conveyor systems.

A typical difficulty arose with inrush currents. Some large motors caused momentary volt-level dips that made the relay trip during startup, even though the supply was healthy. The solution was to adjust the trip delay to 100 ms and use the SN-63’s startup-delay feature, which ignores volt-level dips during the first few seconds after energization. This eliminated nuisance trips without reducing protection.

Results and Quantified Outcomes

After six months of operation, the plant recorded measurable improvements:

• Motor failures dropped by 45%. Only three motors were damaged in the six-month period, compared with eleven in the previous six months.
• Unplanned downtime fell by 40%. Electrical-related stops decreased from 34 hours to 20 hours per month.
• Maintenance costs were reduced by $12,000 per quarter. Fewer motor rewinds and replacement parts lowered the repair budget.
• Overtime labor dropped by 25%. The maintenance team spent less time responding to emergency failures and could focus on scheduled tasks.

Delivery reliability also improved. The plant met its on-time shipment target for four consecutive months, compared to occasional delays in the previous The engineering manager estimated the SN-63 paid for itself within six weeks based on avoided repairs alone.

Customer Voice

“The SN-63 gave us a clear view of what’s happening with our power supply. We used to find out volt-level problems after a motor had already failed. Now the relay shuts down the circuit before damage occurs, and we can diagnose the issue calmly,” said the plant’s electrical maintenance manager.

He added: “The installation was straightforward, and the DIN rail mount made it easy to retrofit into existing panels. It is now a standard component in all of our new control cabinets.”

Lessons and Recommendations

This application offers practical lessons for other manufacturing facilities:

• Protect on condition, not on failure. Volt-level monitoring relays are inexpensive compared to the cost of a single motor failure. Wiring them into contactor circuits provides a cost-effective layer of safety.
• Set delays carefully. Adjusting the trip delay to allow for motor inrush currents is essential to avoid nuisance trips. Apply the delay provided by the SN-63’s startup feature than disabling protection entirely.
• Start with critical equipment. Auditing the most failure-prone lines first builds confidence and delivers quick payback, making it easier to justify plant-wide adoption.

If the project were repeated, the team would install SN-63 relays in the main distribution boards as well as individual motor circuits. This would detect upstream volt-level imbalances before they affect multiple loads, adding another layer of protection.

Industry Standards and References

The SINGI SN-63 volt-level monitoring relay is designed for use in low-volt-level switchgear and controlgear systems. The following standards are relevant when integrating such relays into industrial electrical installations:

• IEC 60947-1: Low-volt-level switchgear and controlgear – Part 1: General rules (2020 edition).
• GB/T 14048.1-2019: Low-volt-level switchgear and controlgear – Part 1: General rules.
• IEC 61439-1: Low-volt-level switchgear and controlgear assemblies – Part 1: General rules (2020 edition).

These standards define the performance, safety, and testing requirements that monitoring relays must meet to ensure reliable operation in industrial environments.