Author Topic: Instrument wiring  (Read 7727 times)

Hugh Conway

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Instrument wiring
« on: November 27, 2014, 09:04:29 PM »
Basic stuff for most, though I am not all that well versed in electrics.

I am wanting to add voltmeter, ammeter and frequency meter to my gen circuit.
Here's what I have:
2  150V analog meters
2  20Amp analog meters with circuit transformers
1  Vibrating reed type frequency meter (47-63Hz JBT  Model 30-FHXX)-14)

The idea is to have voltage and amp readings from each 120V leg of the 3KW  gen output, plus a frequency reading.

What I think to be correct:
Voltmeter in parallel with L1/Neutral and L2/Neutral
Ammeters taking output from CTs (with in this case, 1 turn around the CT from each L)
Frequency meter.......not too sure about this one. Can it also be wired in parallel with one of the legs? Can I use one of the CT to Ammeter outputs in parallel with the freq meter?

Can anyone provide a simple schematic so I can wire this up without damaging the instruments?

All assistance gratefully appreciated.

Cheers,
Hugh



« Last Edit: November 27, 2014, 09:07:44 PM by Hugh Conway »
JKson 6/1  (Utterpower PMG ) Off-grid
Lister 6/1 Start-O-Matic engine......running with PMG
1978 Royal Enfield (glutton for punishment by Indian iron)
1963 BMW R-27 project

dieselgman

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Re: Instrument wiring
« Reply #1 on: November 27, 2014, 09:35:12 PM »
Hugh,

Are you also using the 240vac output on your setup? What type of generator head are you dealing with? There are many viable variations in design for what you propose to instrument. Most of this is quite simple and logical.

1.) Your Frequency in Hz can be read hot-to-neutral at whatever voltage (and thus connection choice) your meter is designed for, and from any of your output windings as they will all read identical in Hz. Just match voltage range to the meter rating. It sounds like you have exactly the right idea for a 120volt meter except it should NOT be connected with the Ammeter circuits. I have seen the reed-type meters built for typical 120 volt range and also for 240 volt range - not likely both in the same meter though without some additional parts. We are talking about fairly antique meter technology here.

2.) Current readings on each hot leg would be the norm. The CT would normally actually make the turns around your power lead rather than vice versa. The CT ratio needs to match your specific meter design so that your needle movement will scale accurately. The CT is already a coil and typical design assumes a single pass of the power lead through the coil. Separate CTs and wiring for each desired current reading.

Do not connect anything additional to your CT to Ammeter circuit (this will most likely screw up your readings). Take your frequency reading direct from one of your hot legs - separate wiring.

dieselgman
« Last Edit: November 27, 2014, 09:39:45 PM by dieselgman »
ALL Things Lister/Petter - Americas
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Hugh Conway

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Re: Instrument wiring
« Reply #2 on: November 27, 2014, 09:45:59 PM »
Hugh,

Are you also using the 240vac output on your setup? What type of generator head are you dealing with? There are many viable variations in design for what you propose to instrument. Most of this is quite simple and logical.

1.) Your Frequency in Hz can be read hot-to-neutral at whatever voltage (and thus connection choice) your meter is designed for, and from any of your output windings as they will all read identical in Hz. Just match voltage range to the meter rating. It sounds like you have exactly the right idea for a 120volt meter except it should NOT be connected with the Ammeter circuits. I have seen the reed-type meters built for typical 120 volt range and also for 240 volt range - not likely both in the same meter though without some additional parts.

2.) Current readings on each hot leg would be the norm. The CT would normally actually make the turns around your power lead rather than vice versa. The CT ratio needs to match your specific meter design so that your needle movement will scale accurately. The CT is already a coil and typical design assumes a single pass of the power lead through the coil.

Do not connect anything additional to your CT to Ammeter circuit (this will most likely screw up your readings). Take your frequency reading direct from one of your hot legs - separate wiring.

dieselgman

Thanks Gary;
I am using an Utterpower PMG
I use both 240V (deep well pump and refrigeration) and 120V for all else.
Your point #2....I thought single pass as well, but diagram with the CT(which was supplied with the ammeter) shows 1 turn around the CT. I am now measuring output with a Kill-A-Watt, so can compare single pass with one turn.

"Do not connect anything additional to your CT ammeter circuit".....that makes sense.

Really is simple, just want to be sure of no smoke!

Thanks for your quick reply and confirmation.
Cheers,
Hugh
JKson 6/1  (Utterpower PMG ) Off-grid
Lister 6/1 Start-O-Matic engine......running with PMG
1978 Royal Enfield (glutton for punishment by Indian iron)
1963 BMW R-27 project

dieselgman

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Re: Instrument wiring
« Reply #3 on: November 27, 2014, 09:50:48 PM »
Hugh, what manufacturer and type of CT and meter are you using?

Hopefully some of our electrical wizards can chime in here regarding the Current Transformer design issue vis-à-vis single and multiple turns of the power lead.

dieselgman
ALL Things Lister/Petter - Americas
Lyons Kansas warehousing and rebuild operations

Hugh Conway

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Re: Instrument wiring
« Reply #4 on: November 27, 2014, 11:30:17 PM »
Ammeter and CT from eBay Asia Engineer
http://www.ebay.com/itm/370412357451?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
link shows meter and CT

Cheers, Hugh
JKson 6/1  (Utterpower PMG ) Off-grid
Lister 6/1 Start-O-Matic engine......running with PMG
1978 Royal Enfield (glutton for punishment by Indian iron)
1963 BMW R-27 project