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4.2 Safety Testing

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4.2.1 PurposeClassification (inand oneTest line)Sequence Mandate

ProveThe thatproduct's safety class dictates the required test sequence and voltages.

A) Device Classification

Product standards require classification based on the protection method:

  • hazardousClass voltageI stays boxed-in(Earthed): and that accessibleAccessible metal isparts eitherare solidlydeliberately earthedtied (Classto I) or properly insulated (Class II)—with guarded fixtures and rules, not vibes.



    4.2.2 What you actually test (fast map)

    1. Protective Earth (PE) /via the main power cord.
      • Must-Run Tests: Earth Bond, Insulation Resistance (IR), Dielectric Withstand (Hipot).
    2. Class II (Double Insulated): No Protective Earth connection; safety relies on two layers of reinforced insulation.
      • Must-Run Tests: IR, Hipot (Primary – Accessible Metal/SELV).

B) Test Sequence

The test sequence is mandated to prevent equipment damage and ensure reliable results:

Earth Bond – IR (Insulation Resistance) – Hipot (Dielectric Withstand) – (Leakage)

Rule: The system must stop immediately upon any failure. The operator must verify discharge to < 30 V before opening the test enclosure.

4.2.2 Ground Bond Test (PE Continuity)

The Earth Bond —Test verifies the integrity and low resistance of the Protective Earth (PE) path from PEthe power input pin to all accessible metal.metal parts of the enclosure.

  • Setup: Test current must be applied from the PE pin to each accessible metal point (trays, lids, heatsinks). 4-wire measurement is preferred.
  • Test Current: A high AC current (typically 10 – 25 A for 1 – 2 seconds per specification) is injected to simulate a fault condition.
  • Mandate: Scrape pads/serrated washers must be used at the bond points. Failures are often caused by paint under washers or loose lugs.
  • Starter Limit: Resistance must be ≤ 0.10 Ω (including test lead compensation).

4.2.3 Insulation Resistance (IR) and Hipot Testing

These tests stress the insulation using different voltage types to find contamination versus structural breakdown.

A) Insulation Resistance (IR)

IR is a gentle DC test — gentle DC check that insulationfinds iscontamination healthy.(e.g., moisture, flux residue) before heavy stress.

  • Starter Setup: Typically 500 VDC applied for 30 – 60 seconds dwell.
  • Test Pairs: Primary (L+N shorted) – PE/Chassis (Class I).
  • Starter Limit: Resistance must be high, generally ≥ 100 MΩ for benign devices.

B) Dielectric Withstand (Hipot)

Hipot applies high voltage (HV) to verify the structural integrity of the insulation.

  • Voltage Rule: —Typically short,1000 high-voltageVAC stressto between2000 hazardousVAC or equivalent DC.
  • Control the Stress: The test must include a ramp-up time of 1 – 2 seconds and accessiblea circuits.dwell time of 2 – 3 seconds (production) to avoid nuisance trips from capacitive charging.
  • (Failure Management: If yourEMI specY-capacitors callsor it)MOVs cause the AC Hipot test to trip: Leakageswitch Currentto DC Hipot, increase the ramp time, or use the product's designed test bypass (never snip components).
  • Acceptance: —No withtrip mainsat applied,spec; measureleakage touch/earth leakage.

    • Sequence:current Earthmust Bondbe →within IRthe →defined Hipot →window (Leakage)mA scale for AC; µA for DC).

Stop

4.2.4 onStation anySafety fail;and Data Traceability

Due to the high voltages, strict operator safety protocols and rigorous data logging are mandatory.

A) Station Safety Non-Negotiables

  • Interlocks: The test fixture must have an interlocked enclosure where the door locks during HV application. An E-stop must be immediately reachable.
  • Discharge: The system must enforce discharge to < 30 V before opening.the door unlocks; a visible "SAFE" lamp is mandatory.
  • Leads: HV leads must be guarded; alligator clips on painted metal are prohibited.
  • Operator Protocol: The ESD strap must be OFF during HV tests. The "one-hand rule" (one hand only in the cabinet) must be enforced if testing without full enclosure.

B) Data and Audit Mandates

The test system must capture and link all test data to the unit's Serial Number (SN).


  • Data
    Fields:

    4.2.3The log must include the Recipe ID, Class I(I/II), vstimestamp, Classcurrent/voltage IIapplied, (chooseramp/dwell times, and the rightresulting playbook)worst-case Ω for Earth Bond.

  • Log Integrity: Log results must be stored automatically in the MES; manual edits are prohibited.

Final Checklist

Device classMandate

What that meansCriteria

Must-runVerification testsAction

ClassEarth IBond (earthed)

Accessible metal tied to PE (green/yellow)

Earth Bond, IR, Hipot (Primary↔Earth/SELV),Resistance (Leakage if spec’d)

Class II (double insulated)

No PE; reinforced insulation

IR, Hipot (Primary↔Accessible/SELV), (Leakage if spec’d)

Your product standard sets voltages/limits. The values below are starter ranges—always use the recipe from PE/QE.


4.2.4 Station safety (non-negotiables)

  • Interlocked enclosure; door locks during HV; E-stop reachable.
  • Bleed-down to < 30 V before door unlocks; visible “SAFE” lamp.
  • Guarded HV leads; no alligator clips on painted metal.
  • One-hand rule; ESD strap OFF during HV tests.
  • Daily self-test: verify outputs, trip, discharge. Log it.


4.2.5 Earth Bond (PE continuity)

What: Drive a high current through the PE path and measure resistance/voltage drop.

Setup

  • Bond point: PE pin → each accessible metal (trays, lids, heatsinks).
  • Test current: 10–25 A for 1–2 s (per spec); 4-wire preferred.
  • Scrape pads/serrated washers in place (23.1/23.2).

Starter limit: R ≤ 0.10 Ω (include test lead compensation).

Fail fast cues: loose lugs, paint under washers, long star-to-star stackups.


4.2.6 Insulation Resistance (IR)

Why before Hipot: it finds contamination/moisture without heavy stress.

Pairs to test (typical)

  • Primary (L+N shorted) ↔ PE/chassis (Class I).
  • Primary (L+N) ↔ accessible metal/SELV (Class I & II).

Starter setup: 500 VDC, 30–60 s dwell.

Starter limits: ≥ 100 MΩ benign devices; ≥ 10–100 MΩ rugged/EMI-heavy (agree with QE).

Dry to room conditions if humidity just came off a wash/soak.


4.2.7 Hipot (dielectric withstand)

What: apply HV for a short time and ensure no breakdown.

DC vs AC

  • DC Hipot: tolerant of EMI capacitors, clean leakage reading.
  • AC Hipot: stresses both polarities, sometimes required by spec.

Typical pairs & ranges (use your recipe)

  • Primary (L+N tied) ↔ PE/chassis: 1000–2000 VAC or 1200–2800 VDC.
  • Primary ↔ SELV/accessible circuits: same order of magnitude; higher for Class II.
  • SELV ↔ chassis: sometimes required (lower voltages).

Control the stress

  • Ramp 1–2 s → Dwell 2–3 s (longer for bulky filters) → Discharge to <30 V.
  • Trip/leakage windows set per product (mA scale for AC; mA/µA for DC).
  • If EMI Y-caps/MOVs cause nuisance trips: switch to DC, add ramp, or use the product’s test bypass (if designed). Never snip parts.


4.2.8 Leakage current 

(when your standard calls for it)

With mains applied, measure earth/touch leakage in normal and single-fault (e.g., reversed polarity).

  • Use a compliant leakage tester and the network your spec defines.
  • Log mA RMS and test condition. Limits are standard-specific—the recipe must encode them.



4.2.9 Special parts to respect

  • MOVs/Surge suppressors line↔earth: AC Hipot can make them conduct—prefer DC or spec’d bypass.
  • Filters with big Y-caps: expect higher leakage; tune trip and ramp.
  • Paint/oxidation at bonds: zero the surface (bare metal) before retesting.



4.2.10 Data & traceability (attach to the SN)

  • Recipe ID & version, Class (I/II), operator, timestamp.
  • Earth Bond: current, worst-case Ω, points tested.
  • IR: voltage, dwell, MΩ per pair.
  • Hipot: AC/DC, voltage, ramp/dwell, trip setting, max leakage, pairs tested.
  • Leakage (if run): value + condition (normal/single-fault).
  • Fixture/tool IDs and pass/fail decision. No manual edits—MES only.


4.2.11 Acceptance cues (10-second tour)

Area

Accept

Reject

Earth bond

≤ 0.10 Ω; tohigh allcurrent metalapplied.

HighScrape Ω,pad and serrated washer presence verified; high Ω indicates paint under washerthe washer.

IR

StableHipot high MΩ

Drifting MΩ, moisture/contam

HipotIntegrity

No trip at spec;spec cleanvoltage discharge(AC or DC); controlled ramp/dwell time.

Trip,Audit audibleconfirms arcing,test nosystem dischargehandles waitY-caps without false tripping (e.g., using DC Hipot).

Safety Interlocks

LeakageEnclosure (ifinterlocked; run)discharge to < 30 V before access.

WithinOperator recipeprotocol limitensures ESD strap is

OFFOver-limit, noisyduring unstableHV readingtests.

Insulation Check

SafetyIR ≥100 MΩ verified (contamination/moisture check).

DoorTest interlocked;program strapensures OFFdry conditions before final IR test.

Traceability

All parameters (Voltage, Ω, current, ramp time) logged per unit SN.

Open-doorMES tests;must straprecord onthe Recipe ID and version used for compliance.

Rework Rule

If Hipot fails due to paint under lug, surface must be scraped clean and re-tested.

Failure to zero the surface results in recurrence.


4.2.12 Common traps → smallest reliable fix

Trap

Symptom

Fix

L & N not tied for Hipot

Inconsistent stress

Tie L+N together for primary tests

Testing with ESD strap on

Shocks, weird fails

Strap OFF for HV; post a sign on the cage

MOVs/Y-caps tripping AC Hipot

False FAILs

Use DC Hipot + ramp; or enable design bypass

Paint under earth lug

High Ω

Scrape pad, serrated washer, re-torque, measure

No discharge wait

Zaps when opening

Enforce bleed-down <30 V interlock

“Copied limits” from other SKU

Wrong calls

Versioned recipe per SKU/Variant

Bond only at one panel

Floating lids, ESD pain

Bond every metal subassembly <0.1 Ω


4.2.13 Pocket checklists

Before

  • SKU/Variant scanned → correct safety recipe loaded
  • Interlock/E-stop OK; strap OFF; leads/labels checked
  • PE pads bare; serrated washers installed where called

Run

  • Earth Bond: ≥10 A; worst point ≤0.10 Ω
  • IR: 500 VDC; MΩ within limit
  • Hipot: pairs per recipe; ramp/dwell/trip set; discharge
  • (If required) Leakage: mains on; values logged

Close

  • All results to SN in MES; no manual edits
  • Fails to NG-QUAR with pair/step noted
  • Cage tidy; daily self-test tile green



When safety testing is executed with discipline and precision, products leave the line compliant, safe, and ready for global shipment. The reward is confidence—in audits, in the field, and in every customer interaction.

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