Created by: Glen Zhu | Updated Date: December 13th, 2024
Impulse current generator (8/20µs)
The impact current of 8/20µs can be simulated by a double exponential function. In engineering, the main circuit is often constructed using RLC to generate the impact current.
The Circuit of impulse current generators
Table shows the design of different circuit parameters to generate a 20kA 8/20µs impulse current.
| C/uF | L/uH | R/Ω | U0/kV | Source impedance Rp/Ω |
| 4 | 18.9 | 2.043 | 77.940 | 3.882 |
| 8 | 9.45 | 1.022 | 38.820 | 1.941 |
| 12 | 6.30 | 0.681 | 25.880 | 1.294 |
| 16 | 4.73 | 0.511 | 19.410 | 0.971 |
| 20 | 3.78 | 0.409 | 15.528 | 0.777 |
| 24 | 3.15 | 0.341 | 12.940 | 0.647 |
| 28 | 2.70 | 0.292 | 11.091 | 0.555 |
| 32 | 2.36 | 0.255 | 9.705 | 0.485 |
| 36 | 2.10 | 0.227 | 8.627 | 0.431 |
Therelationship between capacitors and source impedance
Once the charging capacitance C is determined, L and R are determined. U0 only affects the peak discharge current; the larger the capacitance, the smaller the tuning inductance and tuning resistance. When outputting the same impulse current, a lower voltage is required.
The B32K385 residual voltage curve under different impulse currents
The B32K385,s dynamic impedance with impulse current and source impedances
Impulse current generator (10/350µs)
A.Crowbar efficient circuit
When it comes to the zero-crossing point of 0 and nearly 2ms for the tail wave, it exceeds other principle generators by nearly twice. This continuous current will have a serious impact on samples with high dynamic resistance like MOVs. The ball gap arc blowing system needs improvement.
Manufacturers and testing agencies should pay attention to the following points when conducting Class I tests on high-energy MOV chips:
(1) When using Crowbar efficient circuit to test high-energy MOV Class I products, do not judge that the sample’s ability to transfer charge is insufficient based on tail wave losses. In fact, it is due to insufficient load capacity of the testing equipment, which requires either modifying the equipment circuit or replacing a suitable generator.
(2) When using traditional C-RL circuits to test high-energy MOV Class I products, chip breakdown issues often occur in most cases due to excessively long tail wave continuous current. However, this issue should not directly lead to an unsatisfactory test conclusion.
(3) As a third-party laboratory, it is recommended to judge the test samples with the most standard waveform. However, there is no regulation on the zeroing time of the waveform tails in the standards, which is also a controversial issue.
(4) Maintaining technical communication with the inspected unit and conducting reasonable witnessing experiments or comparative experiments are also important means.
Finally, it should be emphasized that while each device meets standards, differences in testing results can be greatly influenced by the operator’s operation, understanding, experience, and even attitude!
Parallel charging, series discharge, output source impedance is related to the capacitance value of the capacitor, discharge tube and surge protective device test: generally 40Ω and 100Ω. High voltage discharge, lightning attachment point test generally approaches high impedance ideal voltage source.
Impulse voltage generator basic circuit
Selection of coupling components
Test purpose:
When the low-voltage distribution system experiences switch operation or faults (such as sudden unloading or single-phase faults) or iron-magnetic resonance effects, harmonics will generate a long-lasting power frequency overvoltage on the SPD, which is called temporary overvoltage. The purpose of this test is to assess whether the SPD can withstand or fail in a non-harmful manner under temporary overvoltage caused by low-voltage system failures.
Test method
(1) Install the SPD according to the manufacturer’s instructions for normal use conditions. Cover all five sides of the test box (except for the mounting surface) with thin paper (thin, soft and with a certain strength paper generally used for wrapping fragile items, weighing between 12g/m2~25g/m2). The size of the test box is usually a cube with each side length of 200~300mm, ensuring that the thin paper is at least 100±20mm away from all directions of the specimen based on actual dimensions of SPD.
Common TOV Test box
| TN Network | TT Network | IT Network | |
| SPD between L-N | 1.32UREF | 1.32UREF | 1.32UREF |
| SPD between L-PE | 1.32UREF | UREF | – |
General situation:
| Allowable AC voltage stress in low-voltage electrical equipment (V) | Cut-off time (S) |
| U0+250V U0+1200V | >5 ≤5 |
GB/T 1689510-2021 Low-voltage electrical apparatus Part 4-44: Safety protection Voltage disturbance and electromagnetic disturbance protection
Schematic diagram of TOV fault
2. The phase wire of armored cable short-circuited with the metal armor due to external force.
Test purpose
In order to check the performance of the internal connections of SPD, to ensure that the internal connections of SPD have the ability to withstand short-circuit currents in fault conditions. If the manufacturer specifies external disconnectors and overcurrent protectors, they should be tested together with SPD to ensure that there is no burning, melting carbonization or spitting out of materials when short-circuit current flows through, causing fires, explosions or flashovers.
Sample preparation
The voltage limiting elements and voltage switch elements (MOV, GDT, gaps etc.) inside the SPD should be replaced with appropriate copper blocks (analogous substitutes) to ensure that the internal connections remain unchanged in terms of cross-sections and surrounding materials (such as resin) and packaging. When non-linear elements are connected in parallel within an SPD, each non-linear element in each current path should be replaced.
This test should be conducted on two different test configurations for each configuration a) and b), using a set of separately prepared samples:
Short circuit module production
Metal screen grid
The metal screen grid should be fixed near the installation on all sides of the SPD, and the minimum distance is specified according to the manufacturer’s claim.
The metal screen grid is a quadrilateral frame, not a box. It should be connected to one tested terminal of SPD through a 6AgL/gG fuse after each short-circuit test. The connection of the grid should be moved to another terminal of SPD.
The screen grid is not covered with thin paper, observe whether the SPD flies to the metal screen grid, causing the 6AgL/gG fuse to blow.
a) Judgment logic for declared short-circuit withstand capability test
Criteria for judgment
(1) There should be no visible damage during the test process. After the test, minor dents or cracks found upon inspection can be ignored if they do not affect direct contact, unless the protection level (IP code) of the SPD is compromised. After the test, there should be no traces of burning on the specimen;
(2) Disconnection should be achieved through one or more internal and/or external disconnectors, and it should be checked whether they provide correct status indication;
(3) For SPDs with a protection level greater than or equal to IP20, a standard test probe applying a force of 5N should not touch live parts, except for live parts that were touched by the SPD before normal installation prior to testing;
(5) If current flows out short-circuit current shall within 5S cut off by one or more internal and/or external disconnectors;
(6) There should be no explosions or other hazards caused to personnel or equipment;
(7) There should be no flashovers on metal screens; gG fuses connecting screens during testing also must not actuate.
b）Low Short-Circuit Current Test
Criteria
(1) There should be no visible damage during the test process. After the test, minor dents or cracks found upon inspection can be ignored if they do not affect direct contact protection, unless the protection level (IP code) of the SPD is compromised. After the test, there should be no traces of burning on the specimen.
(2) For SPDs with a protection level greater than or equal to IP20, a standard test finger should apply a force of 5N without touching live parts, except for live parts that can be touched by normal installation before testing;
(3) There should be no explosions or other hazards to personnel or equipment;
(4) There should be no flashover on metal screens, and the 6AgL/gG fuse connected during testing should not operate.
If there is disconnection during testing, it must also comply with:
(1) Disconnection must be achieved through one or more internal and/or external disconnectors; their correct status indication should be checked;
(3) In case of short-circuit current flowing out from power supply source, it shall cut off within 5S via one or more internal and/or external disconnectors.
The short-circuit current is set to 300A, 45°, and the product disconnects after 1763.1ms.
Test purpose
During normal operation, SPD may fail due to short circuit or open circuit faults. The short-circuit current test is conducted to assess the performance of the internal connections of the SPD by directly replacing the protective components with copper blocks and applying the expected short-circuit current. This test simulates an overvoltage fault added to a normal system operation that causes the SPD to fail. The objective is to determine if the SPD can withstand the expected short-circuit current without causing fires, explosions, arcing, or other accidents.
Sample preparation
For this test, any electronic indicator circuits can be disconnected.
Criteria for judgment
(1) There should be no visible damage during the test process. After the test, minor dents or cracks found upon inspection can be ignored if they do not affect direct contact, unless the protection level (IP code) of the SPD is compromised. There should be no traces of burning on the specimen after testing;
(2) For SPDs with a protection level greater than or equal to IP20, a standard test value should be applied with a force of 5N without touching live parts, except for live parts that were touched by the SPD before normal installation prior to testing;
(3) There should be no explosions or other hazards caused to personnel or equipment;
(4) There should be no flashover on metal screens, and during testing, the 6AgL/gG fuse connected to the screen should not operate.
(5) Disconnection should be achieved through one or more internal and/or external disconnectors; their correct status indication must be checked;
Single chip pressure sensitive tolerance qualified demonstration
Three pieces of non-conforming pressure-sensitive demonstrations
(1) When the declared value of the pre-treatment short-circuit current is large, for example 20A, for varistor products in the pre-treatment stage, short-circuit failure will occur within 5s. If it is a qualified product, timely disconnection through external/internal disconnectors within 5s without any danger such as fire or explosion will occur.
(2) When the declared value of the pre-treatment short-circuit current is small, for example 1~2A, during the pre-treatment stage, products may not be fully activated and with a small short-circuit circuit, even inferior varistor products will not experience phenomena such as fire. Therefore, it is recommended that manufacturers increase the declared value of the pre-treatment short-circuit current and use more stringent test levels to ensure product quality.
(3) The expected short-circuit current value claimed by the manufacturer in the SPD short-circuit test should be carefully considered. If the claimed value is too high, for example, above 300A, the probability of passing the short-circuit current characteristic test will be higher. This is because internal connecting components are more likely to disconnect within 5 seconds due to excessive current. However, for simulated SPD failure tests, if the SPD does not completely trip during the pre-processing stage and is subjected to subsequent reference voltage effects, a high expected short-circuit current will increase the probability of SPD ignition and combustion. Therefore, the expected short-circuit current value should be a compromise in order to ensure that both tests can be passed.
(4) When conducting this test on switch-type products, it is generally unlikely to see a phenomenon similar to the ignition and combustion of MOV valve pieces. The product may not turn on or may frequently short circuit or open circuit with the periodic variation of AC voltage.
Equipment name | Parameter requirements |
Impact current generator
| 10/350µs: Iimp tolerance ±10%, charge quantity Q tolerance -10%/+20%, specific energy tolerance -10%/+45%; 8/20µs: Peak value tolerance ±10%, front time tolerance ±10%, half peak time tolerance ±10%, overshoot or oscillation amplitude not greater than 5% of peak value, reverse peak current value not greater than 30% of peak value. |
Surge voltage generator | 1.2/50µs: Peak deviation ±5%, front time deviation ±30%, half peak time deviation ±20%, amplitude of the rising part from 0% to 80% of the peak value of the impulse voltage not greater than 3% of the peak value, generator short-circuit current less than 20%In |
Compound wave generator (with even-odd network) | 1. 2/50µs: Peak deviation 20kV±5%, front time deviation ±30%, half peak time deviation ±20%, amplitude of the rising part of the impulse voltage peak from 0% to 80% not greater than 3% of the peak value, short-circuit current of generator less than 20% In; 8/20µs: Peak deviation 10kA±10%, front time deviation ±10%, half peak time deviation ±10%, overshoot or oscillation amplitude not greater than 5% of the peak value, reverse peak current value not greater than 30% of the peak value, virtual impedance is 2Ω |
Measurement system (oscilloscope, Rogowski coil, voltage divider, etc.) | Current: accuracy within ±3%; Voltage: accuracy within ±3%; Bandwidth at least 25MHz, overshoot less than 3%; |
Standard trial production, electrical indicator, push-pull force gauge
| Articulated probe: diameter 12mm, length 80mm; spherical probe: diameter 12.5mm Voltage: AC 40~50V Thrust: range 50N, graduation value 0.25N |
Test connection method:
Line length | terminal block | 9cm lead wire | 100cm lead wire |
current/kA | 19.64 | 19.79 | 18.56 |
Residual pressure/kV | 1.57 | 1.63 | 1.69 |
The use of longer low-voltage end leads to a measured residual voltage value that is 120V higher.
Connection method | Not twisted pair | Twisted pair |
current/kA | 19.54 | 19.64 |
Residual pressure/kV | 1.64 | 1.57 |
The double twisting caused the measured residual voltage to be 70V higher.
Reasons for different residual voltage curves:
In general, the interference of discharge current can be eliminated by adjusting the spatial position and direction of the voltage divider.
Method for determining limiting voltage:
Criteria for data results:
For example, if a laboratory’s extended uncertainty for limiting voltage projects is 70.0V (with a probability of 95% and k=2), and if a sample’s Up value is 1.8kV, when measuring result shows up as 1.75kV – even though exceeding Up when including extended uncertainties – since actual measurement doesn’t surpass Up directly; therefore deemed qualified.
Equipment name | Parameter requirements |
Impact current generator | 10/350µs: Iimp tolerance ±10%, charge quantity Q tolerance -10%/+20%, specific energy tolerance -10%/+45%; 8/20µs: Peak value tolerance ±10%, front time tolerance ±10%, half peak time tolerance ±10%, overshoot or oscillation amplitude not greater than 5% of peak value, reverse peak current value not greater than 30% of peak value. |
Impedance current tester/power meter/clamp ammeter | Current: Range 0-20mA, resolution not exceeding 0.1mA; Voltage: AC 0-1000V, error within ±3% |
Compound wave generator (with even-odd network)
| 1. 2/50µs: Peak deviation 20kV±5%, front time deviation ±30%, half peak time deviation ±20%, amplitude of the rising part from 0% to 80% of the peak value not greater than 3% of the peak value, short-circuit current of generator less than 20% In; 8/20µs: Peak deviation 10kA±10%, front time deviation ±10%, half peak time deviation ±10%, overshoot or oscillation amplitude not greater than 5% of the peak value, reverse peak current value not greater than 30% of the peak value, virtual impedance is 2Ω |
Measurement system (oscilloscope, Rogowski coil, voltage divider, etc.) | Current: Accuracy within ±3%; Voltage: Accuracy within ±3%; Bandwidth at least 25MHz, overshoot less than 3%; |
Standard trial production, electrical indicator, push-pull force gauge | Articulated probe: diameter 12mm, length 80mm; spherical probe: diameter 12.5mm Voltage: AC 40~50V Thrust: range 50N, graduation value 0.25N |
The experiment should use another test sample, connected to the test sample cabinet of the 8/20μs impulse current generator, select the impulse resistance-capacitance divider, and the coil testing the continuous flow peak value should be connected in series with the circuit on both sides of the test sample and power supply.
Due to the long tail truncation time of the 10/350µs waveform, the duration of the follow current cutoff in the figure is 18.70ms, much higher than the duration of triggering follow current at 8/20µs.
Key points for testing:
Equipment name | Parameter requirements |
Electric traceability test equipment | Electrode: Platinum metal with a minimum purity of 99% should be used for the electrodes. The two electrodes should have a rectangular cross-section of (5.0±0.1) mm x (12.0±0.1) mm, with a -30±2 slope. The two electrode faces should be perpendicular to each other, with an angle between the electrodes of 60±5 degrees. The distance between the electrodes should be 4.0±0.1mm, and the force applied to the surface of the specimen for each electrode should be 1.00±0.05 N. Dielectric withstand test equipment test circuit: The sinusoidal voltage should vary from 100 to 600V, with a frequency of 48-62Hz. The maximum error of the voltage device is 1.5%, and the power supply power should not be less than 0..6kVA.The short-circuit current between the two electrodes should be able to reach 1..0 ± .01A, and at this current level, voltage drop shouldn’t exceed10%.The maximum error in short-circuit current is ±3%. Drip device: Test solution droplets should occur at intervals of30 ± .05s, with a drip height of35 ± .05mm,and target time between drops being30s. Specimen support platform: One or more appropriately sized glass plates with a total thickness not less than4mm. |
Electronic balance | Weight: 0~500g, accuracy 0.01g |
conductivity meter | Conductivity: 0.00~100.0mS/cm, error ±1%; Temperature: 0~99.9℃, error ±0.4℃ |
Experimental Purpose:
The electrical erosion test is an important method to evaluate the corrosion resistance of insulation materials, and it is an important basis for determining whether materials can be used in harsh environments. It is particularly important to correctly measure the Comparative Tracking Index (CTI) and Proof Tracking Index (PTI) of insulation materials.
Preparation of Test Samples:
Size and shape of test samples: The sample surface should be flat, smooth, and scratch-free. The surface area should prevent liquid from flowing out from the edges during testing. The size should not be less than 20mm x 20mm, with a thickness of 3mm or more. Multiple material samples can overlap to achieve a minimum thickness of at least 3 mm.
Preparation of Test Solution:
Use deionized water, ammonium chloride powder, conductivity tester and electronic balance to prepare the test solution A: Analytical pure anhydrous ammonium chloride (NH4Cl) reagent with a mass fraction of about 0.1% and a purity not less than 99.8% is dissolved in deionized water. The resistivity of the solution at 23±1℃ is 3.95±0.05 Ω.m, at 25℃ it is 3.75±0.05 Ω*m, and at 20℃ it is 4.25±0.05 Ωm.
Preparation for Equipment Calibration:
(1) Electrode and droplet device adjustment: Adjust the X-axis moving table and Y-axis moving table, place the glass on the lifting platform, then place the sample on the glass, adjust the lifting platform to make two electrode arms form a horizontal line, so that each electrode arm exerts a force of 1.00±0.05N on the sample, with a distance between two electrodes of 4.0±0.1mm; adjust the two knobs behind the droplet mechanism to move it up and down, so that the needle tip of the syringe is 35±5 mm away from the upper surface of the sample.
(2) Leakage mark drop liquid adjustment: Pour a suitable amount of deionized water into the dropper cup, press the “drain” button on the panel to remove air from the needle. Pour the prepared solution into the dropper cup, press the “drop” button, observe if there are any drops that have not fallen or if more than one drop falls at once. Start the experiment after normal dripping of drops.
(3) Short circuit debugging: Adjust the required test voltage value, then rotate the current adjustment knob, press the “electrode short circuit” button to make the short-circuit current 1.0±0.1A. At this current, the voltage drop indicated on the voltmeter should not exceed 10%. The maximum error of the measurement device for short-circuit current value is ±3%.
Test method:
The withstand voltage value depends on the measured creepage distance value and the corresponding material group category. If the corresponding material group category is not qualified, reduce one category for further testing until the lowest category of materials. For example, if a product’s U is 385V and the minimum measured creepage distance is 3.0 mm, according to Table 5.19 SPD creepage distance, meeting material group categories II or above, then select a withstand voltage value of 400V with 50 drops of liquid. If this test level cannot pass, then the corresponding creepage distance is also deemed unqualified and continue to do the next test level at 175V with 50 drops.
Key points of testing:
(1) The surface of the sample should be clean without dust, dirt, fingerprints, grease, oil release agents or other contaminants that may affect test results. When cleaning samples, care should be taken to avoid causing swelling, softening or substantial abrasions that could damage materials. Among common contaminants on sample surfaces are dust and fingerprints. Dust can be removed directly with distilled water while fingerprints mainly consist of water, inorganic salts and fatty oils which are difficult to detect but easily affect test results; they can be cleaned using an alcohol solution around 20% concentration followed by rinsing with distilled or deionized water to effectively remove contaminants from sample surfaces without affecting test results.
(2) The thickness of samples must not be less than 3mm because typically under samples there are glass or steel plates as pads; during tests chloride ammonium ion solutions generate a lot of heat so if samples need to endure heat but are too thin it will quickly dissipate heat preventing them from enduring chloride ammonium ion solutions’ effects thus ensuring sample thickness no less than 3mm during tests or stacking same-material samples together so their combined thickness exceeds at least over three millimeters while stacked sample sizes should ideally match each other.
(3) Analytical grade (denoted by letter AR) anhydrous ammonium chloride purity must not fall below 99.5%; generally only reagent grade (denoted by letter GR) achieves purity levels exceeding at least over ninety-nine point eight percent; solvents when unopened have shelf lives around five years but once opened require sealing storage shortening shelf life down two years; if solvent used in tests has solidified it needs drying in oven before use preventing moisture within solvent affecting final solution preparation process.
(4) The conductivity of distilled water and deionized water is very low, indicating that they contain very few impurities. When the conductivity is low to a certain extent, the influence of impurities on the solution can be ignored. If the conductivity is too high, the relative content of impurities increases, significantly affecting the electrolysis of NH4Cl in the solution and thus affecting experimental results.
(5) The resistivity of a solution is an important factor influencing the results of electrical traceability tests. Solutions should be prepared according to the requirements for resistivity, with mass fraction only serving as a reference. It is best to prepare and use solutions immediately without storing them for too long. For example, if a solution is stored for an extended period in equipment prone to leakage currents, there may be a decrease in resistivity at the bottom of the solution. If storage is necessary, it should be sealed and kept in a cool place; when using it again, measure its resistivity to ensure it meets standard requirements.
(6) Temperature has a significant impact on the conductivity value of electrolytes. The conductivity value of electrolytes at specific concentrations changes with temperature variations. As temperature increases, electrolyte conductance enhances leading to lower resistance values and higher conductivity values. Standards specify that measurements for test solutions’ conductivity must be conducted at 23±1 ℃; before measuring electrolyte conductance, allow sufficient time for solutions to reach room temperature (23±1℃). Use either a thermometer or a conductance meter equipped with temperature sensors during measurement processes so that you can control your measured electrolyte’s temperature within 23±1℃ as per standards specified regulations.
(7) When the two electrodes are not perpendicular to the surface of the sample, that is, when the electrodes do not have good contact with the sample surface, it will seriously affect the test results. In addition, after multiple tests and combustion of the sample, there may be carbonization melting on the surface of platinum electrodes. If this electrode continues to be used for testing, carbides will form a barrier layer between the electrode and sample, affecting their contact. Therefore, in order to obtain more accurate test results, pay attention to observing the condition of the electrode after each test. If necessary, use fine sandpaper labeled 400 to polish the electrode carefully without changing its contour or turning its edge into a cylindrical shape; otherwise incomplete contact between electrode and sample may occur. After polishing is completed, rinse off with deionized water or distilled water.
(8) Each test voltage should have a separately set short-circuit current value. For different test voltages: if only one short-circuit current value is set (e.g., 1A for a 200V test voltage), then increasing it to 300V might result in exceeding 1A; conversely decreasing it to 150V might result in less than 1A. To ensure compliance with standards requirements during testing adjustments in voltage should always be accompanied by corresponding adjustments in short-circuit current.
(9) After each test – regardless of success or failure – solution splashes into equipment are likely as well as ash from burnt samples scattering onto armrests which could fall onto future samples affecting results negatively. Thus cleaning both electrodes and support devices post-test is essential using non-corrosive cleaners like alcohol followed by rinsing with deionized or distilled water while also cleaning droplet devices thoroughly afterwards.
(10) If the crawling distance is greater than or equal to twice the specified value in Table 5.19, or if the insulation material is made of ceramics, mica, or similar materials, no test is required.
(11) If multiple tests are performed on the same sample, there must be sufficient spacing between test points to prevent contamination of other surfaces being tested by splashing dirt from test points.
(12) During testing, it may be encountered that electrolyte or contaminants accumulate in pits or defects on the surface of the sample, causing the action of overcurrent relays rather than leakage current traces. In this case, the test must be redone.
Table Crawling distance of SPD Unit: mm
| Voltageb，c RMS/V | Printed circuit board material pollution level | Pollution level | |||||||
| 1 | 2 | 1 | 2 | 3 | |||||
| All materials group | Material group excluding IIIb | All materials group | Material group a | Material group a | |||||
| I | II | III | I | II | IIId | ||||
| 10 | 0.025 | 0.4 | 0.08 | 0.4 | 0.4 | 0.4 | 1 | 1 | 1 |
| 12.5 | 0.025 | 0.4 | 0.09 | 0.42 | 0.42 | 0.42 | 1.0 | 1.05 | 1.05 |
| 16 | 0.025 | 0.4 | 0.1 | 0.45 | 0.45 | 0.45 | 1.1 | 1.1 | 1.1 |
| 20 | 0.025 | 0.4 | 0.11 | 0.48 | 0.48 | 0.48 | 1.2 | 1.2 | 1.2 |
| 25 | 0.025 | 0.4 | 0.125 | 0.5 | 0.5 | 0.5 | 1.2 | 1.25 | 1.25 |
Definition analysis:
(1) Comparative Tracking Index (CTI): The maximum voltage value at which 5 samples do not exhibit tracking failure or sustained burning during the application of 50 drops of liquid, such as PTI175.
(2) Comparative Tracking Index (CTI): The maximum voltage value at which 5 samples do not exhibit tracking failure or sustained burning during the application of 50 drops of liquid, also including a description of material performance during a test with 100 drops, indicated as CTI250 or CTI250 (200).
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