Help identifying alternative component Power Board

Hi, I would like to get some help in trying to obtain a Datasheet or a suggestion for an alternative part of a Power Board PCB.

Part number HM00-05015LF


Marked as component T1 in the following diagram:


By the looks of it might be a Transformer. I could not find a datasheet anywhere. I got in contact with basically all the Chinese suppliers and no one has a datasheet.

It is a current transformer. ( CT ) It measures current in the load and makes a voltage.
It looks at the current in your heater, as the current passes through J7--J6.
AT J24-18 to 19 there is a voltage of 50mV/1A. or 500mV/10A or 1.5V/30A.

Can not find an exact match. Looks like 20,000:1 transformer with a max current of 15A.

Can you still get at the small wire coming out of the plastic? (not the wire in the hole in the middle) Maybe we can repairer it. Looks like the PCB is damaged also. Maybe too late to fix it.

ronsimpson said:

It is a current transformer. ( CT ) It measures current in the load and makes a voltage.
It looks at the current in your heater, as the current passes through J7--J6.
AT J24-18 to 19 there is a voltage of 50mV/1A. or 500mV/10A or 1.5V/30A.

Can not find an exact match. Looks like 50:1 transformer with a max current of 15A.

Can you still get at the small wire coming out of the plastic? (not the wire in the hole in the middle) Maybe we can repairer it. Looks like the PCB is damaged also. Maybe too late to fix it.

Click to expand...

Thanks for the help, I am afraid the component itself is toasted and needs replacing. I don't need an exact replacement I can solder some additional legs. Thanks for the info!

If nothing else, since you say you don't need an exact replacement, you can extract a current transformer by destroying any ordinary GFCI outlet and pulling out its transformer. I've used them in projects before. Same setup as what you have, a many-turn secondary around a single wire primary.

Here's one being modified:



This one had 2 secondaries; could use just one or wire them in series as needed.

Judging by the 5A fuse consider a 5A CT 50 Hz and choose Burden R.

50mV per amp with 1K load (50uA per amp) would be 20,000 : 1 ??

Is that just a safety resistor and there is another load resistor on whatever that part connects to? It just does not look like the whole CT load circuit to me.

1000:1 is a very common ratio, and those are very cheap on such as Aliexpress.


ps. You should never put any power through a current transformer without the correct load connected, or the secondary shorted out. With an open secondary they try to emulate a tesla coil, arc across the terminals or windings and self-destruct.

rjenkinsgb said:

ps. You should never put any power through a current transformer without the correct load connected, or the secondary shorted out. With an open secondary they try to emulate a tesla coil, arc across the terminals or windings and self-destruct.

Click to expand...

Have you tested that? Probably should be in a different thread.

ronsimpson said:

Have you tested that? Probably should be in a different thread.

Click to expand...

The OP in this thread is trying to replace a faulty current transformer, apparently not understanding it is a CT rather than a conventional transformer??

Keeping the output shorted or correctly loaded to prevent dangerous conditions is the most basic rule with CTs, to avoid failure and danger.
Some example info:

rjenkinsgb said:

Keeping the output shorted or correctly loaded to prevent dangerous conditions is the most basic rule with CTs, to avoid failure and danger.

Click to expand...

Why are you assuming that they intend to run it with the output shorted or incorrectly loaded? From what I gather, they want to replace the current transformer in whatever device it came out of.

I was primarily asking (in post #6) what else connected across the CT secondary, in the overall device - so the actual CT ratio could be calculated.

The 1K resistor in the part shown seems far too high a value to be the only load, & would require a 20,000:1 ratio transformer, which is extremely unlikely. CTs normally operate in to quite low resistance loads.

It's far more likely that is purely for safety and there is eg. a 51 Ohm load on whatever that connects to; that would then give around 50mV per amp scaling, with a common 1000:1 transformer.

The warning was to avoid the OP disconnecting wires in an attempt to take readings from the transformer itself while the device is powered, which could be hazardous - the restated after Ron queried it's relevance.

(Shorting is good! Open circuit is not.)

rjenkinsgb said:

50mV per amp with 1K load (50uA per amp) would be 20,000 : 1 ??

Is that just a safety resistor and there is another load resistor on whatever that part connects to? It just does not look like the whole CT load circuit to me.

1000:1 is a very common ratio, and those are very cheap on such as Aliexpress.

https://www.aliexpress.com/item/1005003498239555.html

ps. You should never put any power through a current transformer without the correct load connected, or the secondary shorted out. With an open secondary they try to emulate a tesla coil, arc across the terminals or windings and self-destruct.

Click to expand...

The board is from a caravan fridge which is responsible to power a 220v heating element, the other 2 pins go to an MCU I will try to reverse engineer the schematics next week hopefully. Thanks for your help really appreciate it. I will try to find a 4 pin alternative.

Would you say that this would be an ok replacement?

https://www.lcsc.com/product-detail...ANGCHENG-FC-ACT25-50A-1000T-1T_C20611016.html

Regards,
Radu

The primary is just a piece of insulated wire through the centre. You only need a two-wire CT connected to the load resistor, then a power wire link through the centre to connect the power circuit.

That would be far easier to find that one that is PCB mounted with the correct pinouts.

A wire-ended CT can be stuck to the board with hot melt glue, polymer sealant or similar.

The problem is that the correct ratio is guesswork, until the total load resistance is known; though it can be recalibrated by using a different burden resistor.