Current transformer and Regenerative VFDs?

busarider29

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busarider29
Join Date
Aug 2013
Location
Midland, MI
Posts
398
Greetings experts,

Can current transformers be used on the incoming mains (480, 3P) of a machine that has regenerative VFD's? Current transformers care about current polarity, and the secondary current is typically 0-1A or 0-5A. What happens to the current transformer when the VFD is regenerating and current is flowing in the opposite direction? Will damage occur to the transformer and/or the controls input for which the secondary current is terminated to. This is my first experience with regenerative VFDs.

Thanks.
 
That is an interesting problem. The polarity will be reversed, so you would need a signal conditioner capable of measuring a bipolar signal. There might be a product on the market with this capability built in, but a quick search didn't yield anything. What is the expected primary current range?
 
With alternating current, measuring the intensity is not enough to know the energy that circulates or in which direction it circulates, in fact an intensity can pass but without any energy transport in case it is 100% reactive intensity.

It is necessary to install an energy meter, a bidirectional one.
 
busarider29 said:
Greetings experts,

Can current transformers be used on the incoming mains (480, 3P) of a machine that has regenerative VFD's? Current transformers care about current polarity, and the secondary current is typically 0-1A or 0-5A. What happens to the current transformer when the VFD is regenerating and current is flowing in the opposite direction? Will damage occur to the transformer and/or the controls input for which the secondary current is terminated to. This is my first experience with regenerative VFDs.

Thanks.
Click to expand...

I doubt that you'd do any damage. It's AC either way.
 
I agree with the statement upstairs, you have to check whether the data of fvd itself can provide you with valid and necessary data.
 
any good VFD should provide that data as stated above.
But even of the customer demands current transformers in the spec, a 0,1A reduction wouldn't make a noticeable difference to me.
How precise of a reading is being demanded?
 

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