Triac and opticalcoupler burnt while using for controling a 3 phase motor

Thread Starter

SNOWA

Joined Sep 22, 2021
3
Hi guys, we use the following circuit to control a 0.75KW(380VAC) 3-PH motor to turn on/turn off/turn reverse.
The JD_ON,MOTOR_IDR,TRIACT_ON are connected to the MCU STM32F103
U4: TBD62003AFWG(7channel sink type DMOS transistor array )
JD1, JD2, JD3: 16A 250V Relay
RELAY1: 8A 250V Relay
CN1: 380VAC input connector
CN2: 380VAC output connector
R4,R5,R6,R7,R8,R9: 2010 SMT resitor(3/4W)
Q1,Q2,Q3: ST BTA24-800BW
C5,C6,C7: 10KV 10NF MMKP82 CBB
R1,R2,R3: 5W Metal oxide film resistor
Turn-on timing: MOTOR DIR(base on the desired direction of the motor) >> delay 80 ms >> JD ON >>delay 80 ms >> TRIACT ON
Turn-off timing: TRIACT OFF >> delay 300ms >> JD OFF

It look works fine in our lab for controling a few motors. But while using in the customer enviroment(usually there will be around twenty devices working in same the time), it burnt the triac(sometimes even the relay and the opticalcoupler are damaged, contacts in RELAY1 are broke to be sticky) occationally.
So please give me some advices or point out the existing problems about the design.
circuit.jpg

2.jpg3.jpg
1.jpg
 

kaindub

Joined Oct 28, 2019
90
I would replace the optocouplers with non zero crossing ones. Three phase motors require three even phases to operate correctly.
Then see what happens
 

du00000001

Joined Nov 10, 2020
81
What is the short-circuit current of these motors?
When starting slowly, the start currents might exceed your PCB's/components' current carrying capabilities.
 

JDiaz

Joined Nov 4, 2019
7
I think I know why...follow below wiring:
Fwd: Rev:
x(u)L1=L1 connect to L3
y(v)L2=L2 connect to L2
z(w)L3=L3 connect to L1

That is the reason triac's burnt out..L1 is fixed and you are switching L2 and L3.
 

JDiaz

Joined Nov 4, 2019
7
Please send me an e-mail to <deleted> if this solved the problem.

Moderator edit: email address deleted to prevent spam.
 

Johnfoxwell

Joined May 23, 2021
4
Looking at the Motorola application data sheet for the MOC3083 (AN982) there are two things that can damage the circuitry.
The snubber values should be calculated for a particular motor's inductance. Otherwise the SCR can be switched ON by a high dV/dt value.
The triac must be capable of conducting six times the rated current when the thyristor is switched on.
 

Thread Starter

SNOWA

Joined Sep 22, 2021
3
What about the Ac source phases (L1,L2 & L3) ,do they are matching on motor connections?
I think the phase connections should not be the problem because some of the devices with same motor connection works fine in same project.
 

Thread Starter

SNOWA

Joined Sep 22, 2021
3
Looking at the Motorola application data sheet for the MOC3083 (AN982) there are two things that can damage the circuitry.
The snubber values should be calculated for a particular motor's inductance. Otherwise the SCR can be switched ON by a high dV/dt value.
The triac must be capable of conducting six times the rated current when the thyristor is switched on.
The BTA24-800BW is a three quadrant triac with high dV/dt value, the nominal currnet of the motor is about 1 A and will become 5 A in startup, 24A triac should be enough. The snubber calculation is so complicated, I just use a conventional values combination.
 

djsfantasi

Joined Apr 11, 2010
7,861
Please send me an e-mail to <deleted> if this solved the problem.
Posting an email address in the forum is frowned upon. It attracts scammers that scrape forums for such email addresses. It may be removed if found by a moderator.

Expect to do all communication on the forum. You can decide to be notified of thread updates by email.
 

du00000001

Joined Nov 10, 2020
81
Posting an email address in the forum is frowned upon. It attracts scammers that scrape forums for such email addresses. It may be removed if found by a moderator.

Expect to do all communication on the forum. You can decide to be notified of thread updates by email.
@JDiaz
You can send a PM within the forums: mouse-hover over the recipient's name (in one of his/her posts) and click "start conversation" when the pop-up appears.
 
Top