DC Drive, Heat Required to Kick Start

Sounds like there is a thermal overload sensor/circuit which is malfunctioning.

Hi MJB you have a valid point here but appling heat would surely increase the problem.

Cheers

Joe

There is a usually a sensor (thermistor) mounted to the heat sink which could be going open-circuit causing the drive to "think" it is too hot. Applying some heat causes expansion which closes the connection allowing the correct thermistor signal to enable the drive. Best wishes.

Is there a NTC thermistor before the bulk capacitors for inrush current protection? Check it and if OK try heating individual parts of your assembly to isolate fault. Possibly a power semiconductor internal failure. Or a capacitor developing hi ESR. Not that uncommon situation if you deal with ag(e)ing equipment. S.M.

Hi Simple Mind, I do understand where you are comming from but the unit dosent have any bulk storage capactors.

So there is no inrush current, also when we apply the heat the drive is not in a run mode, it is stationery.

Cheers

Joe

Now here IS an opportunity to use your heat gun to trace this heat sensitive problem.

I suspect it may be a faulty or out of tolerance component, especially if you think you have eliminated any dry joints. Other things to look out for may be the drive transistors (or similar) connected to the heatsink.

Try removing the heatsink and running the Drive under light load while carefully applying heat to as few components at a time and see if you can narrow it down to a single component.

I have a similar problem with a small induction motor driving the blower in my space heater - in my case it is because the unit is old, and situated in a 'warm' environment and the grease which is also old is very sticky until it warms up a little, and since the induction motor has low torque at stall it sits there until it warms up a little with the current until the 'stiction' decreases to below the stall torque.

This however is unlikely to be your problem - I mention it only for everyone's interest.....

Hi Jack, that is exactly what I did use

But the point is after appling the heat even if the drive is not running, the drive is ok to operate at any time as long as the power is applied.

Cheers

Joe

Interesting choice. I immediately wondered if rapidly cooling down online components might actually cause damage that wasn't already part of the problem? I would think it would.

Hi David that is not a bad answer, it is the oppsite to what we would usally do isn't it, but it is a good idea

Cheers

Joe

Hi JRaef to be honest I don't know if it is SCR Based, it is pretty old so I would think not, you could be right about the connection between the heat sinks though, the machine mech wise is good but the product that they are packing is icing sugar and this is all through the control system, the whole system requires a complete overhaul.

Cheers

Joe

Sounds like an intermittant open connection in the control circuit. Check for any heat sink mounted components like overtemp thermostats.

Hi All, I have had a meeting with the customer (victim) today, he has purchased a new Haysen Packer (second hand ) and is having this machine overhauled to replace the existing packer, then he wants me to upgrade the existing packer with a complete new control system. He likes this packer because it is built like a brick sh** house, it is mech robust. So we have the project to up grade all the electrics including PLC, drives and Electrical drawings, motors will be overhauled and the problem DC drive will be replaced.

I would like to thank all CR4 contributors that have given their time to respond to this issue, but after the reconditioning I will have another look at the drive (when I-If have time) and report my findings.

Also appoliges for not responding to you coments earlier, I have had a busy week so far with other problems on other machines.

Thanks Again contributers, I will post this and then add my votes.

Best Regards

Joe Sparky

Hi Joe, I'm interested to know what the fault turns out to be.

I agree with the idea of cleaning the drive board

I normally look over my boards with a hand held microscope

Another thing to check is the possibility of hairline cracks in circuit board tracks, or

Sometimes fuses disconnect at one end due to stress from thermal cycling, are there any on the board?

Also resistors that run hot (blackend from heat) may look ok on the board but fall apart when you desolder them.

Dave

Dear,

I have come across similar problems earlier, it may be due to dirty PCB, humidity not enabling the drive. Cleaning & drying up PCB by heating, solved the problem.