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I.R Test on an Isolated Motor on a live working Industrial Machine
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<blockquote data-quote="jbingham" data-source="post: 416166" data-attributes="member: 2640"><p>Hi Everyone, Im a new poster. My question regards IR testing a 'locally' isolated 3ph motor on an industrial machine, where the rest of the machine is still powered up.</p><p></p><p>Scenario: This question could apply to numerous machines, but lets say this machine is an oven line with 3ph motors driving various conveyor tracks. The machine has numerous 24VDC sensors, and its PLC controlled. A 3ph motor on one of the conveyors has stopped working and I suspect its 'down to earth'. The motor has a local 3 pole isolator, and I've switched this off. I'd now like to remove the motor terminal box lid and IR test between windings and windings to earth.</p><p></p><p>Q1) Is it ok to IR test (500VDC)? Or is there a risk of the test voltage damaging the sensors elsewhere on the machine or the PLC. If not ok, then why not (i.e how would the test voltage cause damage?). I'm somehow worried about the test voltage going down the motor circuit cpc (or earthed metalwork), and then into earth/neutral busbars inside the control cabinet-where all the PLC and 24VDC circuits are connected. </p><p></p><p>For all I know, industrial sparks may do this all the time. Personally, Ive always powered down the entire machine before IR testing. I want to avoid throwing the main isolator, so that the rest of the machine can continue in process. Also time and hassle would be saved by not powering down.</p><p></p><p>Two more related questions:</p><p></p><p>Q2) Safety: Is it the done thing/necessary to ensure people stand clear of all metalwork on the machine before IR testing - to avoid contact with the test voltage appearing on earthed metalwork?</p><p></p><p>Q3) If I should come across a motor with thermistors in the windings. (therefore, e.g additional 'T1' &amp; 'T2' terminals inside the motor terminal box); What must I do (if anything) to protect the thermistors from the 500VDC test voltage? </p><p></p><p>If there is anything else I need to be weary of when IR testing isolated motors or parts of otherwise live working machines? Any related tips/advice would be appreciated.</p><p></p><p>Thanks In advance, John.</p></blockquote><p></p>
[QUOTE="jbingham, post: 416166, member: 2640"] Hi Everyone, Im a new poster. My question regards IR testing a 'locally' isolated 3ph motor on an industrial machine, where the rest of the machine is still powered up. Scenario: This question could apply to numerous machines, but lets say this machine is an oven line with 3ph motors driving various conveyor tracks. The machine has numerous 24VDC sensors, and its PLC controlled. A 3ph motor on one of the conveyors has stopped working and I suspect its 'down to earth'. The motor has a local 3 pole isolator, and I've switched this off. I'd now like to remove the motor terminal box lid and IR test between windings and windings to earth. Q1) Is it ok to IR test (500VDC)? Or is there a risk of the test voltage damaging the sensors elsewhere on the machine or the PLC. If not ok, then why not (i.e how would the test voltage cause damage?). I'm somehow worried about the test voltage going down the motor circuit cpc (or earthed metalwork), and then into earth/neutral busbars inside the control cabinet-where all the PLC and 24VDC circuits are connected. For all I know, industrial sparks may do this all the time. Personally, Ive always powered down the entire machine before IR testing. I want to avoid throwing the main isolator, so that the rest of the machine can continue in process. Also time and hassle would be saved by not powering down. Two more related questions: Q2) Safety: Is it the done thing/necessary to ensure people stand clear of all metalwork on the machine before IR testing - to avoid contact with the test voltage appearing on earthed metalwork? Q3) If I should come across a motor with thermistors in the windings. (therefore, e.g additional 'T1' & 'T2' terminals inside the motor terminal box); What must I do (if anything) to protect the thermistors from the 500VDC test voltage? If there is anything else I need to be weary of when IR testing isolated motors or parts of otherwise live working machines? Any related tips/advice would be appreciated. Thanks In advance, John. [/QUOTE]
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