Clinical Laboratory Centrifuge Electrical Safety

[Luanne]

In our shop we have a difference of opinion about WHEN to measure current leakage. I was taught that current leakage should be measured with the unit off and again on while running at max speed. I know that the maximum allowed current leakage is 500 uA but is there anything in the regulations that specify AT WHAT POINT IN THE CYCLE to measure the peak leakage?

 

[T.M.Haja Sahib]

In our shop we have a difference of opinion about WHEN to measure current leakage.

Naturally,current leakage is maximum,when the load current is maximum.So check up,when the centrifuge is taking maximum load.

 

[charlie b]

I know that the maximum allowed current leakage is 500 uA. . . .

Maximum allowed by what? The primary regulation most of us deal with is the National Electrical Code, and the maximum limit you describe is not contained therein. Is it somewhere in the manufacturer's documentation, or perhaps in a regulation more closely related to your field? If so, those are the places I would look for guidance on the method of testing. In my world, we don't want any leakage, but we don't have a specific limit. Also, we have no tools that are capable of measuring a current as small as 500 uA. So I am afraid that I cannot help you on this one. Good luck.

 

[T.M.Haja Sahib]

A noticeable shock can be felt at a leakage current of 0.5mA.This criterion may be used in the absence of a suitable meter.

Maximum allowed by what? The primary regulation most of us deal with is the National Electrical Code, and the maximum limit you describe is not contained therein. Is it somewhere in the manufacturer's documentation, or perhaps in a regulation more closely related to your field? If so, those are the places I would look for guidance on the method of testing. In my world, we don't want any leakage, but we don't have a specific limit. Also, we have no tools that are capable of measuring a current as small as 500 uA. So I am afraid that I cannot help you on this one. Good luck.

 

[don_resqcapt19]

A noticeable shock can be felt at a leakage current of 0.5mA.This criterion may be used in the absence of a suitable meter.

Not really. You have no idea what the current is so you can't use the shock method to find leakage. There are meters designed for this purpose.

 

[don_resqcapt19]

In our shop we have a difference of opinion about WHEN to measure current leakage. I was taught that current leakage should be measured with the unit off and again on while running at max speed. I know that the maximum allowed current leakage is 500 uA but is there anything in the regulations that specify AT WHAT POINT IN THE CYCLE to measure the peak leakage?

I would expect that the 0.5mA is a maximum and that it would apply under all conditions of use or non-use. You need to test both off and under all loading conditions.

 

[T.M.Haja Sahib]

Not really. You have no idea what the current is so you can't use the shock method to find leakage. There are meters designed for this purpose.

You are correct.My suggestion was purely academic and the responsibility for its safe use rests with any one who wants to make a practical use of it.

 

[T.M.Haja Sahib]

I would expect that the 0.5mA is a maximum and that it would apply under all conditions of use or non-use. You need to test both off and under all loading conditions.

Manuals on small appliances servicing limit permissible leakage current to 0.1 mA, as noticeable shock can be felt at a leakage current of 0.5 mA.

 

[don_resqcapt19]

Manuals on small appliances servicing limit permissible leakage current to 0.1 mA, as noticeable shock can be felt at a leakage current of 0.5 mA.

The UL standards for residential appliances permit leakage of up to 0.5mA.