Comments by Savino Macias and Boštjan Glavič triggered some thoughts about
EARTH LEAKAGE CURRENT (IEC 60601-1 defined term) and measurement schemes.
1. EARTH LEAKAGE CURRENT in IEC 60601-1 (and most other safety
standards) is the current in the protective earthing conductor from the
equipment to the neutral conductor of the mains supply.
2. The transformer T1 in Figure 13 is a variable transformer (or
equivalent source) to get 110% of the equipment highest rated voltage.
3. The transformer (or source) need not be isolated from the mains as
the point of connection of the leakage current meter, MD, is to the neutral
conductor. Note that the circuit in Figure 13 has one pole of the
transformer connected to ground (making that pole the neutral conductor).
However, the ground is not in the measurement circuit, but the ground may be
important to protect measurement personnel.
4. The MD (Figure 12) measures the voltage across a 1 k-ohm resistor.
Other standards measure the voltage across a 2 k-ohm resistor. The measured
EARTH LEAKAGE CURRENT in IEC 60601-1 is slightly higher than other safety
standards (e.g., those that cite IEC 60990).
5. Supposedly, the resistor values of 1 k-ohm and 2 k-ohm represent the
body resistance at 50 to 60 Hz. Inserting a real body in place of the MD
will result in 10% or less of the measured leakage current.
6. EARTH LEAKAGE CURRENT in IEC 60601-1 (and most other safety
standards) presumes an open ground (fault) in the installation mains supply,
not in the equipment. However, the equipment power cord or plug may get
damaged so as to open the equipment ground connection to the installation
ground. (This is common in North America.)
7. I've often wondered why we measure EARTH LEAKAGE CURRENT with a
simulated body when we're characterizing the equipment. The difference
between the IEC 60990 leakage current measurement circuit and an ordinary
ammeter is at most a 5% pessimistic difference (and even less using the IEC
60601-1 measurement circuit).
Best regards,
Rich
From: Boštjan Glavič <[email protected]>
Sent: Thursday, March 10, 2022 9:38 PM
To: [email protected]
Subject: Re: [PSES] Medical Device Leakage Current Production Line Test
Setup
Dear Savino
Please check specs of your AC programmable source if output is isolated
(floating) . Normally it is not. Therefore additional isolation transformer
is needed.
Best regards
Bostjan
SIQ Ljubljana
Get Outlook za Android <https://aka.ms/AAb9ysg>
_____
Od: Savino Macias <[email protected] <mailto:[email protected]> >
Poslano: sreda, 9. marec 2022 21:33
Za: [email protected] <mailto:[email protected]>
<[email protected] <mailto:[email protected]> >
Zadeva: [PSES] Medical Device Leakage Current Production Line Test Setup
Is anyone familiar with the test setup for doing Leakage Current tests?
I have a device with input voltage of 100-240V, so my production line test
needs to be done at 264V (110% of highest rated voltage).
Would I use a programmable AC power supply to do this test (along with the
leakage test equipment, of course)?
Also, an isolation transformer is required per the 60601-1 standard. Would a
programmable AC power supply act as the isolation or would an isolation
transformer still be needed?
Thanks,
Savino Macias
Canon Virginia Inc.
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