Help with DC Motor from Treadmill

[combatwombat_nz]

Hi guys... I'm first timer with this stuff, and new to this forum, but have enough electronics knowledge to be dangerous (used to fix slide projectors and such, now fix computers for a living)... anyhow, down to the question:

Wifey bought a treadmill secondhand. No manual. No data sheets. No go. My job is to fix it.

It is a Sportrack Treadmill, apparently out of China. I am in NZ on 240V, and this is a 240V device. Upon turning on, it shows a Dist reading of 2.5, then E2 in the error register, and "KM" in the main led screen.

It runs with a Power Conversion/Control board, that takes the AC down to DC for the User Control board, and DC for the Treadmill motor, and branches out with AC for the Incliner motor.

The problem appears to be the DC driving the Treadmill motor. The motor has the following on it's label:
Catalog A1D061. HP:2. RPM: 4000. Volts: 180. Amp: 8.5.

The output from the PCB to the motor is DC 140V constant from power on. Tested with digital multimeter.

So, is the voltage supposed to be higher, ie 180V, or will it go higher when then machine is set into motion? Or is the motor toast, as I thought it should have responded to an input of 140V? Surely the POST diagnostics of the system should do a quick check of the motor, and it's ability to respond - therefore why does the voltage stay at 140V with this error message, rather than going up there, then coming back down?

Or am I barking up the wrong tree?

TIA

 

[Diver300]

How many wires go to the motor?

I guess that there are 4, and it has a field winding and an armature.

140 V on the field winding sounds about right. It will need voltage on both the field and the armature to run. If power is put onto the armature only, the motor is likely to burn out, so it looks like there isn't any power getting to the motor.

If there are only two wires, it is likely to be a permanent magnet motor, and it would at least rotate on 140 V unless it had failed.

Can you measure the current?

 

[combatwombat_nz]

Hi, thanks for the reply. The motor has 3 wires - Red,black,green/yellow.
I checked the Amperage and Volts with motor connected. Zero.
Checked the red to black connectivity of the motor alone. Fully connected with 2.6ohm resistance. A motor should have more than that as the coil resistance, shouldn't it?

 

[jpanhalt]

Sounds like the motor may be a permanent magnet type -- two wires and a ground. When you turn the motor, does it turn freely or tend to cog? If you short the terminals of the motor, does it get harder to turn. Be sure it is not plugged in during those tests.

John

 

[combatwombat_nz]

Rolls freely whichever way.

 

[jpanhalt]

Two factors to consider: 1) motor; and 2) controller.

1) Your motor could have a wound field, but if it is permanent magnet and turns that freely, then it may be shot. Will a piece of steel (paper clip) stick to the motor case? Does the motor have brushes (I assume it does)? Maybe the brushes or connections to the brushes are bad (open circuit). I have seen the pressure spring slip off of the brushes on smaller motors. If it were mine, I would disassemble it and take a look. But first, I would consider the controller.

2) The fact that you get zero volts with the motor connected and no sparking (I assume) raises my concern that the controller may be bad. In other words, the 140 volts you see open circuit is not representative of what it should really supply. Once under load, its voltage drops to zero. If the ammeter was in-line, read zero, and your measurement across the motor terminals was zero volts, I would strongly suspect the controller. Do you have any way at all of getting another DC supply at 120 to 180 volts? Even lower voltage would tell you whether the motor responded by humming or moving slightly.

John

 

[Ubergeek63]

it is a 2HP DC motor. it is very common for these not to have noticeable cogging. you should, however notice a distinct resistance to turning when the motor is shorted.

check the brushes.

it is probably a "loss of signal" error indicating that it is not getting back a signal from the belt speed sensor.

that is a reasonable armature resistance. DVMs are not good at averaging PWM readings, get the voltage reading with say a 1K-1u RC filter. I think the error is defaulting to a minimum PWM and your meter is reading it wrong. check the speed sensor.

Dan

 

[combatwombat_nz]

Thanks John and Dan.
Dan, you've just about lost me in the TLAs ;-)
The motor is a sod to get into, but I can get through two little windows in it's housing, to unclip and leave dangling the brushes. I guess they look ok, not that I really have any experience looking at those. Nothing clings magnetically to the housing.
The "belt speed sensor" I am presuming is the small reed switch that meets the belt shaft/wheel. The switch appears to work correctly - open circuit until the magnet in the wheel line up with it, then it's closed.
"get the voltage reading with say a 1K-1u RC filter." Sorry, dude. Right over my head. Does this tell me what I need to know about doing that? :RC circuit - Wikipedia, the free encyclopedia

 

[combatwombat_nz]

On a suggestion from a friend, I hooked a normal incandescent light bulb to the power output from the controller board. It would not light up at all.

So it does appear that the circuit fails totally when it goes under load.

I guess I just need to replace components on the controller that follow back from the connectors for the motor?

Not as easy as it sounds... I can't get the PCB to budge from it's aluminium frame!

Components I can identify from markings:
1 small resistorurple band/goldband
1 small capacitor: 102K 1KV
2 large resistance wires in series, with heat shrink over them. Denoted as RT1 and RT2 on the PCB.
3 Heatsinked components:
-"D2" 3-connector with FEP30JP screenprinted, and a diagram of dual diodes headed to centre.
-"Fet1" and "Fet3" 3-connector. Screenprinting: Morocco 3927 27149 IRFP450, and Morocco K930 30474 IRFP450 {N-CHANNEL 500V - 0.31 OMH - 14A - TO-247 POWERMESH II MOSFET} - from Google
1 Small resistor - red red black gold
1 Relay RL1 ... 832A-1A-C 12v DC 30A 277 AC Song Chuan
1 Bridge rectifier... GW MB3510W


Any suspects?
TIA

 

[combatwombat_nz]

Testing using the RC circuit shows a 120V DC output from the controller BEFORE load. Under load = 0.

 

[Ubergeek63]

that would be typical of a circuit running on 120V.

The voltage dropping to 0V as soon as you load it sounds like the output IGBT is blown and the voltage is comming from the snubber capacitor.

you also said that the motor seems to be demagged. consumer goods tend to cut corners. I think you might have had an underated IGBT that shorted. the shorted IGBT would then have demagged the motor which then burned the IGBT open.

So my suspicion is that you have bad IGBT and motor, as well as a marginal design that is likely to fail the same way in the the future if you replace the parts without at least upping the IGBT and heat sink.

 

[combatwombat_nz]

Thanks for the reply, Ubergeek63.

So the IGBT is which component I've listed? Or is it the combination of the two MOSFETs and their Rectifier (fep30jp)?

Unsure of whether the motor is damaged or not- nothing to drive it with so cannot test it.

 

[vnaidu]

Hey there,

I know it’s been a long time since this post was active, but did you end up fixing your problem with this “Sportsrack” treadmill? I am having the exact same problem with my work colleagues’ treadmill I'm trying to fix.
No buttons work at all & says "E2" on the right/hand display.

I have successfully tested the motor and that’s working fine, I have also tested the MOSFET's and they are also fine.

My next task is to power up the motor controller pcb separately and provide an external 5V to the input pins one at a time e.g. the start/stop or speed up pin on the pcb and see if anything happens on the output pins. This will then tell me wether it’s the input console that’s faulty.

Any help would be great.


Thanks in advance
Vijay N

 

[Ubergeek63]

Hey there,

I know it’s been a long time since this post was active, but did you end up fixing your problem with this “Sportsrack” treadmill? I am having the exact same problem with my work colleagues’ treadmill I'm trying to fix.
No buttons work at all & says "E2" on the right/hand display.

I have successfully tested the motor and that’s working fine, I have also tested the MOSFET's and they are also fine.

My next task is to power up the motor controller pcb separately and provide an external 5V to the input pins one at a time e.g. the start/stop or speed up pin on the pcb and see if anything happens on the output pins. This will then tell me wether it’s the input console that’s faulty.

Any help would be great.


Thanks in advance
Vijay N

how descriptive of them: ERROR #2 - gotta love those lazy programmers.... ours at least try, if we only have 2 digits (grade) pot out of range becomes PO. (even "pot out of range" is a "fatal error" that completely locks down the treadmill on the assumption that the grade motor is endlessly driving into the stop)

i am not sure about crap mills, but i know our linears all use a low frequency PWM (100-1000Hz) to communicate the speed command to the motor board.

if you have a serial com link it could be reporting a power board fault and then justifiably refusing to do anything else.

there is also the safety harness, but that is not a fatal error and would not be spewing that cryptic E2 you are seeing. In fact, is sounds like the mill you are looking at the harness would just be a hard disable on the motor control.

Dan

 

[vnaidu]

Thanks Dan

Strange because it has a massive main display that has at least 100 segments that light up individually. You would think they would use that to display the error code!
Anyway no it doesn't have the serial com link, there is only two sets of cables that go between the power board and console: speed sensor cable & input cable (this cable also has the Vcc and Ground pins to the console).

I tested the input cable pins on the power board and the only pins that would respond to was the incline up and down pins.

 

[Ubergeek63]

Thanks Dan

Strange because it has a massive main display that has at least 100 segments that light up individually. You would think they would use that to display the error code!
Anyway no it doesn't have the serial com link, there is only two sets of cables that go between the power board and console: speed sensor cable & input cable (this cable also has the Vcc and Ground pins to the console).

I tested the input cable pins on the power board and the only pins that would respond to was the incline up and down pins.

one should be speed command that is probably a PWM. the up and down are just turning on the grade relays. there would need to be at least a zero for the grade or a grade pot. a motor power control that usually goes to a relay that physically cuts power to the motor for safety in case of semiconductor failure. and perhaps a power cut off for the motor control.

Dan

 

[jayarajankb]

try to check E2 may be it is a problem of speed sensor circuit.try replacing sensor. sensors
already available in the market.confirm error code then proceed.