600 rr coil mod / higher voltage? - Page 2 - Honda RC51 Forum : RC51 Motorcycle Forums
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post #11 of 28 (permalink) Old 10-01-2019, 11:00 AM
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i'd just check for ground faults on the input terminals of the coil. check the resistance vs a known good one (or manual specified resistance), and then check (with a megger set to 100v) for ground faults between the input terminals and the iron core. of course also check for ground faults in the wiring between the CDI and the coil.

it's not as simple to check impedance though i suppose you could use a source and measure current in the failed coil vs a known good one.


either way, the failure is the transistors. you have to think that the discharge current to the coil goes through the transistor (when called to fire by the ecm with a 5v gate pulse), at high rpm this can be a fairly rapidly occurring event. so anything that increases current through the circuit can damage the transistors. they're not exactly high current devices.

Last edited by Wibbly; 10-01-2019 at 11:19 AM.
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post #12 of 28 (permalink) Old 10-01-2019, 07:23 PM
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Your "leak" would go straight to ground. The coil itself is bolted to the grounded subframe, and has a large ferrous core. Any issues there aren't going to jump past a bunch of grounds and into a +12v system several inches away.

80vac is a contact short. You could slice the insulation and it wouldn't short to anything. So I'm calling bs on the stator wiring theory.



I told you a low impedance on the low side of the coil could cause an overcurrent condition on the transistors in the cdi. Any circuit trouble on the output of the transistors can overload them. The cdi is fed by a 30 amp fuse so the transistors are not suitably protected.


I'm a master electrician as well, and own a variable speed drives and controllers company. You work isn't lost on me. I'm just telling you that your electronics didn't get "zapped" by the high side of the coil.


You are making pretty vague speculations here that I feel aren't based in truths.
I just wanted to know if you'd care to divulge the name of your company ? Did you mean VSD or VFD ? I'm a commercial A/C tech.
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post #13 of 28 (permalink) Old 10-01-2019, 07:29 PM
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VSD and VFD are used interchangeably. To an electrician it's a VFD, to a layman it's a VSD.

My company is called laser it automation. We automate oil wells using vfds, controllers, and our own licensed Scada system. I do all the setup, programming and tech support, and my partner takes care of sales.


We work mostly with yaskawa, ge danfoss, and Toshiba drives, though I know my way around most of them. Yaskawas are my favorite though.
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post #14 of 28 (permalink) Old 10-01-2019, 08:14 PM
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...your [Wibbly] knowledge is excellent on these electronics...
+1 if Wibbly gives advice on RC-51 electrics/electronics, I listen to him more than all others but that's just me...

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post #15 of 28 (permalink) Old 10-01-2019, 09:11 PM Thread Starter
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Ill give a shout out to Wibbly as well! Im off to New York to visit family , when I get back Ill do some testing of the items that I can test. However, I believe that I found the source of the problem based on this thread. And since I live in California, when I get back Ill also go take the RC for a nice road test🤪... thanks again for your insight.
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post #16 of 28 (permalink) Old 10-02-2019, 03:53 PM
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VSD and VFD are used interchangeably. To an electrician it's a VFD, to a layman it's a VSD.

My company is called laser it automation. We automate oil wells using vfds, controllers, and our own licensed Scada system. I do all the setup, programming and tech support, and my partner takes care of sales.


We work mostly with yaskawa, ge danfoss, and Toshiba drives, though I know my way around most of them. Yaskawas are my favorite though.
Variable Speed Drives vary voltage , Variable Frequency Drives vary pulse width.
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post #17 of 28 (permalink) Old 10-02-2019, 04:03 PM
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Variable Speed Drives vary voltage , Variable Frequency Drives vary pulse width.

no.... not quite.


a VSD just refers to a drive that changes the speed of a motor. if you are using a VSD in a dc application then it would vary voltage, yes. however a VSD in an AC application is a VFD. it's the same thing. VSD is just a name, it doesn't refer to anything specifically.


if you vary voltage on an AC motor it doesn't change the speed, it just changes the torque.


if you vary pulse widths on a VFD you are only changing voltage, this doesn't change speed either, only torque.



the output from a VFD is a PWM where the pulse width determines output voltage, and the rate at which the pulses widen, then narrow, then invert, then widen, then narrow, then invert is the frequency. for each positive and negative portion of the sinwave there are a number of pulses, starting very narrow and working wider until they narrow back down again, the widths of these pulses are determined by the commanded output voltage of the drive. higher voltage = wider pulses on average, though they still ramp up and down in width. each of these pulses is full bus voltage (in a single level drive). the inductive reactance of the motor windings smooth these pwms creating a sinusoidal current waveform in the motor. you can also use a reactor on the load side of the drive to create a sinusoidal current waveform. the carrier frequency determines how many of these pulses there are. the rate at which the pulses narrow and widen, then inverse determines the frequency and motor speed. the width of the pulses themselves only changes the voltage.


VFDs (and VSDs in AC applications) both vary frequency AND voltage to maintain constant torque in the motor. this can be done either by a fixed VF ratio (ie a 480v/60hz motor would be 8v/hz), or using vector control (open loop or flux vector using encoder feedback).
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Last edited by Wibbly; 10-02-2019 at 04:12 PM.
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post #18 of 28 (permalink) Old 10-02-2019, 04:17 PM
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In a DC drive you can either use pwm via transistors and Change pulse widths at your carrier frequency (led controllers do this too) to adjust DC voltage (assuming you have a DC input)

or you can use SCRs from an AC input and vary the firing angle on the gates to change DC voltage. SCRs need filtering circuits on the output due to unstable bus voltages.
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post #19 of 28 (permalink) Old 10-02-2019, 09:45 PM
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Originally Posted by Wibbly View Post
no.... not quite.
...
VFDs (and VSDs in AC applications) both vary frequency AND voltage to maintain constant torque in the motor. this can be done either by a fixed VF ratio (ie a 480v/60hz motor would be 8v/hz), or using vector control (open loop or flux vector using encoder feedback).
Now you're just showing off.
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post #20 of 28 (permalink) Old 10-02-2019, 10:24 PM
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Sorry. I'm pretty passionate about drives. It's literally all I do haha.

Need to build an electric bike one of these days.
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