| |
G8MNY > TECH 13.07.05 17:43l 64 Lines 2740 Bytes #999 (0) @ WW
BID : 54150_GB7CIP
Read: GUEST OE7FMI
Subj: Portable Appliance Testing
Path: DB0FHN<DB0MRW<OK0PPL<DB0RES<DK0WUE<SP7MGD<ZL2TZE<GB7PZT<GB7YFS<GB7CIP
Sent: 050713/1520Z @:GB7CIP.#32.GBR.EU #:54150 [Caterham] $:54150_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (New May 05)
In the UK all commercially used portable mains equipment has to be tested to
ensure it meets basic electrical safety tests.
The 2 basic tests on a 13 Amp plug & test probe are:-
1/ VOLTAGE
Resistance of Live & Neutral to Earth > 500kê @ 500V (DC voltage > 2x RMS).
This test ensures the mains insulation is not too damp or about to break down.
A basic test arrangement might look something like this..
ÚÄÄÄÄÄÄÄÄÄ¿ ____
ÚÄÄÄÄ68KÄÄÄ´Fail/PassÃÄÄo oÄÄÄÄÂÄÄ< L Portable
Mains 500V ³ /³\ ³ Test ³ Appliance
PSU DC ³ DC ³ mA ³ ÀÄÄ< N under test &
³ ÀÄÄÄÄÄÄÄÄÄÙ switched on
EÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄ< E
³
ÀÄÄÄÄÄÄÄÄ> Probe for exposed metal
2/ EARTH CURRENT
Earth case Bond current test up to 25 Amps ( >1.5x fuse rating) with a low
voltage (eg 6V) this equates to a 0.1ê lead R. This test ensures the earth
wiring can withstand the full fault condition fuse rupturing current.
(eg not earthing with a few strands of wire, that would pass A CONTINUITY TEST)
A basic test arrangement might look something like this..
ÚÄÄÄÄÄÄÄÄÄ¿ ____
ÚÄÄÄ0.15RÄÄÄ´Fail/PassÃÄÄo oÄÄÄÄ<E Portable
Mains 6V ³ /³\ ³ Test Appliance
PSU AC ³ AC ³Amps³ under test
³ ÀÄÄÄÄÄÄÄÄÄÙ
EÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ> Probe for exposed metal
More complex testers will measure the values & have different ratings for more
delicate & lower fuse rated items. Some testers do a high voltage flash test
(eg 3KV) to ensure the mains circuit insulation is adequate (eg unearthed TV).
DANGERS
As you can appreciate these tests can be dangerous for some types of equipment.
For instance many electronic items (PC, Audio & Video Mixers, etc) do not have
25A current carrying capacity PCB earth tracks to all of their exposed metal
parts, then PCB earth tracks & fine wires & connectors can BE DAMAGED or even
VAPORISED.
FALSE READINGS
Items that run hot like irons & kettles must have there insulation tested when
cold & when hot, for the test to have any meaning.
Some items can fail a test due to false testing concepts. eg. a long 13A mains
lead wound on a steel winding drum, can fail the earth bond test when the wire
is coiled, but pass when unwound, due to the increase in inductance of the
cable on the steel drum.
Why Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
Read previous mail | Read next mail
| |
