'99 ezgo 36 volt wires overheating!!

[JohnnieB]

Originally Posted by scottyb

Can you explain this more? Currently many agree that as available voltage drops the amperage drawn for a given task increases.

True.

I guess I'll have to write a paper on this and post it here.

If you want to prove it, use a PowerStat (Variable AC transformer) to lower the voltage on a 120vac motor down to 90vac and watch the temperature rise.

[yurtle]

Originally Posted by JohnnieB

Urban Myth #2

The DC resistance doesn't change because it is determined by the length, diameter and metallurgy of the windings, but the Impedance is directly proportional to the RPM. A stalled motor has minimum impedance and maximum current while a motor spinning at quiescence have maximal impedance and minimal current as dictated by Ohm's law.

Investigate Back EMF vs. RPM vs. Amps vs. Voltage. It is all tied together and confusing as hell, but if you take it back to basic electronics, it becomes clear.

I see others have replied already, but I'll post this anyway.

At a constant voltage, as horsepower requirements go up, so does amperage, up to locked-rotor-amperage. But once voltage starts dropping, as well as the battery, does current really increase? If so, then for a given output, as voltage drops to 0 volts, amperage has to increase to infinity! Really! As your batteries die, do they lose voltage or current capacity?

[JohnnieB]

Originally Posted by yurtle

1. So are you agreeing or disagreeing with me?

2. I deal with 3 phase constant speed motors at work, and when voltage droops, so does current (and output Hp).

3. I admit, I maybe wrong with a chopper controller involved (and heavy footed driver).

1. Disagreeing.

2. Has anyone suggested to management that they run these motors at a lower voltage and save money?
I'd have to look at the circuit to explain that phenomenon.

3. Neither the type controller nor the operator's shoe size ought to change the physics involved.

[yurtle]

Originally Posted by JohnnieB

1. Disagreeing.

2. Has anyone suggested to management that they run these motors at a lower voltage and save money?
I'd have to look at the circuit to explain that phenomenon.

3. Neither the type controller nor the operator's shoe size ought to change the physics involved.

I don't care if I'm right or wrong, I just wanna figure this out.

Does the chopper controller output a constant current, based on foot position, or a constant power output, adjusting for dropping voltage? Is it really that smart? My stock Curtis series controller drops speed as voltage drops, regardless of petal position.

[yurtle]

[QUOTE=JohnnieB;653534]

2. Has anyone suggested to management that they run these motors at a lower voltage and save money?
I'd have to look at the circuit to explain that phenomenon.

I am "management". I'm not sure what you mean by "phenomenon", but we have over 500 constant speed three phase pumps/motors, and they all drop horsepower output when voltage droops. By droops, I mean the normal voltage sags that occur in the summer in the south. In one site, we receive power from three 115 kV transmission lines, but they still sag close to 10% during the hot summer.

More pumps/motors are called to make up for the reduction in output.

Again, I acknowledge that this isn't applicable for a golfcart controller that "apparently" has a constant power output.

[JohnnieB]

Originally Posted by yurtle

1. At a constant voltage, as horsepower requirements go up, so does amperage, up to locked-rotor-amperage. But once voltage starts dropping, as well as the battery, does current really increase? If so, then for a given output, as voltage drops to 0 volts, amperage has to increase to infinity! Really!

2. As your batteries die, do they lose voltage or current capacity?

1. A motor will accelerate until the applied voltage equals the the Back EMF (Actually Back EMF plus voltage drop of intrinsic resistance of the windings). If the load increases, the current will increase to maintain that RPM. If the load remains constant and the voltage decreases, the motor slows until the Back EMF once again equals the applied voltage, however the relationship between RPM and Back EMF is exponential rather than linear, so the current flow actually increase until it is limited by the current source.

2. The failure/discharge mode of a battery is an increase in internal resistance. At the molecular level, the voltage exists, but it cannot get the the terminals to be usable. This is why batteries warm up as they discharge.

Because the voltage drop across the internal resistance effectively current limits batteries, severely discharged batteries won't produce enough current to increase the current flow when the terminal voltage drops.

[lockman1]

Under my username I have....
What the ....? (insert whatever word fits your liking!)

This is the best answer to the OP's original question...

Originally Posted by scottyb

a new F&R is in order and so is some system upgrade, like fresh bigger cables & HD switch cam to help avoid a repeat of the problem.

Is it necessary to have this many "technicalities" to confuse the OP?

[JohnnieB]

Originally Posted by yurtle

................they all drop horsepower output when voltage droops.

Yep, horsepower is likely to drop when voltage drops because it is the conversion of KW-in vs. Ft/Lb-out.
The increase in current flow will be seen as increased heat being absorbed and radiated by the motor.

I guess we are saying pretty much the same thing, but differently.

[yurtle]

Originally Posted by lockman1

Under my username I have....
What the ....? (insert whatever word fits your liking!)

This is the best answer to the OP's original question...

Is it necessary to have this many "technicalities" to confuse the OP?

I didn't mean to confuse the question. I'm still confused whether a controller outputs a constant current or a constant power, given a certain petal position.

I'll admit I'm wrong by implying the current drops as voltage drops, once a controller/driver is involved. I may also be wrong in what I always was led to believe by staff. Perhaps "management" needs to leave the office and go out into the field more often!

[lockman1]

Originally Posted by yurtle

.... Perhaps "management" needs to leave the office and go out into the field more often!

Take the p*ssing match somewhere else! maybe via PM...

But, dad'lfixit needs to get his F/R switch fixed!