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On-site Electrical Testing

Houghton International provides a range of non-intrusive on-site tests, which can be used to help identify and diagnose early warning signs before they escalate, potentially resulting in total machine failure, unplanned downtime and excess costs.


Whether a one-off assessment of machine health or as part of your ongoing predictive maintenance schedule, on-site testing is key to identifying any problems early on with minimal disruption.

Dielectric Testing

Houghton International offers a range of non-intrusive condition monitoring including insulation dielectric testing options that can be carried out in situ or in our workshop as part of an inspection or planned overhaul. These tests are designed to assess the condition of windings, diagnose and predict any early signs of deterioration and aging and schedule repairs ahead of a catastrophic failure, which can often be very costly and result in unplanned downtime.

Using an Omicron MPD 800 and CPC 80 + CP TD12/15 tester or Baker DX series and 40kV power pack PP40 tester, our engineers can apply a range of electrical tests to find early indications of insulation weakness and faults in windings, between phases, coil-to-coil and in groundwall insulation. The tests can identify if contamination is impacting insulation strength. They can also detect problems with connections such as feed cable insulation weakness, motor imbalances, and open or high resistance.

These tests are routinely carried out in our electric motor repair shop to demonstrate the integrity of the windings and demonstrate that a motor is correctly wound and insulated, before it is returned to the customer and put into operation.

Further Information

Article: Static motor testing to support preventative maintenance programmes
About Houghton International – brochure download

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Planned preventative maintenance (PPM)

We offer periodic offline testing and trending of the machine’s insulation systems to give an overall picture of winding insulation health. Static or offline testing is performed while the machine is not running and can be executed on site or in our electro mechanical repair facility.

We work with customers to agree the most effective schedule based on their needs and the associated risks. A complete diagnosis of the insulation system offered includes winding resistance, meg-ohm, polarization, step-voltage or high potential (Hi-Pot), and surge testing.

  • Winding resistance testing can find high-resistance connections that lead to current unbalances and eventual failures.
  • The meg-ohm test can determine if the motor is grounded or heavily contaminated by measuring the leakage current through the insulation.
  • The polarization test finds old, brittle insulation and deteriorated ground wall insulation.
  • The step-voltage or high-potential test further stresses the ground wall insulation, and when performed at the motor control cabinet, it tests the cables as well. Cables should be able to withstand the spiking and voltage levels the motor sees; damaged cables can be a real issue.
  • Surge testing allows for the identification of shorted motor conductor turns and failing conductor insulation, which are among the first tell-tale signs of electrical breakdown. The surge test is the only test that can locate weakness within the copper-to-copper insulation, where more than 80% of all winding failures begin.

These tests can be carried out efficiently on site with minimal disruption and the results can then be analysed to make recommendations for future maintenance activity.

Testing high voltage motor using Megger test equipment

Partial Discharge Testing

For higher voltage motors, 6kV and above, Partial Discharge testing can also be used to provide a wider picture of the machine health. High voltage equipment often suffers from Partial Discharge activity, where localised corona or breakdown discharge can damage insulation, leading to progressive degradation and eventual insulation breakdown. This type of issue would not be detected using standard diagnostic tests and it is possible for a motor to appear healthy whilst having high levels of Partial Discharge. Compared with other dielectric tests, the differentiating character of Partial Discharge measurements allows localised weak and aged points of the insulation to be identified.

Combining data with experience enables us to work in partnership with our customers to effectively manage and extend the life of their electro mechanical rotating machinery.

Get in touch with our team today to discuss how Houghton International can support your ongoing electric motor maintenance activities and reduce the risk of unplanned machine failures.

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