High voltage arc resistance test apparatus T4-77

pdfHigh voltage arc resistance test apparatus T4-77



It is constructed in compliance with UL 746A.


T4-77 HIGH VOLTAGE ARC RESISTANCE TEST APPARATUS The purpose of this test is to determine the susceptibility of the test material to resist ignition or form a visible carbonized conducting path over its surface when subjected to high-voltage low-current arcing.

We designed a HIGH VOLTAGE ARC RESISTANCE TEST APPARATUS with the following goals:

  • Reliability
  • Maximum repeatability of test results
  • Maximum comparability of test results
  • Ease of operation
  • Ergonomic design

The BOLD features below are some of the advantages that were introduced to reach these goals.


  • A power transformer rated at 250 VA, primary 120 V ac root-mean-square 60 Hz, secondary open-circuit volts– 5200 V ac rms.
  • A current-limiting resistor bank (with a variable nominal resistance of 2.2 megohms) capable of limiting the short-circuit current at the electrodes to 2.36 mA.
  • Test Electrodes – Both electrodes are to consist of a No. 303 stainless steel rod having a diameter of 3.2 mm (1/8 inch) and an overall length of approximately 102 mm (4 inches). The end is machined to a symmetric conical point having an overall angle of 30 degrees. The radius curvature for the point is not to exceed 0.1 mm at the start of a given test. The electrodes are mounted in a common vertical plane, parallel to the axis of the test sample, orthogonal to one another, and having an angle of 45 degrees to the horizontal. One of the electrodes is fixed and the other located so that there is a spacing across the specimen between the electrodes of 4.0 ±0.1 mm (0.16 ±0.004 inch).
  • Electrodes are easily removable for cleaning, grinding purposes or replacement by thumbscrews. Each electrode is engraved with its serial number to enable its traceability/calibration.
  • Linear drive that moves the movable electrode swiftly towards or away from the stationary electrode depending on the arc condition.
  • Timer – A timer is provided in the test fixture to enable the operator to determine the length of time of the test.
  • Solid anodized aluminum framework with adjustable screw-legs for leveling
  • Electrode holders enable adjustment of all relevant parameters
  • The table for sample positioning is free-standing and enables precise height leveling by thumbscrew. It is removable to enable easy cleaning.
  • Easily removable sample support glass
  • With apparatus are enclosed many different accessories that enable easier testing (see accessories section below)
  • Ventilator for fume extraction after the test
  • Removable bottom lining for easier cleaning
  • Door safety  protection switch - test voltage can only be applied when doors are closed
  • Siemens LOGO programmable microcontroller  or timer
  • Push buttons for switching the voltage ON and OFF
  • Knob for voltage adjustment
  • V meter digital
  • A meter digital 5 A AC ±0,2% +1digit
  • START/STOP push-button
  • Mains switch
  • The anodized aluminum front plate, with inscriptions that clearly explain the function of each component on the front plate
  • Light switch
  • Ventilator switch


 ACCESSORIES (Included in price)

1 pcs.    Glass test platform

1 pcs.    Grinding fixture for grinding of electrodes (they must be ground every couple of tests to keep requested dimensions)

1 pcs.    A grinding platform for forming the electrodes

1 pcs.    Distance gauge - for adjusting the distance between electrodes equipped with its serial number that enables its traceability and certification.


The Control unit is built-in metal sheet housing and consists of all elements needed to control and monitor the electrical parameters of the test.

On the front plate are the following elements: mains switch with fuse and appliance inlet push buttons for switching the voltage ON and OFF (it is only possible to turn on the voltage when the doors of electrode unit are closed), voltage adjustment knob, voltage indication light and instrument, A‑meter, timer or SIEMENS microcontroller, START/STOP push‑button and switches for light and ventilation.




This unit is located on the top of the control unit. All materials used and construction of the complete unit is such that it enables good cleaning. It is equipped with a safety door switch, light, ventilator, and magnet. The electrode mechanism is mounted on the vertical base plate. The complete assembly can be easily taken to pieces for cleaning purposes by enclosed Allen key (Hex wrench). Electrode assembly enables different adjustments that can be performed to meet standard requests. All settings are simple and are done either by thumb-screws or by Allen head screws. Each electrode has an engraved serial number that enables its traceability and certification. It is made of No. 303 stainless steel rod having a diameter of 3.2 mm (1/8 inch) and an overall length of approximately 102 mm. The clamping mechanism of electrodes is so designed that by releasing its thumb screw the electrode can be inserted/removed from it or its position adjusted in a sense of height and alignment of electrode edges to a parallel position.

Electrodes are fixed in holders that enable adjustment of angle and height leveling. Distance between electrodes can be adjusted by thumb-screw and by the help of an enclosed distance gauge. The distance gauge is equipped with its catalog number and serial number that enable its traceability and certification. It is made of stainless steel, handle made of Plastic POM material.

The sample support table is made of anodized aluminum. On top of it is a 5 mm sample support glass plate. The table is equipped with two thumb‑screws. One is for precise height adjustment and the other one for arresting adjusted position. Both table and glass plate are completely removable for cleaning purposes.


Tabletop apparatus: solid case, Non-sensitive, scratch-resistant surfaces through powder-coating, side panels, Al extrusion, RAL 7016, Frame, Al die-cast, RAL 7016, Base and cover, AI, 1.5 mm, RAL 9006, with GND/earthing connection, case feet with an anti-slip protection, front plate and rear panel anodized aluminum 2,5 mm.

Internal and external dimensions in accordance with: IEC 60297-3. Type of protection IP 20 in accordance with IEC 60529, Protective GND/earthing connections in accordance with: IEC 61010, DIN EN 50178 / VDE 0160, DIN EN 60950 / VDE 0805, DIN EN 61010-1 / VDE 0411 part 1, DIN EN 61010-1A2 / VDE 0411 part 1/A1.


On the ceiling of the electrode, the unit is mounted compact industrial aluminum light supplied by safety low voltage. It is equipped with an electronic Lamp-Control Unit for low voltage (24 V DC) and a Compact Lamp (power 11 W, which corresponds to a conventional 75 W filament lamp).

Doors are equipped with a safety switch that disconnects the voltage if the doors are opened. On the back panel is a ventilator/fan for fume extraction.

All parts of the mechanism are nickel-plated, anodized aluminum or made of stainless steel (AISI 304, DIN W. No. 1.4301 X5CrNi18-10) or (AISI 316, DIN W. No. 1.4401 X5CrNiMo17-12-2) http://en.wikipedia.org/wiki/Stainless_steel.


Due to the energy released during the test through the electrodes, their edges do wear out or require cleaning after a certain number of tests. For this reason, we enclose a grinding fixture and grinding platform that enable the user to restore the surface of the electrodes to the original condition maintaining the original angle. After grinding the electrodes shall be inserted in the clamping mechanism and precisely readjusted, and this is best done by the internal light turned on, so that operator can precisely see and carry out all necessary alignments and adjustments.

All components of the electrode unit can be removed and put to pieces, for cleaning procedures. Electrodes, table and glass plate can be removed by means of thumb‑screws, enclosed Allen key, very fast and simple.


Supplying voltage                  220-230V, 50Hz / other optional

Power consumption                   approx. 300VA

 Test voltage:                                   5200 V

 A current-limiting resistor bank, with a variable nominal resistance of 2.2 megohms, capable of limiting the short-circuit current at the electrodes to 2.36 mA.

 V-meter                                  digital, more than 5200 V max.,

A-meter                                   digital, 5 A max., accuracy ±0,2%+1 digit

 Microcontroller                Siemens LOGO or timer

 Ventilator                               dia. 80, 24 V DC

 Light                                        fluorescent 11 W, 24 VDC

 Exhaust tube connection       dia. 80 mm

 Electrodes                            No. 303 stainless steel rod having a diameter of 3.2  mm                                                                                 ( 1/8 inch) and an overall length of approximately 102  mm                                                                           (4 inches). The end  is machined to a symmetric conical point having                                                       an overall angle of 30 degrees

 Linear drive                         for moving the moveable electrode, stroke at least  50                                                                                      mm speed adjustable

SPARE PARTS (can be ordered additionally)


T4-77D           DISTANCE GAUGE


Certificates for voltage, dimensions of electrodes, dimensions of distance gauge, are available on request but are not included in the price.


Warranty: 2 years

Support by E-mail: support@testing.si

On line Skype VIDEO Support: Testing_support, matejsimonic

We will be glad to help you solve your problems and to hear any feedback from you.

The equipment described here is subject to redesign without notice. The change will not impair the function of apparatus its characteristics or the price.