Archive for September, 2012

Questions and Answers on Grounding Test, Voltage Proof Test and Leakage Current Test

Posted on September 17, 2012  by Xixi  in Importing from China, Quality Control   No Comments »
Questions and Answers on Grounding Test, Voltage Proof Test and Leakage Current Test

[Original] Why is it necessary to conduct the grounding resistance test?

It is also known as grounding continuity test. The test should be conducted on all class I products. The purpose for the test is to ensure all conducting components of the product which can be touched by users and will turn to charged body when the single insulation is failure are connected to the ground point of the power input. In other words, a grounding test is to verify the integrity of the grounding path by connecting a high current low-voltage power supply to the ground loop.

To judge if the product complies with the standard and requirement, the protective impedance between the grounding connection terminals or grounding contact and the components should be measured. It is considered complying with the requirement if the impedance does not exceed a fixed value which is determined by the product safety standards. Be sure to remember, from the structure and design point of view, the conductor which is used for protecting grounding should not contain any switches or fuses.

Test requirements:

Most of the standards have parameter requests for grounding test.

· The EUT must be under the high DC or AC but low voltage for a certain period of time.

· The potential fall between the grounding connection terminals or grounding contact and the components must be measured

· The resistance value must be calculated by current value flowing through it and the potential fall generated.

The impedance should be no more than a certain value which is different in different safety standards. For example, the test voltage is required no more than 12V in IEC 60950-1. The current can be AC or DC, and the current value should be 1.5 times the rated current of the product or25A(choose the bigger one). The test duration must be exactly 1 minute and the protective impedance between the grounding connection terminals or grounding contact and the components that should be earthed must be no more than 0.1? (not including the impedance of the cables). In some standards, such as CAN/CSA-C22.2 No. 60950-1 or UL 60950-1 (including the difference of Canada), if the rated current of the product is no more than16A, the test current should be40Aand the test duration should be 2 minutes.

In most standards except the Canadian standard, the test current is required less than25Aand the duration is 1 minute which means the biggest current and longest operating time can be stood by the overcurrent protective device. The maximum current value,25A, is 1.5 times the rated value of most wires connect to the setup switches of the inserted type A devices, which is no more than16A. The requirements of Canadian National Wiring Code are very similar to the above requirements. They assume that the lifetime of the fuses is no more than 1 minute when it is under 2 times the rated current value. It is said in the UL standard that the fault current will be40Aand the duration is no more than 2 minutes because of the use of20Aline switching protection in most power circuits.

[Original] Why is it necessary to conduct the voltage proof test? (Part I)

Dielectric strength test, also known as hipot, is probably the most well-known production line safe test and is performed frequently, which suggest that it is an important part in every standard actually. Hipot is a nondestructive testing, whose purpose is to confirm that electronic insulation materials can resist instant High voltage. It is a high voltage test which is used for all devices to make sure that the insulating material is sufficient. Another reason of hipot is that it can find out the probable flaw such as the insufficient of leakage distance and clearance caused in manufacturing process.

In type tests, hipot is done after other tests (such as failure test, dampness test or vibration test) to examine whether there is insulation deterioration caused by those tests. However, the hipot in current production is a kind of test in manufacturing process to make sure that the structure of the product is the same as the one used in the type tests. Some flaw caused in manufacturing process can be found out in the on-line hipot, such as the diminishment of the clearance and the creepage distance of transformer winding. Such kind of failure may caused by a new operator in winding department. Other examples include examining the pinhole flaw of insulation materials or finding an oversize soldering point.

Most safety standards use the convention of 2xU + 1000 V as the basis of insulation material test. The U here means operating voltage (value rms). The convention is just a guide to provide a detailed form to individual standards especially IEC 60950. This form is used for defining how to confirm a certain test voltage according to the voltage measured in actual operation. The reason of using 1000V as fundamental convention is because it is the affordable transient over-voltage of the insulation material in daily use. Experiment and research show that the voltage at these circumstances is usually ran up to 1000V.

Test Method:

High voltage is usually used in the two components over the insulation material under test, such as the primary circuit and the metal shell of the EUT. If the insulation material between the two components is enough, the high voltage between the two components separated by the insulation material can generate very little current flowing through the insulation material. Though the small current is acceptable, breakdown should not occur to the air insulation or solid insulation. Therefore, it should be noted that this current is caused by partial discharge or breakdown, but not caused by capacity connection.

Another example is the test of the insulation material of the power supply between the primary and secondary circuit. At this time, all outputs short together. The ground probe of the hipot tester connects with the outputs and the HV probe connects with L and N (L and N are shortened). (See also picture 1) the EUT should not work when it is under a hipot. There is one thing should be noted. In the period of the type tests, the ideal condition is that the voltage should be less than 1/2 rated voltage at the beginning, following by gradually increase till it reach the rated voltage in 10 seconds, and that should last for 1 minutes. However, for most test instruments, the rated voltage is output directly or reached step by step by using an electronic control circuitry.

The picture is as follows:

Picture1. Connection diagram of type tests

Test duration:

If the test is one part of the certification process, the test duration must in accordance with the safety standards. For example, in most standards, including IEC 60950, the test duration is 1 minute. However, when the test is under test in the production line, it is unpractical to conduct a hipot on every product for 1 minute. The producer will always shorten the test duration, like several seconds, but use higher voltage instead. A typical empirical rule for this is 110-120% (2xU+1000 V), 1-2 seconds. The test duration and procedures should be approved by the related testing agency. It is worth be noted that every insulation material has its own specific voltage duration according to tests and the data of producer, though the time shortened is about the same as the voltage increased.

[Original] Why is it necessary to conduct the insulation resistance Test?

The insulation resistance test is also known as Megger test. The purpose is to measure the total resistance between the two spots that are separated by insulation materials. Therefore, the test can confirm how much effectiveness is made when the insulation resistance resists the flowing current. The current is very low, because the voltage in the test is usually 500~1000Vdc. Because of the low current, the test is useful to examine the quality of the insulation materials, not only when the products are being produced, but also when they are in use.

Test procedures: EUT

To connect it to the tester and make the test voltage increase from 0 to the maximum value (usually 500 V dc). At the moment the voltage reaches the maximum value, keep that value for a while (usually 5 seconds), and then record the resistance value. The measured value should be very high (usually in the teraohm level). The measure of insulation resistance is a mandatory requirement in some standards, such as IEC60950-1 and UL6500.

[Original] Why is it necessary to conduct the Voltage Proof Test? (Part II)

Current setting:

Nowadays, most hipot testers allow the users to set the limit value of the current. However, if the actual leakage current is known, the test current of hipot is predictable. The selection of the limit value is in accordance with the products under test. The best way to select limit value is to work out an average current by making hipots on some product samples. The limit value of the leakage current is set to a higher value than the average one. The other method to set limit current value is to use the following mathematical formula:

The picture is as follows:

The reason why using 2 as the factor is that the leakage current of the circuit is produced by a capacity Y, but the leakage current of the hipot is produced by the capacities of every circuits together. You can predict the hipot current by deriving the equation of I (hipot). Therefore, the limit current of the hipot tester should be set high enough to avoid the misjudgment caused by the existence of the leakage current, but not too high to examine the breakdown of real insulation materials.

Most standards allow using AC or DC to make a hipot. When AC voltage is used in the test, the voltage stood by the insulation materials under test is the peak value. Therefore, if you decide to use DC for test, you must make sure that the DC test voltage is Ö2 times (or 1.414 times) the AC test voltage. In this way, the peak values of both the DC and AC voltage are the same. For example, if the voltage value is 1500 V AC, the equivalent DC voltage value for insulation test should be 1500 x 1.414 or2121 V DC.

An advantage of using DC voltage for test is that the limit leakage current can be set to a lower value than using AC voltage instead. In this way, there are greater chances for the producer to find out the products whose insulation materials are losing effectiveness. These products may probably pass the AC voltage test. It must be noted that the capacitors in the circuit are highly charged when AC hipot tester is used. Therefore, it is necessary to use a safety discharge equipment and set it correctly. However, no matter which kind of voltage is used, it is a good way to discharge the product before it can be touched by people.

Another advantage of the DC hipot tester is that its voltage increases gradually. The operator can find out the potential failure of the insulation materials before by monitoring the current changes when the voltage increases. A little weakness of the DC hipot tester is that its cost is a little higher than an AC hipot tester, for the former more difficult to produce.

There is a little abuse of the AC hipot tester. If there are large-capacity capacitors Y in the circuit under test, the AC tester may tell a failure because of the setting of the limit current of the hipot tester, but the insulation materials have no breakdown. Most standards allow users to test with the capacitor Y cut off or to use the DC hipot tester. The DC hipot tester will not tell a failure because of the existence of the large-capacity capacitors Y, because the current will not flow through the capacitor Y under DC voltage.

[Original] Why is it necessary to conduct the Leakage Current Test?

In some standards, including IEC60950-1, leakage current is named as touch current. In other words, it is the current flowing through human bodies or animal bodies when a person or an animal touches a touchable part of a device. There is another conception called protective conductor current, which is equal to the current flowing through the protective conductor. Therefore, protective conductor current has never been the reason causing electric shock because protective conductor is always connected to the ground according to the definition.

If the contact current is too high, the operator will be shocked, and that may lead to serious damages which are related to the operator’s weight. Usually, if the current is more than 1.0mA and flows through human body, it can cause electric shock damage. The extent of damage is related to the current value and the person’s weight.

Similar to other tests, leakage current test is another important part of the safety tests. In most safety tests, the test should be under different conditions, such as normal operating condition, switch on and off, and exchange of the power cord polarity. The earth leakage current should be no more than the limitation under any conditions. Table I lists part of the usual limit.?IEC60950-1, Table 5A?

The picture is as follows:

 

The biggest contributor of leakage current is the capacity over the live wire and the ground, such as capacity Y. The capacity Y is usually added into the circuit in order to control EMI. It must be noted that in some standards, such as IEC60950-1, the earth leakage current of class I vertical devices is allowed to exceed 3.5mA if it meets the conditions in section5.1.7of IEC60950-1 at the same time.

In the leakage current test of the IT equipments, it must be noted that the tester should be in accordance of the requirements in appendix D of IEC60950-1. This test makes a network simulation of the worst situation of body resistance. It is strongly recommended to use an isolating transformer for the test.

The picture is as follows:

Any capacitive leakage current of the transformer must be considered. If it is for some reason impossible to use an isolating transformer, the EUT must be fixed on an insulating desk and appropriated safety warning should be posted. This kind of measurement is a make-up for the possibility of the dangerous voltage carried by the EUT.

Test Method:

Most standards, especially IEC0950, require the EUT to be in the state of power-on. The supply voltage of the EUT is 110% of the upper limit of the rated value and the frequency is the maximum rated frequency. As previously mentioned, for the sake of safety, it is strongly recommended to use an isolating transformer for the test.

These tests can be done for both class I and class II. For class II, the touchable conductive components and metal shell should be tested. You can touch the shell surface with metallic film (10*20cm) which imitating human hands.

This test can be also done under any conditions, such as normal operating condition, switch on and off, and exchange of the power cord polarity. The devices which include multi power input must be tested with only one power on if they are required to be used with one power on each time (such as back source). Though most standards do not require a 100% leakage current test on the production line, some special standards, such as those for medical instruments, ask for a 100% test.

Test Item of CE Product

Posted on September 14, 2012  by Xixi  in Importing from China, Quality Control   No Comments »
Test Item of CE Product


1. Input Test:

Test the power, the rotating speed (RPM), voltage of motor, current of motor and air volume (L/S) at different gears. Check if the heating wires become red.

 

2. Insulation Withstand Voltage Test

Cover the sample’s surface with metal leaf. Input the voltage of 3,750V between the metal leaf and the plug of the power cord for 1 minute. The leakage current should be no more than 0.5MA.

Demand:

there should be no electric leakage.

 

3. Abnormal Operation Test No.1

Test method:

  1. Separate the two stages of the motor and the circuit of the product. Connect the other motor to the circuit.
  2. Connect the motor to a separate power supply. The voltage should be 0.94 time the rated voltage when the motor works.
  3. Connect the motor to the working power supply. Adjust the voltage to make the power 0.85 time of the rated power.
  4. Put the sample in the test corner. After working for 30 minutes, measure the temperature of each spot.

Demand:

The sample should not burn or smoke. The cover should not melt.

Test result:

Measure the internal lead, air outlet, diode, capacity, the soldering point of the power cord, the surface of the power cord, the shell of the switch, the point on the surface of the front shell which is 1/2’’ far away from the air outlet and the temperature of the three points in the corner.

 

4. Abnormal Operation Test No.2

Test method:

  1. Separate the two stages of the motor and the circuit of the product. Connect the other motor to the circuit.
  2. Connect the motor to a separate power supply. The voltage should be 0.94 time the rated voltage when the motor works.
  3. Connect the motor to the working power supply. Adjust the voltage to make the power 1.24 time of the rated power.
  4. Put the sample in the test corner. After working for 30 minutes, measure the temperature of each spot.

Demand:

The sample should not burn or smoke. The cover should not melt.

Test result:

Measure the internal lead, air outlet, diode, capacity, the soldering point of the power cord, the surface of the power cord, the shell of the switch, the point on the surface of the front shell which is 1/2’’ far away from the air outlet and the temperature of the three points in the corner.

 

5. Abnormal Operation Test No.3

Test method:

  1. Separate the two stages of the motor and the circuit of the product. Connect the other motor to the circuit.
  2. Connect the motor to a separate power supply. The voltage should be 0.94 time the rated voltage when the motor works.
  3. Put the sample in the test corner. After working for 30 minutes, do the insulation test.  (3750V,1MIN,0.5MA)

Demand:

The sample should not burn or smoke. The cover should not melt. The HI-POT should be successful.

 

6. 7cm Wind Blocking Test

Test method:

  1. Connect the sample to the supply. Adjust the voltage to make it 1.24 time of the rated voltage. The distance between the air outlet of the sample and the wall is 7cm.
  2. Make the sample work for 15 minutes then turn off it. After one minute, observe the tripping switch.

Demand:

The tripping switch should not break off in the whole process of the test.

 

7. Components Temperature Test

Test method:

Connect the sample to the supply. Adjust the voltage to make the power 1.24 time of the rated power. After working for 30 minutes, measure the temperature of each spot.

Test result:

Measure the internal lead, air outlet, diode, capacity, the soldering point of the power cord, the surface of the power cord, the shell of the switch, the point on the surface of the front shell which is 1/2’’ far away from the air outlet and the temperature of the three points in the corner.

 

8. Motor Deceleration Test

Test method:

  1. Separate the motor and the circuit of the product. Connect the other motor to the circuit.
  2. Connect the motor to a separate power supply. The voltage should be the voltage when the motor works at rated power
  3. Connect the motor to the working power supply. Adjust the voltage to make the power 1.15 time of the rated power.
  4. After working for 10 minutes, the voltage should be reduced at the rate of 1V per minute till the switch tripped.
  5. Increase the motor’s voltage at the rate of 1V per minute till the tripping stops. After working for 30 minutes, measure the temperature of each spot.
  6. After the sample cools down, do the insulation test. (3750V, 1MIN, 0.5MA)

Test demand:

In the whole test process, the sample should not burn or smoke and the cover should not melt.

Test result:

Test the power, the voltage when the motor starts, the voltage of the motor when the switch trips, the voltage when the motor stops, the insulation, the withstand voltage, the condition of the sample.

 

9. Power Cord Tensile Test

Test method:

  1. Hang heavy objects of 6.7 pound on the power cord of the sample.
  2. Lift the sample with the heavy objects in the most devastating direction and put the heavy objects on the ground. The whole process takes 1 second.
  3. Repeat the test for 25 cycles.
  4. Measure the length of the cord which is pulled out and observe the assembling of the power cord.

Demand:

Towed length of power cord should be no more than 2mm.

 

10. Air Inlet Coverage Test

Test method:

Connect the sample to the rated voltage. Plug the air inlet with poly-bag till the tripping switch is off.

Test requirement:

During the test, the product should not melt, burn or smoke. The functions of sample are normal.

 

11. Air Outlet Coverage Test

Test method:

Connect the sample to the rated voltage. Plug the air outlet with poly-bag till the tripping switch is off.

Test demand:

During the test, the product should not melt, burn or smoke. The functions of sample are normal.

 

12. Overload Test

Test method:

  1. Switch on the sample and adjust the voltage to make the power meat the following requirements: If the rated power is less than or equal to 100W, it is 1.33 times the rated power. If the rated power is more than 100W but less than or equal to 200W, it is 12W more than 1.21 times the rated power. If the rated power is more than 200W, it is 1.27time of the rated power.
  2. The whole process of the test is 15 cycles. For the hairpin type products, working for 60 minutes and shutdown for 30 minutes is called a cycle. For the wind-cone products, working for 30 minutes and shutdown for 30 minutes is called a cycle.
  3. After the above test, do the insulation withstand voltage test. (3750V, 1MIN, 0.5MA)

Test requirement:

During the test, the product should not melt, burn or smoke. HI-POT test should not fail.

 

13. Life Test

Test method:

1. Make the sample work at 1.1 times the rated voltage for 48 hours continuously.

2. Make the sample work at 0.9 times the rated voltage for 48 hours continuously.

Test requirement:

During the test, the product should not melt, burn or smoke. The functions of the sample are normal after the test.

 

Engineering Design Validation Report of Engineering Department

 

1. Input Power Test:

Test the power, the rotational speed, wind velocity, motor voltage, and motor electric current; observe whether the heat wear turns red

 

2. Insulation Test:

Turn on the switch at the highest level. Cover the sample’s surface with metal leaf. Input high voltage between the metal leaf and the plug of the power cord for 1 minute. The value of the voltage is as following: single insulation, 1000V; Double insulation, 3750V.

Demand:

The leakage current is no more than 0.5mA.

 

3. Air Inlet Coverage Test:

Test method:

Connect the sample to the rated voltage. Plug the air inlet with poly-bag till the tripping switch is off. Record the time when the switch trips.

Test requirement:

During the test, the product should not melt, burn or smoke. If there is a fuse, it should not be broken. The functions of the sample are normal after the test.

 

4. Air Outlet Coverage Test:

Test method:

Connect the sample to the rated voltage. Plug the air outlet with poly-bag till the tripping switch is off. Record the time when the switch trips.

Test requirement:

During the test, the product should not melt, burn or smoke. If there is a fuse, it should not be broken. The functions of the sample are normal after the test.

 

5. One Machine Drop Test:

Test method:

  1. Turn on the switch of the sample at the biggest level to make it work at the rated voltage. (If the sample is hair pliers’ type, make it work for 2 hours, then do the following test.)
  2. Make the sample fall on the hard board from three different directions at the height of 3 inches.
  3. Examine the sample to make sure it is in accordance of the test requirements.
  4. The height which the sample falls off is 6 inches; repeat the procedures 2 and 3.

Test requirement:

  1. After the test, the functions of the sample are normal. There is no damage or crack of the components.
  2. In the whole testing process, insulation should not break or burn and the electrified body should not be touched by the test finger.

 

6. Power Cord Tensile Test:

 

Test Item of UL Product

Posted on September 13, 2012  by Xixi  in Importing from China, Quality Control   No Comments »
Test Item of UL Product

1. Cover Strength Test

Test method: Press the product at the position of air inlet and the air outlet vertically with a test finger whose diameter is 6.4mm*127mm. The force of the pressure should be 5 pounds and should last for one minute.

Demand:

During the test, the uninsulated electrified parts should not be touched by the test finger; after the test, the distance between the uninsulated electrified parts should not reduce. (No less than 1.6mm)

 

2. Input Test

A. Test the power, the rotational speed, wind velocity, motor voltage, and motor electric current, observe whether the heat wire turns red (with no accessory, adjustable resistance or diffuser)

B. Blow the board freely at the distance of 1’’. Measure the temperature of the trip and observe whether it trips or the product is shut down within 15 minutes

 

3.Normal Temperature Test

Test method:

Run the sample at the rated power for 30 minutes. The distance between the air outlet and the thermocouple board should be 1’’. Measure the temperature of each point of the thermocouple board.

Demand:

The highest average temperature rise of the five points at the galvanic board is no more than 100 degrees.

 

4. Motor Deceleration Test No.1

Test Condition and Method:

Separate the motor of the sample and the coil holder. Connect the motor to DC supply. Connect the coil holder to the other motor with the electric cord to imitate a whole sample. Input to the motor the DC voltage which is required at the rated voltage. Input to the sample 110% of the rated power. When it reaches heat balance, the voltage of the DC motor should be reduced at the rate of 1V per minute. After the tripping of the switch, increase the motor’s voltage at the rate of 1V per minute till the tripping stops. When the hot balance is reached, record the temperature of the 52 points of the 1’’ board corresponding to the air outlet. The average temperatures of the highest 5 points are no more than 100?

Result to be recorded:

Normal voltage of motor, voltage when the tripping operation is on, voltage when the tripping operation stops, temperature record of all the points, the temperature of the highest 5 points, the average temperature of the highest 5 points, the average temperature rise of the highest 5 points.

 

5. Motor Deceleration Test No.2

Test condition and method:

Separate the motor of the sample and the coil holder. Connect the motor to DC supply. Connect the coil holder to the other motor with the electric cord to imitate a whole sample. Input to the motor the DC voltage which is required at the rated voltage. Input to the sample 110% of the rated power. When it reaches heat balance, the voltage of the DC motor should be reduced at the rate of 1V per minute. After the thermofuse is broken, short it. Under the circumstances which other conditions are the same, increase the motor’s voltage by 1V. When the hot balance is reached, record the temperature of the 52 points of the 1’’ board corresponding to the air outlet. The average temperatures of the highest 5 points are no more than 100?

Result to be recorded:

Normal voltage of motor, voltage when the thermo fuse is broken, the motor voltage at the last test, the temperature of the highest 5 points, the average temperature of the highest 5 points, the average temperature rise of the highest 5 points.

 

6. Insulation Withstand Voltage Test

Turn on the switch at the highest level. Cover the sample’s surface with metal leaf. Input the voltage of 1,000V between the metal leaf and the plug of the power cord for 1 minute.

Demand:

The leakage current should be no more than 0.5mA.

 

7. Product Coverage Test

Test condition and method:

A. Cover a piece of corkboard with two layers of thin paper. Lay the corkboard horizontal.

B. Connect the uncharged metal of the sample to the ground with a 3A fuse. Lay the sample on the corkboard. Make it work at the rated voltage or power till the hot balance is reached.

C. Cover the sample with two layers thin gauze. Make it work for 7.5 hours or run it till the final result is received.

Demand:

The 3A fuse is in good condition. There are no phenomena such as burning, smoking, charring of the white gauze or distortion of the crust.

 

8. Motor Coverage Test

Test method:

1. Fix two samples. The direction of one sample’s air outlet is parallel to horizon. The direction of the other sample’s air outlet inclines towards the angle of 45° downward.

2. Block the fan blade of the sample with some tools and cover it with two layers of gauze.

3. Switch on the product; make it run at the rated voltage for 7 hours. (Repeat the test with the switch on every single level)

Demand:

There are no phenomena such as burning, smoking, sol of the shell or the possibility that the test finger can touch the charged body. If a short circuit happens, the current at that time should be no more than 15A.

 

9. Temperature-Control Short-Circuit Abnormal Operation Test

Test condition and method:

Separate the motor of the sample and the coil holder. Connect the motor to DC supply. Connect the coil holder to the other motor with the electric cord to imitate a whole sample. Short the trip of the coil holder. Connect the motor to the DC voltage which is needed by running the product at the rated voltage. Input 110% of the rated power. When it reaches heat balance, the voltage of the DC motor should be reduced at the rate of 1V per minute till the fuse is broken.

Demand:

1. The shell should not be punched and cannot be inserted by the test finger.

2. The product should not burn or smoke;

3. Do the high voltage test by covering the sample with tin foil, 1000V, 0.5MA, 1MIN.

 

10. Air Inlet Coverage Test No.1

Test method:

Connect the uncharged exposed metal components to the ground with a fuse of 3A. Adjust the sample to the worst position according to the temperature. The product is laid in different states. Turn on the switch on the high level at 110% of the rated power. After 3 minute’s preheating, cover the air inlet with a piece of single layer gauze every 3 minutes gradually till the tripping switch works. The sample works for 7.5 hours.

Demand:

The fuse of sample and ground is normal. The cover should not melt, smoke or burn.

Result to be recorded:

The time when the fuse is broken; the number of layers of the thicker gauze.

 

11. Air Inlet Coverage Test No.2

Test method:

Connect the uncharged exposed metal components to the ground with a fuse of 3A. Adjust the sample to the worst position according to the temperature. The product is laid in different states. Turn on the switch on the high level at 110% of the rated power. After 3 minutes’ preheating, cover the air inlet with a piece of single layer gauze every 3 minutes gradually till the fuse is broken.

Demand:

3A Fuse is normal. The cover should not melt. The product should not smoke or burn.

Result to be recorded:

Time of fuse movement, number of thickened gauze layers

 

12. Air Outlet Coverage Test No.1

Test condition and method:

Connect the uncharged exposed metal components to the ground with a fuse of 3A. Adjust the sample to the worst position according to the temperature. The product is laid in different states. Turn on the switch on the high level at 110% of the rated power and make it work for 3 minutes. Block the air outlet from the top, the edge, or the bottom. The cover area is increased once every 3 minutes. The position of the cover is about 50%, 75%, 90% and 100% of the air outlet till the tripping switch works. The sample works for 7 hours.

Demand:

3A fuse to earth and fuse of sample is normal and should not burn or smoke. Cover should not melt.

(In the test report, a coverage schema is necessary.)

 

13. Air Outlet Coverage Test No.2

Test condition and method:

Test condition and method: Connect the uncharged exposed metal components to the ground with a fuse of 3A. Adjust the sample to the worst position according to the temperature. The product is laid in different states. Turn on the switch on the high level at 110% of the rated power and make it work for 3 to 5 minutes. Block the air outlet from the top, the edge or the bottom. The cover area is increased once every 3 minutes. The position of the cover is about 50%, 75%, 90% and 100% of the air outlet till the fuse is broken.

Demand:

3A fuse to earth and fuse of sample is normal and should not burn or smoke. Cover should not melt.

(In the report of test, a coverage schema is necessary.)

 

14. Drop Test

Test method:

1. Connect the uncharged exposed metal components to the ground with a fuse of 3A.

2. Switch on the sample and modulate the voltage to make it work at the rated voltage.

3. Make the sample fall on the hard board from 3 different directions at the height of 3 inches.

4. Do the insulation withstand voltage test (1000V, 1MIN, 0.5MA), input test and normal running temperature test.

Demand:

Electrified body should not be touched by the test finger. Insulation should not broke or burn in the three test. The fuse of 3A is in good condition.

 

15. Double Voltage Abnormal Operation Test

Test method:

1. Turn the transformer of the sample to the level of 120V/125V. Turn the switch on with the high level. Connect the uncharged exposed metal components to the ground with a fuse of 3A.

2. Cover the horizontal board with two layers white thin paper. Lay the sample on the board.

3. Connect the sample to the power supply of 240V/250V, 60HZ till achieving the final test result.

Demand:

The product should not burn or smoke. The cover of sample should not melt. 3A fuse is normal.

 

16. Motor Short Circuit Test

Test Method:

Short the both sides of the sample’s motor. Lay the sample on the board covered by two layers of white thin paper. Connect the uncharged exposed metal components to the ground with a fuse of 3A. Switch the product on at the rated power and make it work for 7 hours till achieving the final test result.

Demand:

The thin paper should not burn, melt or smoke. The cover of sample should not melt. 3A fuse is normal.

 

17. Component Open Circuit Test

Test method:

1. Provide an open circuit of voltage reduced heating element to the motor of the sample.

2. Lay the sample on the board covered by two layers white thin paper. Connect the uncharged exposed metal components to the ground with a fuse of 3A.

3. Switch the product on and adjust the voltage to make the product work at the rated power. Make it work for 7 hours till achieving the final test result.

Demand:

The thin paper should not burn or scorch. 3A fuse is normal and should not burn or smoke. The cover of sample should not melt.

 

18. Component Failure Test

1. Test two samples. Turn off one part of the full-wave rectification circuit of one sample. Then turn off one part of the complete rectification circuit of the other sample.

2. Connect the uncharged exposed metal components to the ground with a fuse of 3A.

3. Lay the sample on the cork board covered by two layers white thin paper. Cover the sample with two layers gauze. Switch the product on at the rated power and make it work for 7 hours till achieving the final test result.

Demand:

3A fuse is normal and should not burn or smoke. The cover should not melt. The thin paper should not scorch.

 

19. Power Cord Tensile Test

Test method:

Hang heavy objects of 35 pounds on the power cord of the sample. Pull the power cord in the most adverse direction for 1 minute.

Demand:

The internal boundary part of the power cord should not have tension because of displacement.

 

20. Power Cord Bending Test

Test method:

Fix a heave object of 1/4 pound on power cord in the position of 8 inches away from the handle of the sample. Rotate the center shaft of the handle in the horizontal direction. Move it back and force. Remove it for 540° in each direction and that is a cycle. The rate is 10 cycles per minute. The current flows through the power cord is the real work current of the sample. After 6,000 cycles, do the insulation withstand voltage test (1000V, 1MIN, 0.5MA).

Demand:

The test must be done for 6,000 cycles and the insulation withstand voltage should be successful.

 

21. Handle Bending Test

Test Method:

1. Turn on the sample at the rated voltage.

2. Bend the handle of the sample for 6,000 cycles

3. Do the insulation withstand voltage test (1000V, 1MIN, 0.5MA).

Demand:

The test must be done for 6,000 cycles. There are no insulation breaking or component damages of the sample and the insulation withstand voltage should be successful.