15.00  ELECTRICAL TESTS 
     15.40   Specifications for measurements either for instruments or equipment 
     Measurement of insulation resistance
     Measurement of earth connector efficiency              Specification 500.PIS

 

MEASUREMENT OF INSULATION RESISTANCE

MEASUREMENT OF EARTH CONNECTOR EFFICIENCY
Measurement of insulation resistance (CEI EN 60335)
The Insulation measurement consists in applying of a programmed continuous voltage between the phases and the ground of the product being tested for a set time and measuring of the current which flows.
The equivalent resistance value (MW) is calculated with the formula V/I .
The test voltage is generated by a PWM (Pulse Width Modulation) circuit and it is continuously monitored for the whole duration of the test.
If the resistance value (MW = V/I) is less than the programmed value, the test is immediately suspended with a negative "Reject" result.
If the measured value is greater than the programmed value for the whole duration of the test, the test ends with a positive "Good" result.
Values which can be set for the test 
Possibility of test with 3 different voltages (250 - 500 - 1'000 Vdc).
 
  With nominal test Voltage Vdc 250
 Mohm value

 Precision % e.o.s.
 from 0.1 to 0.5

1
 from 0.5 to 5

 2 
 from 5 to 50

3
 from 50 to 500

5
 greater than 500

 not definable
 
   With nominal test Voltage Vdc 500
 Mohm value

 Precision % e.o.s.
from 0.1 to 1

1
from 1 to 10

 2 
from 10 to 100

3
from 100 to 1'000

5
greater than 1'000

 not definable
 
  With nominal test Voltage Vdc 1'000
 Mohm value

 Precision % e.o.s
from 0.2 to 2

 1
from 2 to 20

 2 
from 20 to 200

 3
from 200 to 2'000

 5
greater than 2'000

 not definable
 
   Setting and measurement resolution
Mohm value  Resolution (Mohm)
 from 0.100 to 0.999

 0.001
 from 1.00 to 9.99

 0.01 
 from 10.0 to 99.9

 0.1
 greater than 100

 1
 
Test time                            sec from 0.2 to 99.9 
 
Self-testing
If the test voltage moves out of the set tolerance, the test ends with the result "Fault" being displayed 
 
 
Measurement of earth connector efficiency (CEI EN 60335 - Art. 27.5) 
 
The measurement of the earth connector efficiency consists in applying a programmed alternating current between the ground contact present on the product being tested and any metal part of the same, for the set time and in measuring the voltage drop. The ohm value is calculated using the formula V/I.
This test is carried out with four cables (2 Voltmeter and 2 Ammeter cables) to eliminate any contact resistance. 
 
The EN 60335 legislation, art. 27.5 prescribes that this value must not exceed 0.1 W.
The applied open-circuit voltage must be 10-12 Vac. The circulating current in the closed circuit should be ³10 - ³25 A 
 
The test can be carried out in two different ways: 
Type R - By ensuring that, for the entire test time, the value of the equivalent resistance (W =V/I)
                remains between the minimum and maximum set values
                (EN 60335 legislation, art. 27.5 max. value 0.1 W.)
Type V - By making sure that the value of the voltage drop normalized with the test current
                (at 10A or 25A) lies between the minimum and maximum set values.
If the values are included in the programmed range, the test ends with a positive result.
The test ends with a negative result if the values are out of range. 
 
  Table for max. voltage drop in relation to the cable section according to CEI EN60204-1 table 7
Minimum section of cable with which the mass being tested is connected to the equipotential protection system (mm2) Maximum voltage drop allowed to the passage of a current with a value of not less than 10A (Volt)

  1.0
  1.5
  2.5
  4.0
>6.0

3.3
2.6
1.9
1.4
1.0
 
Values which can be set for the test 

 Test R
 Resistance              

 * maximum      

      W

 from

 0.001

 to

 1.000

 * minimum       

      W

 from

 0.001

 to

 1.000
   Resolution          

 0.001
   Precision    % +/-      

 2
 Nominal current      A  

 ³ 10

 or

 ³ 25
 Settling time           sec. (minimum)      

  0.50
 Test time       sec.

 from

 0.5

 to

 15
               
 Tipo V
 Voltage drop              

 * maximum      

      V ca

 from

 0.01

 to

 12.00

 * minimum       

      V ca

 from

 0.01

 to

 12.00
   Resolution     V      

 0.01
   Precision    % +/-      

 2
 Nominal current      A  

  ³ 10

 or

 ³ 25
 Settling time      sec. (minimum )      

 0.50
 Test time          sec. 

 from

 0.5

 to

 15.00

Self-testing
If the current value is less than the smallest set value, the warning "Fault" is displayed independently of the type of test (R or V).