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Edtwozeronine: We are using the fusing characteristics of the 3A and 5A to provide information on the average current being drawn by the treadmill over a one hour period, viz:

Current In – The maximum value of current that the fuse link will carry continuously without deterioration under specified conditions.

Conventional Time – The time specified for which the fuse shall carry non-fusing current or operate within for fusing current. Conventional times are: 1 hour for ratings of 63A and below 2 hour for ratings above 63A and up to 160A 3 hours for ratings above 160A and up to 400A 4 hours for ratings above 40A

Conventional Fusing Current If – The value of current which causes operation of the fuse link within the ‘conventional time’ (usually 1.6 x In); previously known as “minimum fusing current”. Conventional Non-fusing Current (Inf) – The value of current which the fuse will carry for the conventional time without operating (usually 1.25 x In).

So, for the 13A fuse, 1.25 x 13 = 16.25A and 1.6 x 13 = 20.8A.
For 5A - 6.25A/8A
For 3A - 3.75A/4.8A

The thermal functionality of an MCB/RCBO is designed to trip after one hour when the average current through it is 1.45 x I, so for 16A mcb, 1.45 x 16 = 23.2A

See:

www.beama.org.uk/asset/A3738A16-B693-4354-9BA38AB49204773F/

and

 
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So far just tested the treadmill with load (AKA me!) on a 3a fuse, it pinged off at the 24 minute mark at the RCBO in the garage. I'm pretty cream crackered after todays garden werk, so I'll try the 5a fuse tomorrow.

Beep tested the 3a fuse at 0.06 ohms, the saga continues!
 
I noted that the motor turns easily and all rollers, etcetera are moving freely and the belt has been lubricated.

Have you changed the brushes yet?

My hypothesis is that the motor's insulation resistance is decreasing as it warms up, most markedly when the treadmill is on load (and a significant load at that :)).

As a result, the earth leakage current of the motor is increasing with time(temperature) and of course is added to the normal earth leakage of the EMI filter. I guess the motor controller is a PWM type since motor is a PM one.

It is observed that the RCBO does not trip when the treadmill is run unloaded - thus much decreased work by the motor, less Ohmic heating heat, less temperature rise, less motor earth leakage....total earth leakage does not then cause the the RCBO to trip.

When run hot or hotter than designed, a motor's insulation resistance can be expected to reduce over time.

By the by, there may be a secondary effect of high temperature causing the demagnetisation over its lifetime of the motor's permanent magnets - the result would be that a higher armature current would be required to create the same torque...thus more Ohmic heating.....

I think you are at the stage of asking a motor specialist to test out the motor.

 
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I'm thinking you need some-one local with some "Insulation resistance kit" to investigate your black dust deposits ... "Don't inhale" - it's not good for lungs.
With keen eyesight may have some tracking happening, as currents vary ,and volts spike a bit higher.
(Strange substance found in early telephone microphones)

Marconi's what to check for images - were a good start.

-If 3A fuse survived a Tripping of power incident ,doesn't look like an overload.

Do the lights ever flicker in the building with any correlation to trip event ?
 
DPG: I acknowledge your generous comparison, but I would prefer to be likened to DCI Gene Hunt. If you watched the TV series (Life on Mars and Ashes to Ashes) his deputy was the gorgeous Keeley Hawes, it was the 70s so no PC, he drove an Audi Quattro (when they were cool) and most of all he was consummate with the ad lib one-liners, viz:

 
I noted that the motor turns easily and all rollers, etcetera are moving freely and the belt has been lubricated.

Have you changed the brushes yet?

My hypothesis is that the motor's insulation resistance is decreasing as it warms up, most markedly when the treadmill is on load (and a significant load at that :)).

As a result, the earth leakage current of the motor is increasing with time(temperature) and of course is added to the normal earth leakage of the EMI filter. I guess the motor controller is a PWM type since motor is a PM one.

It is observed that the RCBO does not trip when the treadmill is run unloaded - thus much decreased work by the motor, less Ohmic heating heat, less temperature rise, less motor earth leakage....total earth leakage does not then cause the the RCBO to trip.

When run hot or hotter than designed, a motor's insulation resistance can be expected to reduce over time.

By the by, there may be a secondary effect of high temperature causing the demagnetisation over its lifetime of the motor's permanent magnets - the result would be that a higher armature current would be required to create the same torque...thus more Ohmic heating.....

I think you are at the stage of asking a motor specialist to test out the motor.


Not yet changed the brushes governor! It's finding the right size that's the problem.17mm W by 6mm D by 14mm L the length being what it is worn down to, so no idea about the original length.

Guess I'll hacksaw off the earth pin if that's the boy giving trouble!:bomb:
 
So, for the 5A fuse at least another 4 one hour sessions. And the same for the 3A fuse. Remember to run it first for an hour 'off load' before each session of running.

Alas, I am not infallible so could be completely off the mark.

Static Zap makes some good remarks on possible causes. It would helpful if you could look at the commutator and brushes and compare them to the guide I pointed you to.

I admire your willpower to use a treadmill - I found them mind numbing.
 
I'm thinking you need some-one local with some "Insulation resistance kit" to investigate your black dust deposits ... "Don't inhale" - it's not good for lungs.
With keen eyesight may have some tracking happening, as currents vary ,and volts spike a bit higher.
(Strange substance found in early telephone microphones)

Marconi's what to check for images - were a good start.

-If 3A fuse survived a Tripping of power incident ,doesn't look like an overload.

Do the lights ever flicker in the building with any correlation to trip event ?

I think the dust was just a bit of carbon brush wear and tear, since the treadmill has it's own circuit - it's the only thing to trip these days! It used to be on the ring on a 32a rcbo, one of the reasons I wanted it to have it's own circuit. No more TVs, Computers or Sound Systems all going off without a moments notice.
 

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