How to correctly use a micro ohmmeter to measure the resistance of a high-voltage motor

How to correctly use a micro ohmmeter to measure the resistance of a high-voltage motor

High voltage motor resistance measurement requires the use of specialized instruments and strict adherence to safety regulations. The specific operation is as follows:

1、 Instrument selection and wiring
instrumentation
High voltage motor resistance measurement requires the use of a micro ohmmeter (such as models that support high current output), with an accuracy of less than ± 0.1%, and can withstand high voltage environments.
Four wire system wiring
Two current wires are used to clamp the root of the lead wire, and two voltage wires are connected in parallel on the inside of the current wires to avoid contact resistance interference.
Avoid using a double arm bridge as it has weak anti-interference ability and cannot effectively eliminate the lead resistance of high-voltage motors.

2、 Test current and temperature rise control
current selection
Choose the low current mode of 0.1A~5A to avoid the impact of Joule heating on winding temperature rise and accuracy.
Large motors need to match the current according to the resistance value to ensure that the temperature rise is within an acceptable range.
environmental control
The test should be conducted at standard temperature (20 ℃) and the ambient temperature fluctuations should be strictly controlled (such as ± 2 ℃).
After testing, the discharge time should be extended to prevent residual charges from damaging the instrument.

3、 Security measures
Insulation protection
Wear high-voltage insulated gloves, insulated boots, and use insulated pads to ensure the safety of operators.
Before testing, it is necessary to confirm that the motor is completely powered off and gradually discharge using a dedicated discharge rod.
Operating Specifications
According to the requirements of the Safety Regulations, a safety distance of at least 0.7m must be maintained for high-voltage motor testing.
Avoid testing live circuits to prevent electric shock accidents.

4、 Data Processing and Standard Requirements
data recording
Calibrate the instrument before measurement to ensure accuracy.
Record the three-phase resistance values and unbalance rate (high-voltage motors require ≤ 2%), and compare them with the design values.

Common problem handling
If the resistance value is abnormal, it is necessary to check the insulation or contact points of the leads to avoid virtual high caused by the oxide layer.
The insulation damage of the Leeds line needs to be carefully inspected to ensure that the testing current penetrates the insulation layer.

By following the above steps, it is possible to accurately and safely measure the resistance of high-voltage motors.