Transcript No Slide Title

CTL WORKSHOP 2008
Session 2
“Plug Discharge” Test
Definition of “Plug Discharge”
• Slight misnomer – but “best fit” for the
same test in several standards
• Voltage decay over time?
• Standards targeted:
– IEC 61010
– IEC 60065
– IEC 60335
– IEC 60950
IEC 61010: 6.1.2
• If any of the parts receive a charge from
an internal capacitor, they shall not be
hazardous live 10s after interruption of the
supply.
– 6.3.1a The voltage levels are 33V rms 46.7V
peak or 70V dc (in normal conditions)
IEC 60065: 9.1.6
• Apparatus intended to be connected to the mains
by a mains plug shall be so designed that there is
no risk of an electric shock from stored charge on
the capacitors when touching the pins or contacts
on the plug after its withdrawal from the socket
outlet…
– 2 seconds after the withdrawal of the mains plug, the
pins or contacts of the plug shall not be hazardous
live
– 9.1.1 A part is not hazardous live if the open circuit
voltage does not exceed 35V (peak) ac or 60V dc
• The test MAY repeated up to 10 times to determine the most
unfavorable situation.
IEC 60950: 1 2.1.1.7
• Equipment shall be so designed that, at an
external point of disconnection of an ac mains
supply…the risk of electric shock from stored
charge on capacitors connected in the equipment
is reduced.
– (The circuit has a means of discharge) resulting in a
time constant not exceeding 1s for pluggable type
equipment… Note: during an interval for one time
constant, the voltage will have decayed to 37% of its
original value.
• The relative time constant is the product of the effective
capacitance…. And the effective discharge resistance…. If it
is difficult to determine (these) values, a measurement of
voltage decay at the point of external disconnection can be
used.
IEC 60335-1 :22.5
• Appliances intended to be connected to
supply mains by means of a plug shall be
constructed so that in normal use there is no
risk of electric shock from charged capacitors
when the pins of the plug are touched. …
– One second after disconnection, the voltage
between the pins of the plug is measured with an
instrument that does not appreciably affect the
value to be measured. The voltage shall not
exceed 34V.
– The test is performed 10 times.
So…
• The overall purpose of the cited clauses in
the standard are to ensure that residual
energy in the item under test is not such that
it may cause an electric shock when the item
is unplugged.
• A common method for this determination is to
measure the voltage over time after
disconnection to prove/disprove compliance.
– Some standards allow a calculation in lieu of
measurement if the required information is
available or determinable.
– Laboratories should have capability to make the
measurements.
Whole Group Activity:
• Use the summarised information provided
(plus experience…) to populate the table.
standard
61010
60065
60950
60335
voltage
limit
time
elapsed
to
measure
special instructions/notes
standard
voltage
limit
time
elapsed to
measure
61010
70 V
5s
60065
60V
2s
The test may be repeated 10x. Test
by measurement or calculation
60950
37%, 120V
if we start
with 230V
1s
Voltage decay measurement can be
done instead of calculation
60335
34 V
1s
10x
special instructions/notes
Discussion questions for group
• What voltage comprises “hazardous live”
• Under what circumstances would
“discharge” after disconnection of the
circuit not be dc volts?
05e27..
• Focus on measurement of voltage decay
• Accuracy of measurement
• Generic instructions to cover 4 standards
(apply 230V ac, measure the voltage at 1, 2,
5 and 10 seconds)
• Option to measure 10 times or use
automated equipment
• Opportunity to indicate whether each of the
test conditions on the sample “passed” or
“failed” according to the standards in
question. (Do not answer if your lab is not in scope for the test)
Assessment of Participants:
• Statistical comparison of actual voltage
readings at each time interval
• Determination whether participants
correctly graded the sample according to
the results they submitted (irrespective of
the statistical value of their result)
• Participants divided into groups to ensure
the capability wrt scope is determined
fairly. (If lab equipment is geared to test at a particular
time/condition, the results should be fairly compared with other labs
testing to the same standard)
The samples
• Each sample contained 2 test conditions (A
and B)
• Each test condition was a separate circuit
including resistors and capacitors
• Because of likely homogeneity issues,
program design meant that each sample was
tested by 6 or 7 labs (one after the other)
• Participants were therefore compared only
with a small group
• (And the program takes a long time to complete!)
Assigned Code
Number
TestA overall
Vmax
TestA overall
Vmax
TestA overall
Vmax
TestA overall
Vmax
TestB overall
Vmax
TestB overall
Vmax
TestB overall
Vmax
TestB overall
Vmax
probe
impedance date tested
05e27
1 second
2 seconds
5 seconds
10 seconds
1 second
2 seconds
5 seconds
10 seconds
Mohm
A-6-2
21.5
9.3
0
0
10.5
9.2
3.9
0.9
10
1/06/2007
A-6-3
116
37.5
0
0
219
147
46.9
3.1
1
2007.09.27
A-6-6
120
44
0
0
235
176
72
16
99
5/07/2007
A-6-4
122
48
6
6
224
160
56
12
100
A-6-1
120
44
0
0
216
144
44
12
50
29/11/2007
10th march
,2008
A-6-5
90
30
0
0
170
100
20
0
10
18/01/2008
Table 3: Participant Nominated Pass or Fail of Sample
Test A pass/fail
IEC 60335-1
code
pass
IEC 60950-1
fail
pass
A-6-2
1
A-6-3
1
A-6-6
1
A-6-4
1
IEC 61010
fail
pass
IEC 60065
fail
pass
fail
1
A-6-1
1
1
A-6-5
1
1
1
Test B pass/fail
IEC 60335-1
code
pass
IEC 60950-1
fail
A-6-2
pass
IEC 61010
fail
pass
IEC 60065
fail
pass
fail
1
A-6-3
1
A-6-6
1
A-6-4
1
1
A-6-1
1
1
A-6-5
1
1
1
Group activity
• Study the raw data provided and
determine which laboratories are not in
agreement with the other participants
• Provide possible reasons this has
occurred
• Check the participants’ decisions about
passing/failing of samples. Do you agree?
Outcomes from group activities
• Issues were identified with the results from
participants whose results fell out of the
statistical range.
• Participants were using input impedance that
may not have been suitable for the testing
(100M Ohm probe is recommended)
• Some results did not make sense (eg high
result from a user of a low value probe)
• One participant’s results indicated an
incorrect evaluation whether the sample
passed/failed the standard
Required elements of this test