"Test Application of Insulation Multimeter
When debugging the AC drive system, an insulation multimeter must be used to test the insulation of the main circuit and control circuit of the inverter and the motor respectively, so as to ensure the safe operation of the system. The Fluke1587 Insulation Multimeter (Figure 1-1) not only performs fast and accurate measurements of the main circuit, but also provides a 'resistance gear' function for insulation testing of the control circuit.
1. Use the Fluke1587 insulation multimeter to measure the insulation of the main circuit of the inverter (take VACONNXP as an example) and follow the steps below:
(1) Disconnect all the wiring between the inverter and the outside world to ensure that the circuit under test is not connected to any power supply. Then short-circuit the input terminals L1, L2, L3 and the output terminals U, V, W, as shown in Figure 2-1.
(2) Insert the test probe of the Fluke insulation multimeter into the '+, input terminal, and then connect the other end of the ' to the 'ground point' as shown in Figure 2-2.
(3) Connect the probe to the circuit to be tested, and the insulation multimeter will automatically detect whether the circuit is powered on. If the voltage in the circuit exceeds 30Vacordcjlj the test is automatically disabled.
(4) Select the 'Insulationtest' test function on the Fluke1587 Insulation Multimeter.
(5) Select the appropriate test voltage (500Vdc) through the 'Range' button.
(6) Press and hold the 'Insulationtest' button to read the impedance value displayed on the insulation multimeter. It may take a few seconds for the reading to stabilize. The higher the impedance value, the better. At this time, the reading is 550 megohms, and it can be judged that the insulation is good. Figure 2-3.
(7) Continue to leave the probe of the insulation multimeter on the test point, then release the 'Insulationtest' button. The circuit under test begins to discharge through the meter until it ends.
2. When measuring the insulation of the inverter control circuit (taking VACONNXP products as an example), it should be noted that the continuity test must be carried out with the 'resistance gear' of the Fluke1587 insulation multimeter strap.
3. When using an insulation multimeter to test the motor insulation, the U, V, W three-phase winding wires should be tested respectively relative to the ground wire. The general measurement value is >=5 megohms, which means the insulation is good.
