Starter Diagram

[Kiwi_Roy]

Hi,

When I measure the starter coil to ground I get a very low reading ~ 0.3 Ohms, yikes, that's 40 Amps, but it draws ~ 6 Amps when energized.

I suspect there is a special wiring arrangement inside the starter, dual coil or contact,

If anyone has the internal drawing i would appreciate it so I can add to an upcoming troubleshooting drawing.

It's riding season, I don't feel like pulling mine off just to see how it's arranged.

Thanks

Roy

[raz]

This good general Valeo writeup links to this good electrical description. But I can't see anything about dual coil or contacts. Maybe when the starter kicks in, there's just "less power left" to the solenoid? I've never really mastered inductance anyway...

 

I also measured 0.3 ohms fwiw.

[Kiwi_Roy]

[quote name='raz' date='21 April 2010 - 08:17 AM'

I also measured 0.3 ohms fwiw.

Thanks Raz,

The article talks about a contact in the solenoid, I suspect there may be a coil in series with the armature to pull it in that gets shorted by the main contact and anothet to ground to hold the solenoid in place, I'm curious now so I will get to the bottom of it.

BTW as an apprentice one of our main tasks in the winter was refurbishing starters and generators for workmates cars, mainly old British variety. This is the first one I have seen with a planitary gear and permanent magnets, but motorbikes were all kick start back then.

[emry]

It would appear we are talking about what is known as the "stall" speed of the motor. DC motors are effectively shorted through the winding in the rotor when they are not rotating, at this time the current draw is very high but the motor is also capable of creating the largest amount of torque. As the rotor starts to rotate (current flow create a magnetic field in the rotor which causes it to move in relation to the magnets in the housing) the brushes begin to contact another winding inside the rotor. As the speed of the rotor increases the "effective" resistance also increases (more windings) this lowers the current flow, which also lower the torque until the motor reaches its "no load speed", which is when the torque it prodcues is only enough to maintain it speed.

 

For the math junkies http://lancet.mit.edu/motors/motors3.html

 

Or am I misunderstanding the question.

 

perhaps this is an better answer http://www.matronics.com/aeroelectric/articles/strtctr.pdf

[raz]

Or am I misunderstanding the question.

I think so, but I trust you are right if we talk about the starter itself. We were talking about just the solenoid. Electrically it should just be a coil, on or off.

 

Edit: Your last PDF seems to describe what we was wondering about:

 

Mystery solved I guess. Thanks!

 

This was pretty interesting reading. Especially the last page. Our OEM starter relay (Siemens V23073) is rated 20 A I think. Spec'ed inrush current capacity for the NO contact seems to be 90 A. According to John's (member here but not very active nowadays) relay study: "The GEI is rated at 25 amps for the NO contact and 20 amps for the NC, whereas the Omron is rated at 20 and 10 respectively. In my opinion, there is no basis for the higher contact ratings claimed by GEI. If anything, they should be lower than Omron's ratings when based on the same objective criteria. In further support of this, the inrush current capacity of the NO contact specified by GEI is 25 amps, as compared to 60 specified by Omron."

 

This tells me I should replace my GEI starter relay with an Omron. Or even put back the Siemens. I don't think they were bad anyway, it was the crappy sockets.

[gstallons]

You have to figure or test the amperage with the motor turning at "unloaded" r.p.m.

Electric motors have EMF and CEMF. Electromotive force and Counter electromotive force. These are calculated factors when the motor is turning at the proper r.p.m.

When the electric motor r.p.m. is not at the specified r.p.m. current (amperage) rises and you start having trouble. When the motor r.p.m. gets so low or stops turning the motor becomes a short (the low resistance you found with your meter) instead of a motor.

[gstallons]

It would appear we are talking about what is known as the "stall" speed of the motor. DC motors are effectively shorted through the winding in the rotor when they are not rotating, at this time the current draw is very high but the motor is also capable of creating the largest amount of torque. As the rotor starts to rotate (current flow create a magnetic field in the rotor which causes it to move in relation to the magnets in the housing) the brushes begin to contact another winding inside the rotor. As the speed of the rotor increases the "effective" resistance also increases (more windings) this lowers the current flow, which also lower the torque until the motor reaches its "no load speed", which is when the torque it prodcues is only enough to maintain it speed.

 

For the math junkies http://lancet.mit.ed...rs/motors3.html

 

Or am I misunderstanding the question.

 

perhaps this is an better answer http://www.matronics...les/strtctr.pdf

 

 

Good input and good articles !

[Kiwi_Roy]

I think so, but I trust you are right if we talk about the starter itself. We were talking about just the solenoid. Electrically it should just be a coil, on or off.

 

Edit: Your last PDF seems to describe what we was wondering about:

 

Mystery solved I guess. Thanks!

 

This tells me I should replace my GEI starter relay with an Omron. Or even put back the Siemens. I don't think they were bad anyway, it was the crappy sockets.

 

That's the diagram I was looking for. I suspected it was like that. When the start relay closes it energises the low resistance Red coil in series with the motor 34 amps if I'm not misstaken and the blue coil in parallel 6 Amps. The field pulls the plunger in engaging the gear in the flywheel and making the large contacts which effectivly bring the other end of the red coil to +12V. The current drops to 6 Amps (blue coil), enough to hold the solenoid in place.

Meanwhile up to 100 Amps flows through the large contacts to the motor.

 

The reason motor current drops with speed, the motor is also a generator, the faster it spins the more voltage it generates but in the opposite direction (counter EMF)

I'm not sure our motors have a series field like shown, I read it was permanent magnets.

 

You can replace the connectors in the sockets quite easily, they are available in any good auto parts store. Standard spade connectors with a barb on the back. I will post how.

 

Roy

[Kiwi_Roy]

You have to figure or test the amperage with the motor turning at "unloaded" r.p.m.

Electric motors have EMF and CEMF. Electromotive force and Counter electromotive force. These are calculated factors when the motor is turning at the proper r.p.m.

When the electric motor r.p.m. is not at the specified r.p.m. current (amperage) rises and you start having trouble. When the motor r.p.m. gets so low or stops turning the motor becomes a short (the low resistance you found with your meter) instead of a motor.

If you look at the diagram Raz posted you will se the 0.3 Ohms is due to the red coil and the armature in series, The main starter current doesn't go through the Omron relay (it would fry instantly) The red coil will draw about 34 amps for the split second it takes the solenoid to engage the gear and close the main contacts. The blue coil is much weaker ~6 amps but strong enough to hold the solenoid in place while your finger is on start so the initial load on the starter relay will be ~ 40 quickly dropping to 6

The starter according to owners manual is 1.2 kW "or 100 Amps at 12V"

I'm not sure why you say test the motor no load. Most wouldn't have a meter with a scale that high anyway. What you can do is measure the voltage drop (mV) along the starter cable and try to figure the current out from cable resistance chart.

Yes, the CEMF is due to the motor acting as a generator, the faster it spins the larger the CEMF so the current drops. Current = (EMF - CEMF) / Resistance

Roy

me, for sure

[docc]

You guys are amazing.

 

And capable, too.

 

Keep this equation in mind as well: + =

[raz]

If you look at the diagram Raz posted...

For the record I totally failed to find it. Emry did, and I just cut out a diagram from the PDF he posted.

 

Keep this equation in mind as well: + =

Yes. And lack of camshaft means much more and much less

 

 

and some :(

 

 

Last news from the camshaft guy is I will have in two weeks. One month of potential driving season will be lost then. I feel like eight years old waiting for my birthday.

[gstallons]

If you look at the diagram Raz posted you will se the 0.3 Ohms is due to the red coil and the armature in series, The main starter current doesn't go through the Omron relay (it would fry instantly) The red coil will draw about 34 amps for the split second it takes the solenoid to engage the gear and close the main contacts. The blue coil is much weaker ~6 amps but strong enough to hold the solenoid in place while your finger is on start so the initial load on the starter relay will be ~ 40 quickly dropping to 6

The starter according to owners manual is 1.2 kW "or 100 Amps at 12V"

I'm not sure why you say test the motor no load. Most wouldn't have a meter with a scale that high anyway. What you can do is measure the voltage drop (mV) along the starter cable and try to figure the current out from cable resistance chart.

Yes, the CEMF is due to the motor acting as a generator, the faster it spins the larger the CEMF so the current drops. Current = (EMF - CEMF) / Resistance

Roy

me, for sure

 

 

I suggested testing the (or any) motor unloaded to take any other factors (mechanical, wiring, etc.) out of the equation.

I saw this person replace a starter,battery,alternator and positive cable to repair a slow cranking problem. I fixed it by installing shakeproof washers on the engine block ground.

Most auto parts stores perform a no-load test on starters when selling or providing warranty on them.

You can perform a load test on a starting system if you want.

[Kiwi_Roy]

You can perform a load test on a starting system if you want.

Sorry, I wasn't being critical, I just missunderstood what you mean.

I fully agree it's very hard to do a load test on the bench.

 

Roy

[gstallons]

No hard feelings, I was just trying to help out.

I know how much mystique (and ignorance) surrounds the field and theory of electronics. I am afraid I know just enough to keep from poking metal objects into electrical outlets.