Earth fault - motorised treadmill (long) ...

DIL-to-be? (son's current squeeze) presented a "yumcha" motorised treadmill for me to check/repair. Badged Vibelife V815. History is that it was ordered on the web, and was faulty out of the box. Supplier sent a replacement motor which was installed by a local sparky as a warranty repair, but that also didn't go. Sparky apparently then muttered "(expletive) house wiring" and left - either his payment or expertise had run out. Attempts to chase up the supplier failed as they had folded their tent and disappeared. (Warranty has expired before owner qualified as a potential DIL.)

As soon as power to the machine was enabled, it tripped the earth leakage (30mA). Opened up the machine and found no signs of damage or escaped smoke, etc. It has two motors, one for platform incline and one for belt drive. Both have explicit earth leads bolted to the frame, as is the incoming earth lead. Transformer provides low voltage for electronics board in the base frame, which also houses the control relays and diode bridge for the motors (DC drive). Console contains all display and UI controls. All good in terms of configuration.

Test 1: With power leads for both motors disconnected, the fault is still present. That's not a surprise, as I'm sure the earth leads are directly connected to the motor frames, which are directly connected to the machine frame.

Test 2: After checking other considerations, I lifted the incoming earth lead - leaving both the motor leads connected to frame and all other connections as original, and the machine operates OK.

Test 3: With transformer secondaries isolated from electronics module

- no fault. For a moment I figured this eliminates a frame-fault in the transformer, pointing to the electronic module having earth fault, BUT of course it doesn't. Either leg of either secondary could have a path to frame. Nevertheless, the resence of the eltronics module is required to complete the path to earth, so where is it?

Electronics is a pcb mounted via insulated standoffs to a large earthed heatsink. Three components use the heatsink - a 3-terminal ?volt-reg (bigger than TO-220), a TO-220-sized diode (both these use insulating washers), and the diode bridge. Apart from these, only outgoing cables:

. power to belt motor. . power to jack screw motor (incline adjust). . UI connection to all-plastic unearthed console. . speed sensor on frame adjacent belt roller.

offer the potential for that path. Motor cables had already been disconnected (test 1). Speed sensor isolation made no difference. Without UI connected, nothing at all happens. So the focus is back on those three heat-sunk devices next time I look at it.

Yes, I DO know what I am doing around mains power, thanks for your concern, or I wouldn't be working on an unearthed machine with a demonstrated earth leakage issue even with upstream ELCB/RCD protection.

Any comments on the fault-finding process so far? Anyone had to work on one of these?

Reply to
who where
Loading thread data ...

"who where"

( snip piles of drivel )

** Have you checked to see if safety earth and neutral are connected ?

I mean a simple ohm meter test on the AC plug.

Also check if any suppression caps go from active to ground.

Always start with the basics.

... Phil

Reply to
Phil Allison

8< - - --------------------

That thing is rated at 6.5 hp. What have you got it plugged into?

Reply to
Metro

Heh, that was one of my first observations since it comes with a 10A plug-top. The belt motor is labelled 220V (DC) at 11.4A, but on tong-test the whole machine shows a tad over 1A AC input at 12kph with a victim up a 10% slope, so I suspect that's an out-of-someone's-arse number to make the sales pitch more impressive. Clearly the "Leeson USA" motor is still loafing if the input is ~ 300W.

All fixed now. Silpad under the motor drive IGBT had a perfectly circular ~0.8mm dia hole so instead of providing ~ 4kV isolation the motor drive on the IGBT tab was arcing straight through the hole (about 4cm from the "QC" sticker on the heatsink). Cleanup, new silpad and compound and it's running better than new ....

Reply to
who where

"who where"

** Nice one - that is a " result " .

... Phil

Reply to
Phil Allison

After an "event"

Reply to
Metro

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.