BT150 Thyristor equivalent(BT151) has just exploded !!!

[CDRIVE]

My friend this is not the way I trouble shoot. The period of hypothesis has expired. Answer these questions and or do what was asked of you.

https://www.electronicspoint.com/bt...-has-just-exploded-t262310p6.html#post1565408

One of the perks of getting old is crankiness is expected and accepted.

Chris

 

[Elecbegginner]

Hi again am back .

CDRIVE i have decided to return the card to the owner , i couldnt find the exact Thyristor's version , and i checked the parts of the card a number of times and it seems OK.

So now i decided to make my own AC motor speed variation card , i will make another thread about it to show you the steps of my work .

 

[CDRIVE]

You're not the owner?

Chris

 

[Elecbegginner]

lol no , am just the DELEGUE

 

[elebish]

Probably an "induction" motor. An scr is used to control the speed of the motor but the scr must be contolled by triggering the gate to turn on and then reverse biasing the scr or removing the voltage from the scr down below the holding current needed to turn it off. This will send pulsating dc to the motor which will act like ac. I suspect that the motor is bad or the circuit controlling the scr is defective. A triac will gate with either a neg or positive voltage and will allow current to flow in both directons. You might try replacing the pwm chip. Just guessing since I have no schematic to base my opinions on. Good luck! Ed.

 

[Elecbegginner]

Probably an "induction" motor. An scr is used to control the speed of the motor but the scr must be contolled by triggering the gate to turn on and then reverse biasing the scr or removing the voltage from the scr down below the holding current needed to turn it off. This will send pulsating dc to the motor which will act like ac. I suspect that the motor is bad or the circuit controlling the scr is defective. A triac will gate with either a neg or positive voltage and will allow current to flow in both directons. You might try replacing the pwm chip. Just guessing since I have no schematic to base my opinions on. Good luck! Ed.

Its an AC 220 V induction motor indeed and its working fine , i checked the circuit and all seems good and as I've already mentioned i need the exact same reference of thyristor as the original to make sure the problem is not from that at least.
But from what i understand , SCRs are not helping speed control , but just switching on or off , speed varies with respect to each speed circuitry (eg : resistors)

 

[CDRIVE]

TWIMC,

There are very few induction motor applications that lend themselves to satisfactory Thyristor slope trigger control. Ceiling fans are in this small category because their load is next to zip... Not much else.

Chris

 

[CDRIVE]

Its an AC 220 V induction motor indeed and its working fine ,

An SCR + 220VAC Induction Motor does not compute.

Chris

 

[Elecbegginner]

An SCR + 220VAC Induction Motor does not compute.

Chris

But in my case it is , i have 220 V AC motors ( one small and one a bit bigger )

 

[Elecbegginner]

Would this schematic work for motor speed contol ?

 

[CDRIVE]

That circuit employs a Triac and even Triac control finds limited use as I've described. What are the motors driving?

Chris

 

[Elecbegginner]

Thats the motor

Here is a similar machine wher the motor is used to move the malaxing hand .

 

[elebish]

OK guys i used another fresh thyristor with same code BT151 , but without any motor connected , i get output reading starting from 190V to 220V witch is not normal , because normally the motor should be running slow in the first speed at about 75 volts then raising till 220 volts witch is the maximum speed .

And when i connect the motor it does not turn even with 190 volts at output .

Do you guys have any idea ??

An scr allows current to flow one direction only when it is gated as long as the current flow through the scr is above the 'hold' current with voltages applied. It will stay on until it is reverse biased or until the voltages are removed from the scr. Hope this helps. Ed.

 

[elebish]

OK guys i used another fresh thyristor with same code BT151 , but without any motor connected , i get output reading starting from 190V to 220V witch is not normal , because normally the motor should be running slow in the first speed at about 75 volts then raising till 220 volts witch is the maximum speed .

And when i connect the motor it does not turn even with 190 volts at output .

Do you guys have any idea ??

You must remember that the duty cycle of the pulses going to the motor determine speed and torque. Ed.

 

[Elecbegginner]

You must remember that the duty cycle of the pulses going to the motor determine speed and torque. Ed.

Thanks , but do you think that a faulty SCR have some impact in output voltages or could it be caused by other things ?

 

[elebish]

Motor control

Thanks , but do you think that a faulty SCR have some impact in output voltages or could it be caused by other things ?

The scr will not change the output voltage by itself since it must be controlled. Some kind of control circuit must be employed to control the scr. Since most components are inexpensive, replace all ic's and check all resistors and caps. I would also check diodes including zener types. Always replace with same value parts. As I mentioned earlier, there could be a pwm ic used to control the duty cycle of the pulse going to the motor which controls the speed and torque of the motor. You will need a scope to check this. If you don't have one, just replace the ic. Without a schematic and possibly having this unit on my bench, I won't be able to give better info. Good luck. Ed.

 

[elebish]

I suspect a bad motor which can be checked with an ohm meter. If you have another motor similar to this one, bump the readings against one another. Ed.

 

[Elecbegginner]

I have another one and they are working the same way .
Anyways i did return the card , and at the moment i am planning to do my own speed control card actually , along with a variable power supply , and other stuff in the near futur .
BTW are you good in circuit modeling and design .???

 

[CDRIVE]

That does not look like an induction motor of any sort. My bet would be it's a Universal motor. Universal motors employ brushes, field windings and armature windings. They work equally well on AC or DC, hence the name. They are high torque in a small package.

After seeing the motor photo, which you should have posted a long time ago, the SCR makes sense now. It would explain why an SCR is controlling a mains powered motor. You can bet that there's also a rectifier bridge somewhere that powers the motor with full wave pulsating DC. On that note and if all the above is true. It's not PWM controlling the speed. It's simple (RC time constant) slope chopping.

Chris

 

[elebish]

That does not look like an induction motor of any sort. My bet would be it's a Universal motor. Universal motors employ brushes, field windings and armature windings. They work equally well on AC or DC, hence the name. They are high torque in a small package.

After seeing the motor photo, which you should have posted a long time ago, the SCR makes sense now. It would explain why an SCR is controlling a mains powered motor. You can bet that there's also a rectifier bridge somewhere that powers the motor with full wave pulsating DC. On that note and if all the above is true. It's not PWM controlling the speed. It's simple (RC time constant) slope chopping.

Chris

Possible, since pwm controlled motors are more expensive to make. I really can't tell since I don't have a schematic! Ed.