LED Strip leaking AC reading.

Thread Starter

Benx

Joined Jun 2, 2017
13
I opened up a LED lamp that measured leaking AC voltage 70 Vac and sometimes after on is 78 Vac or so. The volt is stable AC and DC no reading.
I have checked with LED lights ON, the leakage is not from the driver, connectors,.... I isolated all drivers, connectors,.... away from frame to determine no AC leak but only LED strip that is glued to the frame. So last result LED strip leaked this AC voltage.

LED Driver Specification: 2 wires, AC 240 Vac 0.33A to 2 wires 24-40 Vdc, max 36W, max 900mA SELV.
LED connection: 5 LED in series, Total LED 120, type 5050 LED.
Measurements:
Driver output NO LOAD: 104Vdc
Driver output LED all ON: 72.8Vdc, 160mA
Ground to LED Strip Negative: 30M ohm
Ground to LED Strip Positive: 40M ohm.

Question:
Why is leaking AC, not DC?
What is SELV?
 
Last edited:

Ya’akov

Joined Jan 27, 2019
9,265
Welcome to AAC.

How did you measure the “leakage”?

SELV is “Separated Extra Low Voltage” which is a designation for a circuit that provides <50VAC or <120VDC (ELV). It is distinguished from other arrangements (PELV—”Protected” and FELV—“Functional”) in that a single failure in another circuit, including a ground fault, cannot cause a voltage in excess of ELV.
 

Thread Starter

Benx

Joined Jun 2, 2017
13
Welcome to AAC.

How did you measure the “leakage”?

SELV is “Separated Extra Low Voltage” which is a designation for a circuit that provides <50VAC or <120VDC (ELV). It is distinguished from other arrangements (PELV—”Protected” and FELV—“Functional”) in that a single failure in another circuit, including a ground fault, cannot cause a voltage in excess of ELV.
From Ground of frame to AC ground.
 

Ya’akov

Joined Jan 27, 2019
9,265
From Ground of frame to AC ground.
Do you have a low impedance (Low Z) DMM? It is likely the case that the voltage you are measuring is at such a small current that any load at all will cause it to read as 0V. A high impedance DMM will show you a voltage that can’t really exist if it has to do anything.
 

Thread Starter

Benx

Joined Jun 2, 2017
13
Do you have a low impedance (Low Z) DMM? It is likely the case that the voltage you are measuring is at such a small current that any load at all will cause it to read as 0V. A high impedance DMM will show you a voltage that can’t really exist if it has to do anything.
I used a Fluke 78, doubt it has Low Z function. I used a very good test pen and tested lit when it touched on the frame.
What do you mean of this? "It is likely the case that the voltage you are measuring is at such a small current that any load at all will cause it to read as 0V." I measure from frame to ground AC is 70 Vac. However I dare not measure Ampere from LED Frame Ground to AC Ground because it may trip the ELCB.
 

Sensacell

Joined Jun 19, 2012
3,502
There is always some capacitance between the LINE and ground in any device powered by mains voltage.
Transformer inter-winding capacitance, EMI suppression capacitors etc all contribute to this leakage.
DC current cannot flow through capacitors, so you should only see an AC leakage voltage.

The leakage current should be very low, if you measure 70 VAC on your 10 Megohm multimeter, this represents a leakage current of 7 uA, which is totally acceptable.

Try measuring again with a 10K resistor across the meter terminals to reduce the impedance.
 

Ian0

Joined Aug 7, 2020
10,276
The limit is 750uA on most standards, determined by connecting a resistor (22k, I think) between the case and ground and measuring the voltage across it.
 

Ya’akov

Joined Jan 27, 2019
9,265
I used a Fluke 78, doubt it has Low Z function. I used a very good test pen and tested lit when it touched on the frame.
What do you mean of this? "It is likely the case that the voltage you are measuring is at such a small current that any load at all will cause it to read as 0V." I measure from frame to ground AC is 70 Vac. However I dare not measure Ampere from LED Frame Ground to AC Ground because it may trip the ELCB.
Does using Low Z mode change the reading?
 
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