MICROTEST MT-6920 motor rotor testing system provides 24 or 48 channels for testing. It allows for the measurement of welding resistance in motor rotors and integrates safety withstand voltage insulation and inter-coil short circuit testing in a single system. It supports PC connectivity software for remote programming and storage of test data. The system can be PLC-controlled and can accommodate customized testing fixtures for customer-provided rotors.
SPEC
| Model | MT-6920 |
| Test Channel | 24/48 |
| DC Resistance Test | |
| DCR Range | 0.1mΩ-100kΩ |
| Measuring Mode | 4-Wire |
| DCR Accuracy |
Low Resistance 0.1mΩ-1Ω±(0.2%±1mΩ) High Resistance 1Ω-100KΩ±0.1% |
| Safety Hi pot Test | |
| AC Output Voltage | 100V-3000V |
| AC Leakage Current | 0.001mA-10mA |
| AC Arcing Detection | Detect gears from 0-9 |
| DC Output Voltage | 100V-3000V |
| DC Leakage Current | 0.001mA-5mA |
| DC Arcing Detection | Detect gears from 0-9 |
| IR Output Voltage | 100V-1000V |
| Insulation Resistance | 1-9999MΩ |
| Measuring Time | 0.1-99.9s Continuously adjustable |
| Voltage Accuracy | ±(3% of setting+5V) |
| Impulse Winding Test | |
| Impulse Voltage (programmable) | 200V-3000V |
| Impulse Voltage Accuracy | ±2% |
| Total area comparison |
When layer short happened, the loss of power on coil increase, the resonance damping coefficient increase, resonance amplitude decrease, the total area decrease. These are the basic parameters we check layer short. By calculating and comparing the deference of area between golden sample and DUT. |
| Differential area comparison |
Add up the difference between normal wave and DUT wave call “ Area differential”. By calculating and comparing the deference of area between golden sample and DUT. To determine the degree of waveform overlap. |
| Wave comparison | Set a acceptable wave range, if the DUT’s wave is in this range shows “pass” otherwise, “fail” This parameter can judge both amplitude and phase of resonance wave. This can increase the detection capability of layer short. |
| Corona comparison | In pulse test, the insulation defect will cause discharge and create corona. This function is able to count the times that corona happened base on the degree of deviation. Detect the discharge phenomenon on the coil. |
| Flat comparison | If the layer short happened, the waveform will tremble. Therefore, the instrument will quantize and compared it. |
| Inductance Measurement (Option LCR Meter 6365) | |
| Inductance Ranges | 0.1nH - 99.999KH |
| Test Frequency | 10Hz-200kHz |
| Frequency Output Accuracy | ±0.01% |
| Frequency Resolution | 5 Digits |
| AC Drive Level | 10mV to 2Vrms (1m Vrms resolution) |
| Basic Accuracy | ±0.1% |
| Three-phase Inductance Balance Test |
Comparison Mode
|
SYSTEM
| Test fixture | According to the test requirements | |
| Indicator | Pass/Fail Screen Diaplay/Sound | |
| Built-in Storage | Storage of 100 rewritable data sets | |
| Operation | Manual, RS-232 | |
| Power Supply | Voltage | 90-132Vac or 198-264Vac |
| Frequency | 50/60Hz | |
| Power consumption | 300VA | |
| Environment | Temperature | 10℃-40℃ |
| Humidity | 20-90%RH | |
| Display | 6920 | 5.7" dot-matrix display (320*240) |
| 7605 | 4.3" TFT LCD (480*272) | |
|
Dimension (W*H*D) |
6920 | 435x190x522mm |
| 7605 | 435x145x522mm | |
| 6908 | 435x145x522mm | |
| Weight | 6920 | 15 Kg |
| 7605 | 14 Kg | |
| 6908 | 7 Kg | |
| Interface | RS-232 | |
Rotor Coil and Rotor Core
Rotor core is made by 0.5mm silicon steel. Medium and small AC motor’s rotor core are mostly apply on shaft. Huge motor usually apply on steady than stick on the shaft.
Rotor coil is to conduct current and create inductance. There are two type of winding, squirrel-cage and wound.
Squirrel-cage rotor is self-closing winding. There is a conduct bar in each steady and connect both side.
Wound winding rotor is insert insulate wire into core as three phase winding set and connect on slip ring. And lead the current by brush.
Quality Issue on Enameled Process
Process of Winding
Uneven DCR happen in 3-pase motor, this will cause uneven rotate.
MICROTEST 4-Wire DC Resistance measurement will be more accurate than others.
Customized test fixture for rotor coil
For Enameled Winding of Motor
MICROTEST Motor Rotor Testing System is One-Step-Test Function
Low Voltage Electrical Test + Hipot Test + Layer Short + Resistance Welding Test
Important Parameter for Quality of Coil
Inspect leakage current and Hipot by using Hipot tester. Connect one end to coil winding, and the other to silicon steel. Compare the leakage current and insulation resistance under AC and DC voltage.
The enameled wire on motor include some tiny parasitic capacitance, this feature will create leakage current because of resistance. Under AC source, capacitance is a impedance item. This may make the test result include the leakage current from the hipot tester. If the DUT has low AC leakage current, it must concern capacitance , frequency, and the voltage we use.
The inside of insulation material will discharge under high voltage test, because of the poor insulation. In this case, temporary or inconsistence discharge on DUT will happen.
Arc detection is a kind of geometric, non-constant test. The result will affected by the impedance or capacitance and current by time.
Introduction of Impulse Tester
Impulse Winding Tester use the comparison of pulse to measure the DUT. The instrument provide high voltage to do the instant pulse test and record the wave. Compare with the golden sample to define the product.
Why do we need impulse tester for producing motor/transformer?
Impulse Test = Quality and product life test
The small defection is hard to find at low voltage test station. As the DUT goes to the final assembly test, the defect may show up. This will higher the cost of production.
Motor and transformer usually work under high voltage. If we add impulse test in the product line, this may prevent the malfunction or burn on motor.
| L | is the DUT coil |
| C1, C2 | are the resonant capacitors in the instrument |
| R1, R2, R3 | is the resistant in the instrument and the DUT |
| Technology of Detect Layer Short | |
| → 1 | Charge the C1 capacitor to the certain testing voltage level. |
| → 2 | Trigger the SCR by pulse |
| → 3 | DUT will resonate with C1 and C2 |
Technology of Detect Layer Shor
“Pulse voltage and waveform comparison” is the way we detect layer short. The pulse voltage is non-destructive/instant voltage that apply on both side of winding and detect the DUT without damage it. By compare the wave with the golden sample, we can judge the DUT.
Damping wave under L/C resonate comes from the feature change of defect coil.
By comparing the wave of damping attenuation between golden sample and DUT
Provides 5 waveform comparison
Standard Accessories
| Power Cord | |
| HV Test Cable | |
| Banana Plug Cable | |
| RCA adapter (Temperature Test Prob) |  |
| RS-232 Cable | |
| D-Sub footswitch (F760001) | |
Optional Accessories
| PC Link Software | |
| Customized cabinet | |
| Test Fixture |  |
