Whats a quick way to check a motor's thermals? 3

[Lovison]

Most thermals go to the holding coil on the starters. Is there any other way to wire these up?

Can you check a motor's thermals or is there a test one can do before you actually put them into service?

Please keep it simple electrical components are not my field of expertise - Thanks Wayne E. Lovison
service-parts@naglepumps.com

 

[buzzp]

You can measure the input side and output side to verify continuity while it is disconnected with an ohmmeter. You can measure with an AC volt meter, with the proper rating, between one line in and the same line out. If you read significant voltage here then the thermal is bad. When you can, replace the thermal OL with an electroinc overload device. Good luck and be careful.

 

[Lovison]

buzzp

Thanks for the input. But replace with thermal OL or device
what does it look like? How does it function different from the arrangement?

Where do I get the proper rating to check against? What type of values should I get or they report they are getting?
Are we talking large values or low ones?

Wayne E. Lovison
service-parts@naglepumps.com

 

[peterb]

Wayne, you may need some professional help with this. Buzzp is suggesting that you may want to consider replacing the thermal OL relay and heaters with an electronic overload relay, which is a much more precise device.
Tests before putting the thermal oveload relay into service would include passing current through the relay, using a test set that can provide variable curent and includes a timer to check the operating time to trip - see

http://www.avointl.com,

they (along with others) manufacture this type of test set.

 

[Lovison]

peterb

I appreciate what you're saying. I wouldn't actually being doing this test. I want to tell others what data I would need so as to establish whether or not it really is working.

So far I've found out that there is a procedure for checking this all I want to do now is make sure someone in the field takes the data and reports back their findings. Then I can go back to the motor supplier and ask them if these values are inline with what they are getting.

Thanks for the input Wayne E. Lovison
service-parts@naglepumps.com

 

[buzzp]

So you want to verify the OL works after it is commissioned? The only way to do this,after installation, is to cause an overload condition. Probably the easiest way is to turn the OL setpoint down below the running amps. Based on the percent overload (say FLA is 20 and you set the OL to 10), the time to trip could be measured. This time will vary depending on the TC (trip class) of the overload. So TC of 10 means the OL should trip in ten seconds or less if the amp draw is 600% of OL setting. This is another beautiful thing about most electronic overloads is they have adjustable trip classes and have a wide range of possible trip points. These types could be easily tested in the field. To size the OL you need the motor nameplate data to determine the OL set point, the FLA, the TC, and also you need to consider the control voltage. This is the voltage of the coil on your contactor or starter. The contacts on the OL need to be capable of handling this control voltage (generally control voltage is 240 or less).
My previous post reflects how to troubleshoot a thermal overload moreso than to verify its operation. Hope this helps.

 

[Lovison]

buzzp

Once again you came through. Thanks. Don't worry I have no intentions of messing with these test. But I needed to know what questions to ask and what results to look for.

The plant must have the newer state of the art overload relays you're talking about but we've lost five motors in 60 day to 90 days increments of which can only be caused by overloading.

This overloading should have tripped out the motors long before they got to the roasted stage. We need to find out how they have them wired up and why we're not blowing out the thermals.

I'm printing this data out and thanks again. I can always appreciate someone who knows their trade and can back it up. Thanks again.

Wayne E. Lovison
service-parts@naglepumps.com

 

[buzzp]

Lovison,
This is why I recommend the electronic overload because you can troubleshoot the cause of the overload better. High and low voltages result in an overload condition- this is the only damaging affects of UV and OV (assuming motor is running). People are often surprised when they first install these. The units trip on some condition and they immediately assume the electronic unit is bad. Usually, this is not the case. These devices often shed light on a problem that has been around since the motor was installed. Some will even tell you the time and date of the fault so you can track the origin of the fault. For example, at 9:00 am every morning this electronic relay trips on a low voltage condition. Well this MAY indicate that some large piece of machinery is being started at this time and browning out the power supply of everyone on this same substation. This is just one example.
Thanks for the praise. Buzzp

 

[busbar]

Wayne, you might want to carefully verify that the overload relays are set correctly, and properly applied for the duty at hand. Review all the details of starter/overload-relay instructions. On rare occasions, motor-overload settings get inadvertently 'bumped' or 'inched-up,' possibly by unqualified or misguided individuals for short-term, ‘end-of-my-shift’ gain.

As far as checking the ‘thermals,’ there are specific test sets to do that, like

http://www.phenixtech.com/portablehigh.html

 

[busbar]

Addressing Lovison’s original question, a completely different approach—from a “systems” point of view—would be to apply a pipe wrench to the motor shaft, providing a truly dynamic locked-rotor evaluation of the ‘faster’ end of the relay’s time-current characteristic curve. Make sure it’s a very-strong, well-oversized pipe wrench, though. ;-)

 

[Lovison]

busbar,

I think I'll pass the wrench attempt. Though it has its merits.

Wayne Wayne E. Lovison
service-parts@naglepumps.com

 

[SANSPEUR]

Wayne I notice that you e-mail address is "pumps". You don't state the type of motor or what it is used for. I had a similar problem with an induction motor when the motor was left running and the load was being removed by the operator disconnecting to clean the system. Just a thought.

 

[buzzp]

Some of these overloads have the ability to talk to a computer and log data for you in settable time increments. The faster the time you want, the more money you will pay. I know of one that has this capability that will run you about $1100 for the whole package, minus PC. There are some that also run much higher. Look for these capabilities when searching if you can spend $400-$600(600VAC or less, 3 phase):
Low voltage, High Voltage, Voltage Unbalance, Reverse Phasing, Single Phasing, Overcurrent, Undercurrent, and Current Unbalance.
If you can not spend this much, then just look for voltage monitoring on the main power supply as a start to verify voltage is not a problem. Or just start with one on a couple of motors. There are electronic overloads for medium voltage applications but often require PT's (step down voltage to 120) to monitor the voltage.