Kirk Kirkland
Electrical Repair Service Co.
Birmingham, Alabama
Technical Education Committee Member

Progressive end users/motor own­ers these days have a greater apprecia­tion for and understanding of motor reliability.

However, many no longer accept the premise that a quality rebuild is accomplished because experienced, well trained technicians serviced a motor and applied static and/or run testing which resulted in a motor with improved reliability. Many end users have developed stringent motor re­pair specifications to which the motor rebuilder must comply. 

More frequently, end users are requiring that the service center pro­vide proof of compliance. This often equates to a series of qualifying tests that may include having the service provider perform a load test on the serviced motor. The load test can be the “acid test” which validates that the repair services rendered meets with the end user’s specifications and/or the original manufacturer’s design criteria. Some end users are exposed to non-compliant issues when their driven equipment is the “load test.” 

Considering the vast array of motor types, not every test system is capable of testing every type of motor under every type of load condition. A detailed study of your customer’s motor types and test requirements will help fine tune the capabilities required for load testing.

It should not be assumed that every repaired motor should be or needs to be load tested. It is up to the service center to examine the needs and requirements of their customers and then make an informed decision regarding the investment in load test­ing equipment. 

The objective here is not to provide instructions on how to load test motors. The objective is to provide tips regard­ing peripherals that may come into play with the purchase and installation of a test stand and a dynamometer.    

Preliminary test stand and dynamometer tips prior to purchase
A critical consideration prior to the purchase of a test stand and/or dynamometer is to thoroughly exam­ine your customer base to determine the size, quantity and types of motors which you know require load testing.

Consider the types of motors that you want to load test, then canvas test stand manufacturers and fully explain, in detail, your requirements. Do not assume that because the test stand is new (or new to you), that it will have all the features you need. When you are canvassing test stand manufactur­ers, drill down on the specifics to make sure that they fully understand the scope of capabilities you require. Buy what you need, not necessarily what is being sold.

Pre-purchase considerations:

• Give serious consideration to hiring a highly qualified elec­trical consulting/engineering firm and involve them from the beginning. They can add value to every dollar you spend on the project. 
• If you are not fully qualified, then hire an electrical contrac­tor with a proven track record. Always double-check their cre­dentials and get references. The contractor will be responsible for power service entry, wiring and connection, components, etc. and work in concert with the consult­ing/engineering firm. Again, compliance with electrical regu­lations will be imperative. The electrical contractor performs the “hands on” electrical construc­tion and installation portions of the project. 
• If utilizing a water brake dyna­mometer, consider including a highly qualified plumbing firm in the mix of service providers. Again, credentials and references are important. Water availabil­ity, pressure, temperature and discharge are critical issues to the operation of water brake dyna­mometers. Follow the dynamom­eter manufacturer’s installation and operational instructions.
• There could be the need to in­volve a civil contractor to handle excavation, base installation and any construction requirements.   
• Facilitate an initial group meeting that includes all your contractors and the test stand manufacturer. It is also a good idea to have the utility and regu­latory representatives present at this meeting as their influence can affect the progress of the project. They should be easier to work with if they are involved at the beginning of the project. The purpose of the meeting is to get all parties on the same page and lay the ground work for each party’s area of responsibility. Each party should then be able to provide you accurate pricing and time lines for your review. Once the project is underway, it is very difficult to change service providers. Continue to facilitate meetings, with all the involved parties, throughout the project.

Whether purchasing a new test stand and dynamometer, or a previ­ously owned unit, the purchase price can be negotiated and becomes basi­cally a fixed cost. Remaining are the costs which are above and beyond the acquisition cost of the test stand and the dynamometer. Hence, the potential for pitfall costs that may require signifi­cant additional expenditures.   

Test stand and dynamometer cost pitfalls

• Your electric utility may pro­vide the power transformer required to power the test stand. If they do provide a transformer, depending on where you are located, there might be an ad­ditional fee on your monthly power bill. This additional fee could come into play even if you provide your own transformer. It is possible that the monthly fee is for an indefinite period of time, or the utility company may offer you a one-time upfront fee. If there are fees involved, examine them closely for their overall effect on costs, short term and long term. The utility fees are additional overhead costs. Be aware of peak demand costs that the utility may implement. Utility-provided transformer costs could range from several hundred dollars (U.S.) a month up to many thousands of dollars (U.S.) depending on transformer and test stand size.
• Consider separate utility meter­ing for the motor test stand. A separate meter will help iden­tify test stand operational costs from other costs associated with general service center operations. You need to be able to measure it in order to accurately charge for it. Check with your local utility before assuming you can get a separate meter. You may run into some resistance, so keep trying.
• Consider having your electric utility “ping” your incoming power supply at random times over several days before you order a new motor test stand. Have documented proof of any potential phase/voltage unbalance issues before instal­lation of the test stand. Phase/ voltage unbalance issues can be troublesome after the test stand is installed and commissioned. For ongoing verification of phase/voltage balance, consider adding metering on the supply side and load side so you can monitor it yourself. The metering is useful to validate that your test stand is not the issue. It is in your favor that the electric utility understands that you are checking on the quality of their power. If there are pre-existing power quality issues, it is recommended to know the severity beforehand. Some test stand manufacturers can com­pensate for utility phase voltage unbalance if they are advised prior to the manufacture of the test stand. Costs for voltage bal­ance correction can be in the tens of thousands of dollars (U.S.).
• Make sure you know your local regulatory requirements for the installation of electrical equip­ment. In the U.S., it is becoming more common for state, county or municipal regulatory agencies to require that the test stand be certi­fied by a Nationally Recognized Testing Laboratory (NRTL). Motor test stands are not normally certi­fied by a NRTL. NRTL certification is best performed at the test stand manufacturing facility. NRTL compliance is confirmed by instal­lation of a certification sticker and registration number on the test stand by the NRTL representative only. There have been instances where the purchaser received a new test stand, and regulatory agencies would not allow commis­sioning or use until certification by a NRTL. On-site certification incurs significant additional costs and will delay commissioning. Test stand certification at the man­ufacturer’s site can range from thousands to tens of thousands of dollars (U.S.) depending on the corrections required by the NRTL. If the NRTL certification has to be done away from the manufactur­er’s location, say at your location, you can count on spending even more money and taking signifi­cantly longer to complete.
• Also in the U.S., impact fees charged by state, county or municipalities for water main taps and/or discharge taps can be significant. Look closely at dumping of used water versus a closed loop system. Both involve significant costs. If you are buy­ing water from a municipality/utility, be aware that many now require the installation, testing and certification of a back-flow-preventer. This device has to be tested and certified upon instal­lation and on an annual basis thereafter. If you have more than one water source, you may need multiple back-flow-preventers. Typical upfront costs can be in the thousands of dollars (U.S.) depending on tap size, your loca­tion and number of taps.

Test stand and dynamometer ac­quisition and installation is a major undertaking. These tips and pitfalls are not inclusive or exclusive of all the challenges one may face. From experi­ence, and as reported by other EASA service centers, unplanned but neces­sary peripheral costs can add signifi­cantly to the overall cost of installing a test stand and dynamometer.

Be aware before hand and hopefully you can plan and budget accordingly.

Categories: Service center equipment, Testing

Tags: Motor testing

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