# Rectifier/regulator

Up to ElectricalI am about to fit an Alton starter to my '72 Commando. At the moment it is fitted with a 3-phase SRM 180 watt alternator. This will be replaced by the Alton 2-phase, (single phase?) 150 watt unit.

I fitted an RGM modern rectifier/regulator a year ago, obviously for a 3-phase system. Can this be used? I read on a different blog that one just connects the two output wires of a single phase system to any two of the three spade connectors and all would be well.

Question: is that true?

Any advice welcome.

Andy Bone

Yes. It will work, but like for like power inputs in terms of rated output (watts) will stress the diodes slightly more, fortunately your new alternator has a lower output....Put simply eg: 180 watts (3 phase) rectified by 3 sets of diodes gives an average of 60 watts each whereas 180 watts (if single phase unit) divided by 2 sets give 90 watts each...but at 150 watts (your new alternator) it equals 75 watts per diode pair... but still 25% more...it will probably be OK however though but invalidate the guarantee.....which probably has expired anyway?

Les

Previously andy_bone wrote:

I am about to fit an Alton starter to my '72 Commando. At the moment it is fitted with a 3-phase SRM 180 watt alternator. This will be replaced by the Alton 2-phase, (single phase?) 150 watt unit.

I fitted an RGM modern rectifier/regulator a year ago, obviously for a 3-phase system. Can this be used? I read on a different blog that one just connects the two output wires of a single phase system to any two of the three spade connectors and all would be well.

Question: is that true?

Any advice welcome.

Andy Bone

Buy a new single phase rectifier/regulator Andover Norton do a 200 watt one. Keep the 3-phase set together. It may be expensive but how much is an Alton starter set up? That way you will not be wondering if the old one will last or weather it will be too much load one the diodes. If you are concerned by the cost you can always sell the 3 phase set up. If you knacker the old rectifier/ regulator it is worth nil. That way it is one less chance of letting you down. It is always better to have spare capacity rather than run on the limit.

Previously les_howard wrote:

Yes. It will work, but like for like power inputs in terms of rated output (watts) will stress the diodes slightly more, fortunately your new alternator has a lower output....Put simply eg: 180 watts rectified by 3 sets of diodes gives an average of 60 watts each whereas 180 watts divided by 2 sets give 90 watts each...but 150 watts (your new alternator) equals 75 watts per diode pair...25% more....will probably be OK though but invalidate the guarantee.....which probably has expired anyway?

Les

Thanks Les, that is what the blog suggested. I still have the original rectifier and zenor diode so I have backup. I just like the performance of the modern unit. The ammeter needle hardly flickers whatever the revs.

For a few quid one can source a single phase unit. I might in due course sell the SRM alternator with the rotor on ebay, with the rectifier as part of the kit.

Cheers,

Andy