3 min read

Ensuring the optimal performance and longevity of a York Centrifugal Chiller, equipped with a Toshiba motor, is critical. This diagnostic report, utilizing our PDMA MCE/Emax™ tool, highlights the findings from extensive testing to identify and rectify operational issues. 

CHALLENGE  

Reported Faults: The motor exhibited minor inductive imbalance, high running temperatures, hot joints, damaged supply leads with brittle insulation, and inadequately secured supply leads. 

Equipment Model: York Centrifugal Chiller with a Toshiba motor, 402 kW power, operating at 3000 RPM. 

OUR CHECKS 

Type of Assessment: 

1. Testing Equipment and Setup: 

The tests were conducted using our PDMA MCE/Emax™ diagnostic tool, a reliable instrument for motor evaluation. 

The tests included both offline and online diagnostic procedures to assess different aspects of the motor’s performance. 

2. Offline Testing: 

• Motor Details: The motor tested is a Toshiba model with 402 kW power and operates at 3000 RPM. 
  
  Results:  

• The resistance to ground was satisfactory, indicating no major electrical insulation issues. 

• There was a minor inductive imbalance, but it was within acceptable limits, suggesting the rotor was in good condition. 

• The polarization index showed satisfactory results, ensuring the motor insulation was healthy. 

3. Online Testing: 

• Inrush Current Test: The motor’s inrush current was recorded at 1827.29 amps over 4.4 seconds. This high start-up current can be typical but should be monitored for irregular spikes which could indicate underlying issues. 

• Power Quality and Current Analysis: The motor showed a current imbalance of just over 3%, which is acceptable. This imbalance, though minimal, should be kept in check to avoid unnecessary strain on the motor. 

• Temperature Observations: The motor exhibited high running temperatures, with a stator temperature recorded at 85.5°C and bearing temperature at 92.6°C. It is crucial to monitor these temperatures as high levels can lead to premature wear and potential failure. 

DIAGNOSING THE ISSUE   

• Hot Joints and Overheating: There was evidence of a hot joint within the motor terminal, registering a temperature of 110°C. This can lead to insulation damage and increased motor temperatures. Damaged supply leads with brittle insulation were also observed, necessitating replacement. 

• Securing Leads: The motor’s supply leads were found to be inadequately secured, contributing to overheating issues. Proper securing and termination of leads are critical to ensure stable electrical connections and reduce heat build-up. 

solution

• Repair Motor Supply Leads: Replace damaged supply leads and ensure correct lugging to the motor terminal posts. 

• Replace Cooling Fan: The current fan may be undersized. Replacing it with a larger fan can improve air flow and help manage operating temperatures more effectively. 

• Upgrade Thermistors: Install new thermistors to ensure accurate temperature monitoring and protection. 

• Check and Replace Overloads: The high overload temperatures suggest the need for new motor overloads to prevent excessive heating. 

engineer’s note

It is recommended to monitor the motor regularly to track any changes in performance and preemptively address any emerging issues. Regular checks on temperature and electrical parameters will help maintain efficient and safe operation of the motor. 

DO’S & DON’TS

DO’s: 
Regular Monitoring: Monitor the motor regularly to track performance changes and address emerging issues promptly. 

DON’TS: 
Skip Regular Monitoring, Ignore Damaged Leads, Neglect Cooling System, Delay Overload Replacement 

By addressing these issues and following the recommended repairs, the York Centrifugal Chiller can continue to operate efficiently and reliably, providing the necessary cooling capacity without unexpected downtime or maintenance problems. Regular monitoring and maintenance are key to extending the life of the chiller motor and ensuring it functions within its designed parameters. 

Think you have a problem like this one? Contact the Masterflow Helpdesk at 02 9748 2022. Or write to us with your unique situation here (Contact us).