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Soken DAC-MAT-5 - Automatic Insulation Testing Set

Automatic Insulation Testing Set


Category : Insulation Tester

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The automatic insulation testing set DAC-MAT-5 is a testing set that can automatically measure the insulation of wired coil for appliances such as low voltage generators. With this one set, measurement of insulator resistance, direct current absorption (PI), and capacitance tangent (tanδ) can be done continuously without changing wiring after each test. Therefore testing time can be greatly reduced, and this set is the best choice for on-site insulation testing. The measured data is automatically saved in internal memory and can be exported to personal computers using the attached exportation software. Thus, printing reports of measurement results can be easily done.


Test Items


Measurement Method

  • Always record temperature and humidity when measuring. Measurements are easily influenced by temperature and humidity, so the recording is necessary.
  • Compare measured value directly after stopping and measured value after a while. If there is a difference, internal absorption of humidity as well as surface dirt can be considered as a cause.
  • Compare with past data, and do not determine using only the measured value. There is a difference in data based on sample structure, size, and voltage, so comparison with last measured data is recommended.

Connection Diagram

Insulation Resistance Test

For the insulation resistance test, one minute value for one of DC250V, 500V, 1000V is measured. The resistance depends on the size, structure, and voltage of the rotating machine, so analysis should be done based on change after time, not by the size of absolute value.

[Allowed minimum limit]
R(MΩ)=Rated voltage (v)/Rated power(KW) + 1000

DC Absorption Test


DC Absorption Test

In the Direct Current Absorption Test, Polarization Index (PI) is obtained by conducting with either
DC500V or DC1000V, and measuring the current in after one minute and ten minutes. If the insulating layer is humid, or there is dirt on the surface, the leakage current will be larger, and the polarization index becomes smaller.

Polarization Index (PI) = Current after 1 minute /
Current after 10 minutes 


Tan Delta Test (tanδ)

The capacitance tangent (tanδ) test is conducted by changing the voltage between AC100V to 500V. tan δ0 is a specific value depending on the material but may change due to dirt on surface or insulator degradation. Therefore, by observing the change in tan δ0, the humidity inside the insulating layer can be implied. △tanδincreases with the start of partial discharge, but tanδmay increase with voltage increase for other reasons, so watch out for this,

tanδ 0: < 10%; △tanδ < 1

Tan Delta Test (tanδ)


Dissipation Power Factor Tan Delta Test (tanδ test)

When alternating current is applied to an insulator pinched by electrodes, if there is no loss in the insulator, the phase of the current is advanced by 90 degrees compared to the applied voltage. However, in insulators, there is dissipation by leakage current (WI), induced polarization (Wp), and partial discharge (Wi), therefore the current flowing through the insulator (Ix) is delayed by δ compared to 90 degrees. δis proportional to the loss, and this delay angle δ is called dielectric loss angle. Fig. 1 is a vector diagram of the voltage applied to the insulator and current. The current flowing through the insulator (Ix) can be separated into the charge current (I0) and dissipation current (IR). The ratio of charge current and dissipation current (IR / I0) is tan δ or the polarization tangent. tan δ is a material-specific value regardless of the shape and dimensions of the insulator and can be used to describe the property of the insulator. The ratio of current (Ix) and (IR) is cosθ or dielectric power factor, and this value is sometimes used in the evaluation of insulators.

[Appliances and equivalent circuits] 

In general, the breakdown of insulators for rotating machines and transformers are believed to be caused by the degradation of enamel coating for coil wiring and protective insulating materials. In this case, the equivalent circuit will include capacitance and will look like the one shown in Fig. 1. C and tanδwill be measured between the powered part and ground. Fig 1 shows the case for a rotating machine.

The symbols for the equivalent circuit are as follows. (Measured value is synthesized value.)

  • R1: Equivalent resistance of wiring (can be almost ignored for tan δ)
  • C1: Capacitance for enamel coating
  • tan δ1: Capacitance loss of enamel coating (specific value)
  • C2: Total capacitance of the material for improving insulation
  • tan δ2: Total specific capacitance loss of the material for improving insulation
  • R2: Total DC leakage current of the material for improving insulation (cannot be measured in meg
  • ohm resistance test)
  • RM: DC leakage current of the outside (measured value of meg ohm resistance test)
Soken DAC-MAT-5 - Automatic Insulation Testing Set
  • Measurement of Mega ohm resistance, PI, tanδ using one device
  • Small, lightweight (6kg), compact and portable
  • Measured data are stored in internal memory (can be exported to PC) 


Insulation Resistance Test

Test Range
DC250V100KΩ ~ 2.00GΩ
DC500V1MΩ ~ 9.99GΩ
DC1000V1MΩ ~ 9.99GΩ
Accuracy±(10% of rdg+1digit) <1MΩ
±(5% of rdg+1digit) 1MΩ~1GΩ
±(10% of rdg+1digit) >1GΩ


DC Absorption Test (PI)

Test voltageDC500V/1000V
Test Range1μA~9.99mA
Accuracy±(5% of rdg+1digit)
Test duration1 to 10 minutes (Settable on a minute-by minute basis


Tan Delta Test (tanδ)

Test VoltageAC100V~500V 50/60Hz
Test Range
Capacitance1nF~100nF AC100V~500V
1nF~200nF AC100V~250V
Capacitance±(2%の rdg+1digit)



Power SupplyAC100V~250V±10% 50/60Hz
Size (mm)W323 x H134 x D288
AccessoriesMeasuring Cable x 1, Power Cable x 1, Grounding Cable x 1, Rotating Light x 1, Storage Bag x 1
OptionalThermal Printer, Aluminum Hard Case

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