Blake Parker
Technical Education Committee Member
Integrated Power Services

Modern testing devices now have more capability than ever. Consider cell phones. They used to be capable of only making a phone call but now act as powerful computers helping us with everything from email, navigation, social media, surfing the internet and more. Modern test equipment has gained multi-function testing capability also. They even package the tests into colorful professional reports. With that being said, do we still need single function equipment to accurately diagnose and perform high quality inspections on electromechanical equipment?

Let’s look at safety first. Multi-function testers (Figure 1) offer high levels of safety for technicians and equipment. Most check ground circuits and will not energize if not properly grounded. They also test for proper connection of the leads and will not energize if all safety conditions are not met. With properly set parameters, the odds of accidentally exceeding proper voltage levels with an automated tester are greatly reduced. Technicians can choose to override the parameters if that function is enabled for the user. While allowing users functionality to select the tests and override the settings is important, ensuring the user understands the proper standards based on the motor rating/design is also critical. The ability to change parameters should be limited to qualified personnel only. This can be controlled through user settings. 

Single function testers (Figure 2) are also very safe for personnel; however, the proper voltage/current level settings are up to the user. The tester does not take into consideration nameplate data or pre-set parameters. Ensuring technicians are well trained and know how to use industry standards such as ANSI/EASA AR100 is critical for assurance of proper test selection, voltage/current settings and pass/fail criteria. 

When looking at the options from a quality perspective, multi-function and single function testers meet industry requirements. Multi-function testers are available that perform insulation resistance, polarization index, winding resistance, surge, partial discharge, hi-pot, inductance tests and more. These testers have automatic settings based on the motor data entered and the parameters set up for them. There are default settings for each that can be modified by the user. The test ranges as well as pass/fail criteria will be auto-selected for the technician when setting up the tester. The test units will then walk the technician through the performance of the tests and generate the data into a customizable report. This minimizes errors in reporting and provides consistency for the shop and its customers. While training is still needed, learning to use a multi-function tester can be easier than multiple single function units. 

When looking at single function testers, there is value in utilizing them as well. At times when a quick test or check is needed, a single function unit may be faster as the setup required is reduced. If a customer sends in a machine and asks for a quick check, attaching an insulation resistance tester to determine if the winding has failed to ground may prevent lengthier disassembly and inspection. Single function testers also allow you to set levels manually, which can be especially useful when troubleshooting. For example, if a winding has failed, utilizing a manual hi-potential tester can be useful in locating the failure point. Automated multi-function machines will trip as soon as the ground is detected, making it harder to find the failure point. While some multi-function testers feature a burn function that allows manual override of the safety trip to find the failure point, it is not available on all units. 

Performing some hi-pot tests such as the graded-time test can require adjustment of time during the test rather than a fixed change over time. This is based on the characteristics of the insulation and performance according to the table provided in IEEE 95. Tests of this nature could be difficult or even impossible to perform using a multi-function tester. When rewinding synchronous rotor poles, a digital low-resistance ohmmeter provides a quick check of the circuit resistance without lengthy setup. The readings from single function testers will need to be compiled into a final report for the customer. 

Other things to consider when looking at the variation between multi-function and single function testers include portability, power requirements, current/voltage capability, database storage and design for field use. Some testers are quite heavy and sensitive to rough handling, while others are designed to be taken to the field and operated off battery power alone. If your shop is involved in a significant amount of field service, battery powered models can improve the efficiency of your technicians in the field. 

When narrowing down what is best for your facility, understanding your customers’ expectations and the market your shop is serving is important. Larger shops that service both medium and high voltage equipment need both multi-function and single function units due to the complexity of work performed. Most low and medium voltage shops would be well served with a multi-function tester and at least one insulation resistance tester. Beyond that, the ability to generate concise reports, technician capability, the need for complex troubleshooting and budget should guide your choice. Most test equipment manufacturers are happy to provide demonstrations at your site to help you decide as well–and of course, you can see test equipment from the leading manufacturers at EASA's Solutions Expo. Rental units are also available to allow for longer-term use. At the end of the day, what is best for your shop often depends on the factors listed above and your personal preference. Just as the multi-tool has not replaced all pocketknives, single function testers will remain valuable in the electromechanical space as well.

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Categories: Technical topics, Service center equipment, Testing, Motor testing, Pump testing

Tags: Test equipment Motor testing

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