DickB
Well-Known Member
I have two alternators on my yacht and I would like to see if they are both generating a current. Any ideas as to how that may be done?
cheers,
cheers,
How do you test an alternator?
- Thread starter DickB
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jamesgrant
Well-Known Member
Re: How do you test an alternator? *DELETED*
Post deleted by jamesgrant
Post deleted by jamesgrant
VicS
Well-Known Member
[ QUOTE ]
I don't know why exactly, perhaps because the electricity generated has no where to go and it blows something, but I think it will knacker it.
[/ QUOTE ] Sorry that's not right. What will blow the diodes is disconnecting a running alternator from the battery (or load) . It is the voltage surge that is created when the current that is being generated suddenly has no where to go that causes the problem.
I don't know why exactly, perhaps because the electricity generated has no where to go and it blows something, but I think it will knacker it.
[/ QUOTE ] Sorry that's not right. What will blow the diodes is disconnecting a running alternator from the battery (or load) . It is the voltage surge that is created when the current that is being generated suddenly has no where to go that causes the problem.
halcyon
Well-Known Member
Are they both connected to the same battery ?
If not measure each bank.
If they are connected to the same bank, disconnect all wires from one and run engine check if you are charging the battery, repeat for the other alternator.
A dynamo will hold a residual magnetic field , and charge if you spin it. A alternator uses a rotor that retains no magnetic field, so requires the feed from the ignition warning light to generate a magnetic field and start it charging. So the disconnected one will just spin.
Brian
If not measure each bank.
If they are connected to the same bank, disconnect all wires from one and run engine check if you are charging the battery, repeat for the other alternator.
A dynamo will hold a residual magnetic field , and charge if you spin it. A alternator uses a rotor that retains no magnetic field, so requires the feed from the ignition warning light to generate a magnetic field and start it charging. So the disconnected one will just spin.
Brian
ms1
Well-Known Member
use a multimeter across your alternator output connections at fast tickover and see if it is reading 14.6 volts or thereabouts.
jamesgrant
Well-Known Member
Re: How do you test an alternator? *DELETED*
Post deleted by jamesgrant
Post deleted by jamesgrant
richardabeattie
Well-Known Member
Martin has cheated by reading and then answering the question in plain English
VicS
Well-Known Member
[ QUOTE ]
I have two alternators on my yacht and I would like to see if they are both generating a current. Any ideas as to how that may be done
[/ QUOTE ] Provided they are not connected together the simplest thing to do first is to check the voltage output from each. Use a DC voltmeter on the 20 volt range (not 12volt as was suggested elsewhere) You should get a reading that rises to something between 13.8V and 14.2V (Maybe 14.4) depending on specification as the battery charges (engine at working revs of course, not idling)
To check the current in amps is more difficult as you will have to break into the output wire and connect an ammeter in series. It will have to be able to read in excess of the rated output of the alternators which is several tens of amps. Normal multi-meters do not go that high! BUT it can be done with a meter that clips on to the wire, over the insulation with no actual electrical contact necessary, if you can borrow one.
You may find it is worthwhile taking a look at http://www.tb-training.co.uk/
I have two alternators on my yacht and I would like to see if they are both generating a current. Any ideas as to how that may be done
[/ QUOTE ] Provided they are not connected together the simplest thing to do first is to check the voltage output from each. Use a DC voltmeter on the 20 volt range (not 12volt as was suggested elsewhere) You should get a reading that rises to something between 13.8V and 14.2V (Maybe 14.4) depending on specification as the battery charges (engine at working revs of course, not idling)
To check the current in amps is more difficult as you will have to break into the output wire and connect an ammeter in series. It will have to be able to read in excess of the rated output of the alternators which is several tens of amps. Normal multi-meters do not go that high! BUT it can be done with a meter that clips on to the wire, over the insulation with no actual electrical contact necessary, if you can borrow one.
You may find it is worthwhile taking a look at http://www.tb-training.co.uk/
VicS
Well-Known Member
[ QUOTE ]
Are you saying also, that you can test a disconnected alternator by spinning it then and all will be ok?
[/ QUOTE ] No that was not what i was saying. It wont tell you anything useful if there is no load on it.
Halcyon's advice on these matters is always sound
Are you saying also, that you can test a disconnected alternator by spinning it then and all will be ok?
[/ QUOTE ] No that was not what i was saying. It wont tell you anything useful if there is no load on it.
Halcyon's advice on these matters is always sound
halcyon
Well-Known Member
Perhaps I should have stated the obvious, you test the one with wires attached.
As long as all wires are off the alternator, you will be ok spinning it while checking the other unit.
You can get a clamp ammetre / multimeter for around £10 these days ( Maplin? ), have one I throw in the tool box to give a quick answer. Howard Butler used to make a clip on meter, that just clipped on the side of the cable. They were dirt cheap, used to buy a box and give to customers to check for faults. It gave you reliable answers over the phone if there was a fault, and saved m a trip most times.
Brian
As long as all wires are off the alternator, you will be ok spinning it while checking the other unit.
You can get a clamp ammetre / multimeter for around £10 these days ( Maplin? ), have one I throw in the tool box to give a quick answer. Howard Butler used to make a clip on meter, that just clipped on the side of the cable. They were dirt cheap, used to buy a box and give to customers to check for faults. It gave you reliable answers over the phone if there was a fault, and saved m a trip most times.
Brian
VicS
Well-Known Member
[ QUOTE ]
You can get a clamp ammetre / multimeter for around £10 these days ( Maplin? ), have one
[/ QUOTE ] Not from Maplin as far as I can see. A choice of only three clamp multimeters (starting at £7.99) but none doing DC amps.
You can get a clamp ammetre / multimeter for around £10 these days ( Maplin? ), have one
[/ QUOTE ] Not from Maplin as far as I can see. A choice of only three clamp multimeters (starting at £7.99) but none doing DC amps.
Gin
Well-Known Member
[ QUOTE ]
BUT it can be done with a meter that clips on to the wire, over the insulation with no actual electrical contact necessary, if you can borrow one.
[/ QUOTE ]
I got a Sealey induction ammeter from my local motor factor for £17. It reads 75amps max but other ranges were available
BUT it can be done with a meter that clips on to the wire, over the insulation with no actual electrical contact necessary, if you can borrow one.
[/ QUOTE ]
I got a Sealey induction ammeter from my local motor factor for £17. It reads 75amps max but other ranges were available
halcyon
Well-Known Member
There is one that floats round the special offers, comes in Maplin or CPC fliers.
I'll keep a eye open if they pop up again.
Brian
I'll keep a eye open if they pop up again.
Brian
savageseadog
Well-Known Member
[ QUOTE ]
[ QUOTE ]
You can get a clamp ammetre / multimeter for around £10 these days ( Maplin? ), have one
[/ QUOTE ] Not from Maplin as far as I can see. A choice of only three clamp multimeters (starting at £7.99) but none doing DC amps.
[/ QUOTE ]An AC clamp meter would still give some indication as the output is rectified AC.
[ QUOTE ]
You can get a clamp ammetre / multimeter for around £10 these days ( Maplin? ), have one
[/ QUOTE ] Not from Maplin as far as I can see. A choice of only three clamp multimeters (starting at £7.99) but none doing DC amps.
[/ QUOTE ]An AC clamp meter would still give some indication as the output is rectified AC.
VicS
Well-Known Member
[ QUOTE ]
An AC clamp meter would still give some indication as the output is rectified AC.
[/ QUOTE ] The output is full-wave rectified 3phase AC so is going to be a lot steadier than half or even full-wave rectified single phase.
You might get a small "indication" but the reading will be totally meaningless
An AC clamp meter would still give some indication as the output is rectified AC.
[/ QUOTE ] The output is full-wave rectified 3phase AC so is going to be a lot steadier than half or even full-wave rectified single phase.
You might get a small "indication" but the reading will be totally meaningless
DickB
Well-Known Member
Thanks everyone, I will first check to see if there is a voltage from both of them. I am not sure how I will do the amperage but first things first...
cheers,
cheers,
