Touch (Leakage) Current Hazard Based Safety Engineering - Touch (Leakage) Current

Touch (Leakage) Current Overall Session Objectives: 1. To understand the rationale for the Touch (leakage) Current Test, instrumentation, connections, test procedures and limits 2. To understand limitations of test and alternative approaches

Touch (Leakage) Current Touch (Leakage) Current Topics Definitions (UL 101, IEC 60990) Touch current paths Physiological effects of touch current (electric shock) Body impedance models and “safe” voltage limits Touch (Leakage) Current Test Touch current instruments (meters) Measurement circuits and procedures Limits Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current DEFINITIONS LEAKAGE CURRENT (UL101-2002): Electric current which flows through a person upon contact, between accessible parts of an appliance and (1) ground, or (2) other accessible parts of the appliance TOUCH CURRENT (IEC 60990): Electric current through a human body or an animal body when it touches one or more accessible parts of an installation or of equipment. Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Paths Accessible metal Ungrounded Conductor L + Touch current Load V S Load _ Grounded Conductor N Return Path Electrical insulation System Grounding (protective earthing) Conductor G ? Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Touch Current Paths Touch (Leakage) Current Example: Ungrounded 2 wire Cord and Plug-Connected Appliances To Electrical Supply Load Load Electrical Insulation System touchable metal Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current radio Can opener TV Toaster oven blender Coffee maker iron Examples of 2-wire Non-Grounded Appliances Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Touch Current Paths Return Paths-1 Ungrounded Conductor Touchable metal L Ungrounded 2 wire appliance Touchable metal + Load V S Load _ Grounded appliance Grounded Conductor N G Electrical insulation System Grounding (protective earthing) Conductor Touchable Metal of Grounded Appliances G Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Equipment Grounding Conductor (protective earthing conductor) Touch Current

Touch (Leakage) Current microwave radio Coffee maker range Can opener TV Toaster oven refrigerator blender dishwasher iron Examples of 2-wire Non-Grounded Appliances Examples of 3-wire Grounded Appliances Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Touch Current Paths Return Paths-2 Ungrounded Conductor Touchable metal L Ungrounded 2 wire appliance Touchable metal + Load V S Load _ Plumbing Fixtures Grounded Conductor N G Electrical insulation System Grounding (protective earthing) Conductor Construction Grounds G Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Touch Current Metallic Piping System Bonding connection to water pipe

Touch (Leakage) Current microwave radio Coffee maker Sink Can opener range TV Toaster oven refrigerator blender dishwasher iron Baseboard heating Examples of 2-wire Non-Grounded Appliances Examples of 3-wire Grounded Appliances Examples of Construction Grounds Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Touch Current Paths Return Paths-3 Ungrounded Conductor Touchable metal L Ungrounded 2 wire appliance + Load V S Load _ Grounded Conductor N G Electrical insulation System Grounding (protective earthing) Conductor Pathway through earth Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Soil Touch Current

Touch (Leakage) Current Touch Current Paths Touch (Leakage) Current Example: Three - Wire Grounded Cord and Plug Connected product Ungrounded Conductor Touchable metal L + Load V S Load _ Grounded Conductor N G Electrical insulation System Grounding (protective earthing) Conductor Potential Touch Current Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Touch Current Paths Touch (Leakage) Current Touchable metal Load Electrical insulation System L N G + _ V S Ungrounded Conductor Grounded Grounding (protective earthing) Example: Three - Wire Grounded Cord and Plug Connected product Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Example: Three - Wire Grounded Cord and Plug Connected product Connection to Ungrounded Receptacle Ungrounded Conductor Touchable metal L + V S Load _ Grounded metal Grounded Conductor 3 to 2 adapter N Open circuit or high impedance (fault) G Grounding (protective earthing) Conductor Electrical insulation System OR 2-wire receptacle (normal- old construction) Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Touch Current

Touch (Leakage) Current Touch Current Paths-4 Touch (Leakage) Current Touch Current From Simultaneously Touchable Parts of same product Ungrounded Conductor touchable metal L + Load Load Z V S _ Grounded Conductor N G Grounding (protective earthing) Conductor Touch Current Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Touch (Leakage) Current Topics Definitions (UL 101, IEC 60990) Touch current paths Physiological effects of touch current (electric shock) Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Physiological Effects of Touch Current (sinusoidal, rms, 60 Hz) Perception (microamperes to 0.5 mA) Startle reaction (> 0.5 mA) Muscle tetanization (inability to let go) (> 5 mA) Ventricular fibrillation (> 50 mA) Electrical burns (> 70 mA) Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ V10-001

Touch (Leakage) Current Effects of Frequency on Electric Shock Thresholds and Limits for Continuous AC current 10 3 IEC Threshold UL Limit Ventricular Fibrillation 10 2 0.716 I = 0.954 f (see note 3) f > 70 Hz 35 2 Let-Go 20 Body Current (rms mA) I ~ 0.0007 f f > 1 kHz 10 5 Startle Reaction 1 1. threshold/limit = 2 mA at 0 Hz (dc) 1 2. In the case of let-go, IEC curve represents average value 0.5 3. respiratory arrest observed in dogs at 20, 30, and 40 mA Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ 10 -1 10 2 10 3 10 4 5 10 6 10 10 Frequency (Hz)

Touch (Leakage) Current Other Touch Current Variables Waveshape* Duration* Current Density Pathway through body (skin contact location) Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ * See Special Situations for Touch Current Measurements V10-015

Touch (Leakage) Current Touch (Leakage) Current Topics Definitions (UL 101, IEC 60990) Touch current paths Physiological effects of touch current (electric shock) Body impedance models and “safe” voltage limits Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Determining Touch Current Voltage Source Z S + Z B I B V s _ V s I B = body current I B = V s Z S Z B = source open circuit voltage + Z S = source impedance ( f , .....) Z B V S = Z S , Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Z B = body impedance

Touch (Leakage) Current Five Component Body Impedance Model Impedance representing one skin-electrode contact C 1 R 1 R 3 Internal body impedance (less the skin) Impedance representing other skin-electrode contact C R 2 2 Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Effect of Current Pathway on Internal Body Impedance Internal Body Impedance (R3) (typical adult) Elbow- 200 ohms Torso- 100 ohms Wrist- 300 ohms Knee- 150 ohms Ankle- 350 ohms CLASS EXERCISE: What is the internal body impedance: Hand to hand? _________ohms One hand to both feet? ________ohms Both hands to both feet? ______ ohms Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Simplified Body Impedance Models 3-component model for dry-moist contact and low touch voltage Combination two large area skin contacts Conservative model for low skin impedance (e.g., wet contact, high voltages, and/or high frequency) 0.22 Microfarad 1500 ohms 500 ohms 500 ohms Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Internal body impedance

Touch (Leakage) Current Combined Effects of Frequency on Body Impedance and Electric Shock Thresholds Z Body Impedance Frequency in Hertz 10 100 1000 10,000 I Body Current Threshold for Let-Go Frequency in Hertz 10 100 1000 10,000 Applied Voltage Threshold For Let-Go E = I x Z Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Frequency in Hertz 10 100 1000 10,000

Touch (Leakage) Current Examples of "Safe" Voltage Criteria (Check the specific end-product standard) Let-go and fibrillation, dry locations (UL, NEC)  30 V AC rms (< 100 Hz)  60 V DC Let-go and fibrillation, wet locations, not including immersion (UL, NEC)  15 V AC rms (< 100 Hz)  30 V DC Immersion conditions Generally no “safe” voltages Dry locations where startle reaction cannot be tolerated (UL)  42.4 V peak (< 100 Hz) (including dc) IEC SELV circuits: normal conditions and single fault conditions for time > 0.2 sec  42.4 V peak (< 100 Hz)  60 V DC Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ single fault conditions for time < 0.2 sec  71 V peak (< 100 Hz)  120 V DC

Touch (Leakage) Current Electrical Insulation: Basic Equipment Safeguard Against Electric Shock Zs ZI ZB + IT Vs IS _ Vs = source voltage ZI = insulation impedance IS = available source current Zs = source impedance ZB = body impedance IT = Touch current Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ VS exceeds “safe” voltage AND Hazardous voltage and current source: IS = VS / Zs exceeds “safe” available current

Touch (Leakage) Current Basic Tests on Electrical Insulation Electrical insulation model Touch (Leakage) Current Test Insulation Resistance Test Dielectric Withstand Test (Hi-pot) Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Touch (Leakage) Current Topics Definitions (UL 101, IEC 60990) Touch current paths Physiological effects of touch current (electric shock) Body impedance models and “safe” voltage limits Touch (Leakage) Current Test Touch current instruments (meters) Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Test Ungrounded Conductor Accessible metal MEASUREMENT INSTRUMENT L + Load V S Load _ Grounded Conductor N Electrical insulation System Grounding (protective earthing) Conductor G applies when source exceeds “safe” voltage levels Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ represent body impedance as function of frequency represent physiological effect as a function of frequency

Touch (Leakage) Current Selection of Measurement Instrument Instrument Specifications SPECIFICATIONS FOR REACTION: (0.5 mA rms limit @ 60 Hz) ANSI C101- 1986 - Average Responding System (ARS) (Still specified in most UL standards) UL 101- 2002 (Replaced ANSI C101)(Specified in some UL end product standards and most harmonized UL standards) IEC 60990 – 1999 SPECIFICATIONS FOR LET-GO: (3.5 mA rms, 5 mA rms limits @ 60 Hz) IEC 60990 - 1999 SPECIFICATIONS FOR ELECTRICAL BURNS: (70 mA rms) UL101- 2002 Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ IEC 60990 - 1999

Touch (Leakage) Current Measurement Instrument Specifications for Reaction Average Responding System (ARS) (ANSI C101- 1986) 0.15 u F C1 1500 Ω R1 M Ammeter (average responding) (a) Input impedance (Z) (intended to combine effect of frequency on body impedance and physiological response) Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ (b) Meter type and location

Touch (Leakage) Current Measurement Instrument Specifications for Reaction Average Responding System (ARS) (ANSI C101- 1986) IA = actual current to network IA I1 = indicated current to network ( = V1/R1 rms for sinusoid) IA II / Z R1 = Z = R1par C1 (0 - 100 kHz) V1 M VM I1 1500 Ω R1 0.15 uF C1 Voltmeter (average responding) Indication (current) = 1.11 x VM (ave)/1500 (a) Input impedance (Z) (combines effect of frequency on body impedance and physiological response) (b) Meter type and location = I 1 = V1 / R1 ( rms for sinusoid) Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ (c) Meter indication Max 5% error @ indication of 0.75 mA (d) Circuit frequency response ( 0 to 100 kHz)

Touch (Leakage) Current Simpson Model 229 (ANSI C101- 1986) Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Revised Measurement Instrument for Reaction 20 50 60 100 200 500 1000 2000 5000 10000 20000 50000 100000 200000 500000 1000000 Freq (Hz) 1998 1990 1986 1961 1857 1433 973 661 512 485 479 477 476 V1 / I1 500 499 498 495 480 405 284 162.9 68.3 34.4 17.21 6.89 3.45 1.722 0.680 0.345 V3 / I1 2.00 1.99 1.98 1.93 1.77 1.71 2.03 3.75 7.06 13.9 34.6 69.1 138 346 691 V1 / IIndicated UL 101-1992, IEC 60990- 1999 I1 V1 C1 R1 uF 0.22 1500 Ω 10 K Ω M V3 500 Ω R2 R3 F 0.022 u C2 Voltmeter Rms reading (UL101) Revised body impedance model Frequency sensitive network for reaction (a) Input impedance (UL 101): Z= V1 / I1 (20 Hz - 1 MHz) Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Peak reading (IEC 60990) (b) Transfer impedance (UL101): Z= V3 / I1 (c) Meter indication (IIndicated): = V3 / R2 = V3 / 500 (weighted mA -IEC 60990; MIU- ANSI C101) (d) Input voltage per mA indication (IEC 60990): V1 / I Indicated (mA)

Touch (Leakage) Current Measurement Instrument for Let-Go 20 50 60 100 200 500 1000 2000 5000 10000 20000 50000 100000 200000 500000 1000000 Freq (Hz) 0.250 0.251 0.253 0.261 0.298 0.348 0.377 0.280 0.164 0.0860 0.0349 0.0175 0.00874 0.00350 0.00175 V3 / V1 2.00 1.99 1.98 1.92 1.68 1.44 1.33 1.79 3.04 5.81 14.3 28.6 57.2 143 286 V1 / IIndicated IEC 60990- 1999 C1 R1 0.22 uF 1500 Ω V1 10 K Ω C2 C3 500 Ω R2 0.0091 R3 uF 0.0062 uF M V3 R4 20 K Ω Voltmeter Body impedance model Frequency sensitive network for Let-Go Frequency sensitive network for reaction Peak reading (IEC 60990) (a) Output voltage to input voltage ratio: Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ V3 / V1 (20 Hz - 1 MHz) (b) Meter indication (scale): IIndicated = V3 (peak) / 500 Weighted mA (c) Input voltage per milliampere indication: V1 / Iindicated (mA)

Touch (Leakage) Current Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Touch (Leakage) Current Topics Definitions (UL101, IEC 60990) Touch current paths Physiological effects of touch current (electric shock) Body impedance models and “safe” voltage limits Touch (Leakage) Current Test Touch current instruments (meters) Measurement circuits and procedures Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Touch (Leakage) Current Test Measurement Circuit Components Power supply Power connections EUT (Equipment Under Test) Measurement Instrument Switching network Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Measurement Equipment Connections

Touch (Leakage) Current Measurement Circuit for 120 Volt Equipment Switching Network UL101 L Polarity reversing switch EQUIPMENT UNDER TEST (EUT) Load S2 Power Supply MEASUREMENT INSTRUMENT A B 120 V S1 A B N GND OPEN Grounded conductor switch INSULATING TABLE Connection to grounded supply conductor Applicable EUT Plug Configurations 15 amp non-polarized N 15 amp polarized 15 amp G N 20 amp G N Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ 2-pole, 2-wire 2-pole, 3-wire

Touch (Leakage) Current Measurement Circuit for 120 Volt Equipment IEC 60990 Optional transformer L EQUIPMENT UNDER TEST (EUT) Load S2 MEASUREMENT INSTRUMENT A B 120 V supply 120 V S1 A B N < 1% line voltage G S3 For 3-wire applications Applicable EUT Plug Configurations 15 amp non-polarized N 15 amp polarized 15 amp G 20 amp G Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ 2-pole, 2-wire 2-pole, 3-wire

Touch (Leakage) Current Measurement circuit for 2- pole 208 or 230-240 Volt equipment suitable for use on 230-240 volt to ground circuit (U.S.Commercial / Industrial) (European 230/400 v residential) 208 or 230-240 V L N Polarity reversing switch EQUIPMENT UNDER TEST (EUT) Load S1 S2 Power Supply MEASUREMENT INSTRUMENT A B A B GND OPEN Line Switch INSULATING TABLE Connection to grounded supply conductor Applicable U.S. EUT Plug Configurations 15 amp G 20 amp G 15 amp 20 amp Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ 2-pole, 3-wire 2-pole, 2-wire

Touch (Leakage) Current Measurement circuit for 2- pole 208 and 240 volt equipment for connection only to 120 volts to ground circuits (120/208, 120/240) (U.S.Residential) L Polarity reversing switch Power Supply EQUIPMENT UNDER TEST (EUT) MEASUREMENT INSTRUMENT S2 120 V A B N 208 or 240 V Load 120 V S1 A B GND OPEN L Line Switch INSULATING TABLE Connection to grounded supply conductor Applicable U.S. EUT Plug Configurations G G Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ 15 amp 20 amp 15 amp 20 amp 2-pole, 3-wire 2-pole, 2-wire

Touch (Leakage) Current Measurement circuit for single phase, 3- pole, 208 or 240 Volt Equipment (e.g., electric ranges, clothes dryers) L Polarity reversing switch GND OPEN EQUIPMENT UNDER TEST (EUT) Power Supply MEASUREMENT INSTRUMENT S2 120 V A B N 208 or 240 V Load S1 120 V A B L INSULATING TABLE Line and Neutral Switch Connection to grounded supply conductor Applicable U.S. EUT Plug Configurations G N G N G N N Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ N 20 amp 30 amp 15 amp 20 amp 30 amp 3-pole, 3-wire 3-pole, 4-wire

Touch (Leakage) Current Touch (Leakage) Current Topics Definitions (UL 101, IEC 60990) Touch current paths Physiological effects of touch current (electric shock) Body impedance models and “safe” voltage limits Touch (Leakage) Current Test Touch current instruments (meters) Measurement circuits and procedures Limits Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Touch (Leakage) Current Test Limits UL 101- 2002 Recommendations Type of appliance Indication in MIU Two-wire cord- and plug- connected appliance 0.50 MIU Three-wire (including grounding conductor) cord- and plug- connected portable appliance 0.50 MIU Three-wire (including grounding conductor) cord- and plug- connected stationary or fixed appliance 0.75 MIU Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ All 70 mA rms (electric burn)

Touch (Leakage) Current SUMMARY Definitions (UL 101, IEC 60990) Touch current paths Physiological effects of touch current (electric shock) Body impedance models and “safe” voltage limits Touch (Leakage) Current Test Touch current instruments (meters) Measurement circuits and procedures Limits Notes:___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Touch (Leakage) Current Questions and Answers

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