galvanic isolators

Question 1

what is the purpose of a galvanic isolator?

Answer 1

to mitigate galvanic corrosion by blocking low lever galvanic current through the AC safety ground

Question 2

what is galvanic corrosion?

Answer 2

is an electrochemical process in which one metal corrodes preferentially, when in electrical contact with a different type of metal, and both metals are immersed in an electrolyte such as water.

Question 3

what are the issues with galvanic isolators? What are some solutions?

Answer 3

ISSUE: 1.Many do not meet industry standard, providing a false sense of security and leaving the boat un-protected.
2. Many do not have an adequate means of dissipating heat for fire prevention.
SOLUTION: 1.Better quality galvanic isolators with a capacitor to block the passage of galvanic current when AC leakage is present.
2.A heat sink or full carrying capacitor to prevent fires.
3. The galvanic Isolator should match or be larger than the amperage rating of the main breaker
4. They should be rated fail safe, meaning if they fail they will not jeopardize the integrity of the AC safety ground.

Question 4

what safety considerations should you take when testing a galvanic isolator?

Answer 4

1. ensure shore power cord is disconnected and exercise proper lock out tag out.
2. use extreme caution! Make sure any inverters are disconnected!
3. discharge capacitors by shorting the isolator terminals before testing and any time they become charged during testing.

Question 5

If terminals are not accessible, what else can you do to perform this test?

Answer 5

between the shorepower inlet grounding pin and the grounding bus on the AC panel being sure to discharge the capacitors by jumping these two points.

Question 6

where is the galvanic isolator usually located

Answer 6

near the shore-power inlet

Question 7

What steps do you need to take to test the diode function of the galvanic isolator?

Answer 7

1.Identify the make/model and rating/fail safe.
2.turn off the breaker on the pedestal
3.disconnect shore power cord
4.disable any inverters
5.test grounding conductor for AC voltage by probing between the shipboard AC grounding conductor and the engine negative terminal or its bus. The voltage should be near 0, if more than that DONOT PROCEED!
6. disconnect the Galvanic Isolator from grounding conductor if able.
7. short the terminals of the GI to discharge any capacitors that are present.
8.with meter in diode test mode, test between the terminals for a voltage drop around 1.4 or manufacturer spec. Allow up to 10 minutes for meter reading to stabilize as capacitor is charged.
9.record results
10.short the terminals of GI to any capacitors that are present
11.reverse the test leads and repeat step 8 and 9.
12.interperat results:
if the meter immediately settled on a number the isolator does not have a capacitor or it has failed. this should be noted and client informed that the GI is not meeting the industry standard and may not protect the vessel from corrosion.
-if the meter does not show close to the same numbers when tested in both directions or shows OL or 0, the isolator fails the test and should be replaced.

Question 8

what steps do you need to take to test the GI for presence of Galvanic current

Answer 8

1. connect to shorepower with a split cord between the cord and pedestal
2. clamp grounding conductor to measure any current present
3. if any galvanic current is present, the GI is not functioning properly
4. if more than 30 ma of current is measured, perform AC leakage testing procedures