Transcript
Introduction to the Foil Hipot Test
We’ve done hipot testing on the Bolt, testing between the voltage input and user-accessible USB and CT inputs on the other side to test the isolation barrier across the Bolt. Today, we’re going to be doing a different type of hipot test. This measures the isolation from the voltage front end to any sort of user-accessible area outside the Bolt.
If you’re holding the Bolt while an impulsive transient occurs, or you’re holding the CTs, we want to make sure it’s safe, and this is a test that you will also perform on the Bolt. So, let’s check it out.
Test Setup with Copper Foil
We’ll connect the voltage front end and here we have all the voltage inputs tied together to the hot side of the hipot tester. On the other side, we have the CTs. To simulate a person’s hand, we are going to use copper foil tape.
Take this copper sheet, wrap it around the Bolt tightly, and this simulates a person’s hand that might be gripping the Bolt while an impulsive transient occurs. We’re gonna take the return of the hipot tester and actually connect it directly to the copper foil to see if there are any hidden creepage or clearance paths to the isolated side of the Bolt.
Testing the Bolt Housing
We’re gonna start at 4kV, the UL minimum requirement, for five seconds, and we’re allowed a half a milliamp of leakage current. And we easily pass at 48 microamps. Let’s go beyond the minimum to 6kV.
And we easily pass at 80 microamps. Now, we’re gonna go all the way to 8kV to make sure we have a lot of margin in this for the safety test. And we also pass at 8kV.
Testing the CT and Cable Configuration
Now, let’s try this in a different configuration. You may be holding the CTs or the voltage connector, so we’re gonna move the copper foil to a different position.
We’re gonna start back at 4kV and here we have the foil connected around both the flexible CTs themselves and the cable that connects the flex CT elements to the Bolt, in case you’re holding either one of those. We easily pass at 4kV with 32 microamps.
Testing 6kV. And we easily pass, and we’ll go to 8kV to make sure we have a large margin here for safety. And we pass at 8kV.
Testing the Voltage Connector Side
And finally, we’re going to test the other end of the Bolt, the transition between the voltage cable and the Bolt housing itself. Now, we’ve moved the copper foil to the voltage side of the Bolt and again, we’re testing for any sort of hidden creepage or clearance problem that allows a conductive path from the outside of the Bolt, through the voltage connector, into the high voltage section of the Bolt to make sure we have a good safety margin.
Gonna test at 4kV. And we easily pass with 55 microamps of leakage current. Go to 6kV. And we pass there at 6kV. And now we’re going to try 8kV. And we also pass at 8kV.
Summary and Safety Reminder
We’ve passed the foil hipot test in various configurations at the minimum voltage required by UL 6110, and also all the way up to 8kV. This ensures user safety if someone is holding the Bolt and an impulsive transient occurs.
Of course, if you’re using the Bolt with energized conductors, you should still wear gloves, wear the appropriate PPE as required by your utility, but we have an extra layer of safety for those sort of situations.