Need some electrical engineering help

I need to design a device to help "cushion" the engagement of my starter.



The starter is 28VDC (drawing up to 500 Amps) on a T58-GE-3 turbine engine
installed in a non-aircraft application. I'm told this "starter slamming" is
a 'weak link' on this engine and often causes starter failure.



I also understand there are several aftermarket 'soft start' devices
available that help reduce the 'slam' when the starter is engaged. I suspect
these devices allow the starter to use a somewhat lower voltage to engage,
begin turning, then (after a couple second delay) apply the full 28VDC. I've
'bench checked' my starter and it seems to engage fine on 12VDC.



Is this something I can do with a solenoid and a time delay? Or would I be
better off with some sort of capacitance device that applies 12VDC then
increases it to the full 28VDC?



Your comments are welcome.



Thanks!

Martin

The problem is with the 500 amps. Is this peak start current from zero
rotor speed, or an average during the start cycle.

Don't say you don't know. Measure it.

How much does it draw when you "soft start" it with a 12 volt source. What
happens if you ramp it up from 6 volts to 12 volts to 28 volts? What is the
PEAK current being drawn in the ramp-up mode?

Jim



"Martin" wrote in message
...
I need to design a device to help "cushion" the engagement of my starter.



The starter is 28VDC (drawing up to 500 Amps) on a T58-GE-3 turbine engine
installed in a non-aircraft application. I'm told this "starter slamming"
is
a 'weak link' on this engine and often causes starter failure.

"RST Engineering" wrote in message
...
The problem is with the 500 amps. Is this peak start current from zero
rotor speed, or an average during the start cycle.

Don't say you don't know. Measure it.

How much does it draw when you "soft start" it with a 12 volt source.
What
happens if you ramp it up from 6 volts to 12 volts to 28 volts? What is
the
PEAK current being drawn in the ramp-up mode?

Jim


The 500 amps is what's stamped on the label- I suspect that's the max rating
of the starter.

I'll set it up on the bench, measure the amperage at the various stages, and
bring back some more data.

Thanks,
Martin

Martin wrote:
"RST Engineering" wrote in message
...

The problem is with the 500 amps. Is this peak start current from zero
rotor speed, or an average during the start cycle.

Don't say you don't know. Measure it.

How much does it draw when you "soft start" it with a 12 volt source.

What

happens if you ramp it up from 6 volts to 12 volts to 28 volts? What is

the

PEAK current being drawn in the ramp-up mode?

Jim



The 500 amps is what's stamped on the label- I suspect that's the max rating
of the starter.

I'll set it up on the bench, measure the amperage at the various stages, and
bring back some more data.

You'll need to measure it under load...

Matt

"Matt Whiting" wrote in message
...
Martin wrote:
"RST Engineering" wrote in message
...

The problem is with the 500 amps. Is this peak start current from zero
rotor speed, or an average during the start cycle.

Don't say you don't know. Measure it.

How much does it draw when you "soft start" it with a 12 volt source.

What

happens if you ramp it up from 6 volts to 12 volts to 28 volts? What is

the

PEAK current being drawn in the ramp-up mode?

Jim



The 500 amps is what's stamped on the label- I suspect that's the max
rating
of the starter.

I'll set it up on the bench, measure the amperage at the various stages,
and
bring back some more data.

You'll need to measure it under load...

Matt


I've got some parts on order that I'll need prior to 'running it under
load', so it will be a few weeks. I'll do the series of tests and return
here with more data.

Thanks!
Martin

On Tue, 3 May 2005 17:32:05 -0700, "Martin"
wrote:

I need to design a device to help "cushion" the engagement of my starter.

GE has built many thousands of these engines and I can assure you if
there was an in-service problem they would have taken care of it. One
person thinks there is a problem and pretty soon everyone thinks there
is. It's probably nothing more than a rumor from a Viet Nam era
helicopter mechanic.

The other thing to consider is how often will you use the starter?
Most industrial users fire them up and leave them running. That's a
bunch different than the Army uses UH-1 helicopters.

Best source of accurate information is your Local GE engine rep for
that engine. Give them the part numbers and mod status and they'll
give you all the great free advise you need. I don't have the main
number with me, but Goggle and you can at least find someone that can
get your reps number and then call him.

In other words, don't try and fix a problem that probably isn't. BTW
- most turbine electric starters will momentarily peak at over 1000
amps when you hit the button. Check your car starter, it'll surprise
you.



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"Don Hammer" wrote in message
...
On Tue, 3 May 2005 17:32:05 -0700, "Martin"
wrote:

I need to design a device to help "cushion" the engagement of my starter.

GE has built many thousands of these engines and I can assure you if
there was an in-service problem they would have taken care of it. One
person thinks there is a problem and pretty soon everyone thinks there
is. It's probably nothing more than a rumor from a Viet Nam era
helicopter mechanic.

The other thing to consider is how often will you use the starter?
Most industrial users fire them up and leave them running. That's a
bunch different than the Army uses UH-1 helicopters.

Best source of accurate information is your Local GE engine rep for
that engine. Give them the part numbers and mod status and they'll
give you all the great free advise you need. I don't have the main
number with me, but Goggle and you can at least find someone that can
get your reps number and then call him.

In other words, don't try and fix a problem that probably isn't. BTW
- most turbine electric starters will momentarily peak at over 1000
amps when you hit the button. Check your car starter, it'll surprise
you.



That's good advice.

One person thinks there is a problem and pretty soon everyone thinks there
is. It's probably nothing more than a rumor from a Viet Nam era
helicopter mechanic.
So his starter likely had a problem or was not 'up to standards' and instead
of correcting the problem it was 'jury-rigged' with this "soft start" thing.

The other thing to consider is how often will you use the starter?
I'll likely be using the starter much more often than the original helo
aircrew did. Reliability is important to me, so I want to 'get this right'.

I'll get the manual for my starter and ensure it's 'up to par'. And I will
contact GE regarding that unit. They'll know more about the common failures
and should be able to guide me. That's great advice.

Thanks!
Martin

"Martin" wrote

I'll likely be using the starter much more often than the original helo
aircrew did. Reliability is important to me, so I want to 'get this
right'.

Just curious, but can you tell us what it is going to be used for?
--
Jim in NC