A Project that was working, then stopped

[Drew23]

Hi,
First of all I must explain why my posting came to be on this site, I was looking on the internet for a forum that could help with a project on mine, that had stopped working.
Which has a 24 volt DC motor, as part of the set up, I saw a posting on the site from someone who was having problems with a 24 volt DC motor, so that how I came to register on the electrician’s forum.

The project consists of a 600W AC to DC converter 230V TO 24V 25-30A power switch transformer, a 10-50V 40A DC Motor Speed control PWM HHO RC controller 12V 24V, and a 350W 24 volt D.C motor, rated current 18.7A.
There is a pulley on the shaft of the motor that can be connected to another pulley situated on a drive shaft, with a drive belt, on this shaft is also a fly wheel, and a large pulley, which is not attached to anything at the moment.

The speed controller has developed a fault where the current flows through the circuitry by passing the on and off speed control switch, so that when you turn the power on, the motor starts spinning.

Before the problem had accrued I had done tests runs of all the electronic’s, and electric motor, with out a drive belt being attached between the two pulleys. Varying the speed over a five minute test run, and there were know problem.

Next I connected the drive belt between the two pulleys, started spinning the flywheel by hand, (so that the motor did not have its dead weight to contend with when it started spinning) then turned the speed controller on, and set it at a quarter of a turn. Ran it for five minutes, know problems.

Did exactly the same again, but this time I set the speed controller to half a turn, it ran for 4 minutes before the motor lost power, and everything started slowing down, and stopped rotating.

I tested the AC-DC converter that works O.K, I tested the motor, and that works O.K

Any suggestion on what might have caused the damaging to the speed controller, would be greatly appreciated.
I did wonder whether the flywheel momentum could have build up, so that it ended up spinning faster than the speed controller, was set for the electric motor to rotate at. So that the electric motor was forced to spin faster, with out the current to feed it, to do this speed, but this is just hypothesising on my part.

Any thoughts anyone has on what has happened would be much appreciated, and what to do to stop it happening.

 

[DPG]

Welcome to the forum!

Is the speed controller module a decent quality one, or an ebay special?

 

[Drew23]

Welcome to the forum!

Is the speed controller module a decent quality one, or an ebay special?

Hi, Thank you for you welcome, and thank you for your reply to my thread, I did buy it on ebay, it looks a quality part, not cheap and tacky. But I am not an expert on speed controllers.

Everything was going alright with the tests, until I did the half speed test, and the flywheel really started to rotate, and four minutes into the test, that when everything went pear shaped.

 

[Lucien Nunes]

When a permanent-magnet DC motor is driven mechanically, e.g. by the momentum in the flywheel, it works as a generator. It will generate approximately the same DC voltage as it took to drive it at that speed as a motor. There is no reason for anything to malfunction when it was spinning no faster as a generator than it did as a motor, because the voltage won't exceed whatever level the controller was able to give it to get it up to that speed.

The next question is how many quadrants the controller can work in, i.e. whether it is able to brake the motor to a standstill as you turn the speed control down, or whether it just lets the motor freewheel and come to rest by itself. If it is a four-quadrant control with braking capability, was this configured correctly with any necessary external resistor connected?

Can you post a link to the controller? My hunch is we are going to find it simply failed and there is nothing in particular you did wrongly, but where there is a flywheel involved we should clarify what will happen in those braking quadrants.

 

[Drew23]

Thank you for your reply to my Thread, The flywheel is free moving, when the speed controller is turned off, everything then slow's down, and stops. I will send you the information regarding the speed controller, that I purchased on ebay. Once I have figured out, why the file I down loaded, won't allow me to click, and attach the file, I am afraid to say I am not a wiz kid on the computer, (older generation)

 

[Drew23]

When a permanent-magnet DC motor is driven mechanically, e.g. by the momentum in the flywheel, it works as a generator. It will generate approximately the same DC voltage as it took to drive it at that speed as a motor. There is no reason for anything to malfunction when it was spinning no faster as a generator than it did as a motor, because the voltage won't exceed whatever level the controller was able to give it to get it up to that speed.

The next question is how many quadrants the controller can work in, i.e. whether it is able to brake the motor to a standstill as you turn the speed control down, or whether it just lets the motor freewheel and come to rest by itself. If it is a four-quadrant control with braking capability, was this configured correctly with any necessary external resistor connected?

Can you post a link to the controller? My hunch is we are going to find it simply failed and there is nothing in particular you did wrongly, but where there is a flywheel involved we should clarify what will happen in those braking quadrants.

Did not have any success with sending you the file. But if you go on ebay, and type in 10-50 40A DC Motor Speed Control, it will take you to the page, (I typed this into the search box, to check that it went to the right page, and it did. I bought the second from the top £11.99) the seller name and number are Yevtte (6934)
just so you know you have clicked on the right speed controller. There is quite a lot of detailed information.

 

[Lucien Nunes]

I found it. There's no technical info but we can see from the picture of the PCB that it's a simple single PWM with five output transistors in parallel and a catch diode. This only operates the motor in quadrant 1 i.e. there's no braking and no reversing. When you turn the speed down the motor will coast down on the flywheel until it reaches the new speed. What I can't see from the view of the board is how it will behave if the power supply is disconnected or shorted while the motor is regenerating from the flywheel. It might not like that, although you said that the motor stopped while running so presumably just by itself, not because you powered it down.

So I've no clues as to why yours failed, other than the price of the unit. These low-cost modules are often of good quality in themselves, but they rely on parts bought at rock bottom prices that can sometimes let them down. For example, I used to buy a particular voltage regulator module that was ridiculously cheap but was perfectly satisfactory except that they turned up with a motley assortment of no-brand capacitors, some of which were OK but some of which were rubbish. I always replaced them with good quality parts before use and never had any failures because the rest of the module was good.

I'm confused as to what happens when you power it up now... does the motor run up to max speed or is it dead? The most common failure mode in a controller of this sort is shorted output transistors which will make it give 100% output. Do you have a multimeter and experience using it, so that we can test them and discover if this is the failure mode in your module?

 

[Drew23]

I found it. There's no technical info but we can see from the picture of the PCB that it's a simple single PWM with five output transistors in parallel and a catch diode. This only operates the motor in quadrant 1 i.e. there's no braking and no reversing. When you turn the speed down the motor will coast down on the flywheel until it reaches the new speed. What I can't see from the view of the board is how it will behave if the power supply is disconnected or shorted while the motor is regenerating from the flywheel. It might not like that, although you said that the motor stopped while running so presumably just by itself, not because you powered it down.

So I've no clues as to why yours failed, other than the price of the unit. These low-cost modules are often of good quality in themselves, but they rely on parts bought at rock bottom prices that can sometimes let them down. For example, I used to buy a particular voltage regulator module that was ridiculously cheap but was perfectly satisfactory except that they turned up with a motley assortment of no-brand capacitors, some of which were OK but some of which were rubbish. I always replaced them with good quality parts before use and never had any failures because the rest of the module was good.

I'm confused as to what happens when you power it up now... does the motor run up to max speed or is it dead? The most common failure mode in a controller of this sort is shorted output transistors which will make it give 100% output. Do you have a multimeter and experience using it, so that we can test them and discover if this is the failure mode in your module?

Thank you very much for your very informative reply to my Thread, and I greatly appreciate you taking the time and trouble, in trying to solve my problem. I will reply to your question's in your thread, with the information you asked for tomorrow, with a lot more back ground information as well.

 

[Drew23]

I found it. There's no technical info but we can see from the picture of the PCB that it's a simple single PWM with five output transistors in parallel and a catch diode. This only operates the motor in quadrant 1 i.e. there's no braking and no reversing. When you turn the speed down the motor will coast down on the flywheel until it reaches the new speed. What I can't see from the view of the board is how it will behave if the power supply is disconnected or shorted while the motor is regenerating from the flywheel. It might not like that, although you said that the motor stopped while running so presumably just by itself, not because you powered it down.

So I've no clues as to why yours failed, other than the price of the unit. These low-cost modules are often of good quality in themselves, but they rely on parts bought at rock bottom prices that can sometimes let them down. For example, I used to buy a particular voltage regulator module that was ridiculously cheap but was perfectly satisfactory except that they turned up with a motley assortment of no-brand capacitors, some of which were OK but some of which were rubbish. I always replaced them with good quality parts before use and never had any failures because the rest of the module was good.

I'm confused as to what happens when you power it up now... does the motor run up to max speed or is it dead? The most common failure mode in a controller of this sort is shorted output transistors which will make it give 100% output. Do you have a multimeter and experience using it, so that we can test them and discover if this is the failure mode in your module?

I have included more information on what happened after the motor stopped, and everything slowed down.

The first thing I noticed was that the green L.E.D's on the converter’s were flashing, normally they just glowed.
I turned the power off, and left it for 10 minutes, then switch the power back on, the L.E.D started flashing, and the other thing was that the electric motor pulley was twitching, when I touched the drive belt, you could feel the pulley pulsing, but not spinning. I turned the power off, and dismantled everything.

I first tested the 24 volt D.C motor by joining two 12 volt batteries together, and connected an isolation switch, wired the motor to the switch, turned it on, and the motor ran O.K at full speed.

I then wired in the speed controller, through the isolation switch, and then connected the motor to the speed controller. I made sure that the speed controller control knob was in the off position. Then turned the isolation switch on, the motor started spinning at full speed!, and I had not even turned the speed controller on!.
I then switch the speed controller on, but it did not effect the spinning of the motor, I turning the knob to full speed, then down to low speed. But it did not effect the speed of the motor, and when I switch the speed controller off, the motor just kept spinning at full speed! again, until I turned the isolation switch off.

Also I noted when I tested the speed controller there was a slight plastic burn’t smell, I noted that one of the six power Transistors mounted on heat sinks, the black ceramic, if that is what it is made from, had separated from its backing and you can see a copper square with another square of something, it looks like metal on top of that.

With the voltage converter now disconnected from the motor, and speed controller. I turned on the power. The green L.E.D's slowly lit up, and just glowed as they had done before, when everything was working O.K (not flashing when everything stopped) I checked the out going voltage, and it was 24 volts D.C

I then wired the motor directly to the voltage converter, turned on the power, the green L.E.D lit up, the motor made a pulsing sound a couple of times when it first started spinning but when the motor went to full speed, that stopped, I left it running for a couple of minutes, before I switched it off, where again it made a pulsing sound a couple of times before the motor stopped spinning.

So it looks like that the speed controller has a fault on it now, and the circuitry on the board has been damage in some way by the test I had carried out. letting the current by pass the switch.

When in your reply you mentioned about the circuit boards, and the fact that manufactures will use the cheapest components they can source.
I did go on the internet and search for speed controllers for sell U.K, and found a company that sold different types, and noted that one that I looked at, had over current protection.
The voltage converters I purchased, I did so because they had over load, over current, short circuit, & temperature protection. I mention this also because when everything stopped on the last test, that is when the LED’s that normally just glowed, started flashing, and also the fact that the speed controller was not advertised as having any protection.

From your reply to my threads, you obviously have a lot of knowledge of motors, speed controller and electronics, and I have gained a lot more knowledge from what you have told me of speed controller’s.

I personally have a very basic knowledge, I can identify most electronic components, and what there job is with in a circuit board, I have a few books on how to constructed your own basic electronic projects, and have made a few of them, so I have experience of soldered components onto a circuit board, and yes I do own a multimeter, my experience with that has been for testing for voltage

Before your last reply thread, where you mention about the quality of the components used on some of the circuit boards you have purchased.
I had purchased another of these speed controllers, as I wanted to will carry out the same test but this time will only go as far as the quarter of a turn of the speed controller, and when I switch the speed controller on I will increase the speed very slowly until, I get to the quarter of a turn, and do a five minute test.