Your local contact:Polarization Index Testing Devices
A PI testing device (Polarization Index Tester) is a specialized insulation measuring device used to reliably assess the condition of electrical insulation – particularly in Motors, generators, transformers, and other high voltage systems.
The device operates according to the Polarization Index method, where the insulation capability is measured and analyzed over a defined period. The insulation resistance is recorded at several time points, typically after one and ten minutes, and the PI value is calculated from the ratio of these values.
To assess the condition over longer periods, the measurement can be performed at regular intervals, for example, quarterly, semi-annually, or annually. If the PI value decreases over time, it is recommended to shorten the test intervals to react promptly to potential insulation damage.
The PI value is a reliable indicator for:
- Moisture in the insulation
- Contamination or aging
- Surface conductivity
Key Facts:
- Meaningful assessment of insulation quality
- Temperature-independent assessment
- Early detection of moisture, contamination, or aging
- Ideal for preventive maintenance and condition monitoring
- Automated measurement sequences with built-in PI calculation
MotorAnalyzer1
The entry-level model for your Motor service
CHECK YOUR MOTOR'S HEALTH!
For electric motor service and repair
For electric motor repair
For maintenance, servicing, and service
• Asynchronous, synchronous, and DC machines, brakes, transformers, coils …
• Troubleshooting and fault location
• PI and DAR Test – Testing the Motor condition
• And much more …
• Lightweight and portable
• Mains-independent operation
• PC software for printing and save
MotorAnalyzer3
The mobile ALL-IN-ONE professional model for your Motor service
CHECK YOUR MOTOR'S HEALTH!
For electric motor service and repair
For electric motor repair
For maintenance, servicing, and service
Essential test methods
- Surge test – 3 kV
- Resistance test
- Insulation resistance Test – 6 kV
- High voltage test DC – 6 kV
- Polarization Index, DAR – 6 kV
- inductance
- impedance
- Capacitance
- Turn-to-turn fault localization with probe
- Adjustment Neutral Zone
- Sense of rotation and sense of rotation
- …
- Mains-independent operation
- PC software for printing and saving
- Communication with
«» PC via Bluetooth
MTC2 R7
Universal winding test devices from 6 to 50 kV
For production, EOL, automation
For test laboratory, R&D, approval, certification tests
For repair, maintenance, and service
- Determine sense of rotation using a measuring probe in the stator
- Determine rotating field by manual rotation of the Motor shaft
surge test
- Ultra-fast 50 measurements per second
- Phase comparison between phases
- Patented peak-to-peak measurement
Partial discharge during surge test compliant with DIN EN 60034-18:2014
- Passive or active antenna
- Conducted coupling
ohmic resistance
- Winding
- Temperature sensor
insulation resistance
- IR
- PI, DAR
High voltage AC optional
Test connections
- Standard: 4
- Optional: 7 and more
Good to know:
The Polarization Index Test
A PI test device is used for the precise evaluation of the insulation quality of electrical machines – such as Motors, generators, or transformers. It measures the so-called Polarization Index (PI), a characteristic value that allows conclusions about the condition of the insulation.
Operating Principle
- Measurement Principle
The test device generates a constant DC voltage (typically 500 V to 5 kV) and measures the insulation resistances after 1 minute (R₁) and 10 minutes (R₁₀)
- Calculation
- The PI value is derived from the ratio R₁₀ / R₁.
Interpretation of Values
|
PI Value |
Insulation Assessment* |
|
< 1,0 |
Critical – severe impairment |
|
1.0–2.0 |
Borderline – further analysis recommended – action is required |
|
2.0–4.0 |
Good – insulation in satisfactory condition |
|
> 4,0 |
Very good – dry, clean insulation |
* These are guideline values without guarantee. Further specifications can be found in the relevant standards (e.g., IEEE 95-1977).
Long-term Monitoring with PI Testing
For the condition assessment of electrical insulations over longer periods, regular PI measurement is recommended – for example, annually, semi-annually, or quarterly.
If the PI value decreases over time, the test interval should be shortened to be able to react promptly to potential insulation damage.
If the PI value reaches a critical space, a preventive maintenance measure may be advisable.
This way, unplanned failures can be avoided, and maintenance or repair work can be strategically scheduled into predictable time slots – for example, during company holidays or production-free periods.
Typical Application Spaces
- Maintenance and Servicing of Electrical Machines
- Condition diagnosis before Commissioning
- Quality assurance in manufacturing
Advantages
- More conclusive than individual measurements of insulation resistance
- Automated measurement sequences with built-in PI calculation
- Documentation and evaluation possible via interfaces
The SCHLEICH product portfolio – Expect more!
Insulation, PI, and DAR test devices
- TEST VOLTAGE from 30 V up to 50,000 V DC
- Standard-compliant time-based TEST VOLTAGE profiles
- Often in combination with further test methods such as high voltage DC/AC, step voltage measurement, surge test, partial discharge measurement etc.
- Standardized interfaces such as RS 232, Ethernet / LAN, USB for PC communication
- 24 V digital I/O for PLC communication
- Expandable to Industrial Ethernet and fieldbus systems for PLC communication
- Virtually unlimited storage space for test plans and test results
- All parameters determined via the software
Custom test devices and systems
- Single and combination test devices
- Automatic test systems/test systems with relay matrix
(2, 3, 4, 6, 9, 12, 15, 18, 21 … 100 terminals) - Complete test workstations
- Production lines with transfer systems
- EOL workstations
- Large-scale systems
Comprehensive service
- Professional consultation with technical expertise
- Thorough initial Commissioning
- Regular certified calibration
- After-sales support by our service team
- Service by phone, via remote maintenance, or on-site
- Tailored training courses
- SCHLEICH.CARE.PREMIUM
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