Article

A Zero Current Switch for Inductive Loads

Relays or contactors are often used to switch AC-powered inductive loads such as motors, valves or electro magnets. When the device is switched off, an arc can form across the relay contacts as they open. This leads to premature relay failure if measures are not taken to suppress the spark.

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Materials

100270-PCB.pdf

100270-11.zip

Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

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PCB

Download Gerber file: 100270-1.zip

Component list

Resistors
R1 = 100 Ohm
R2 = 2.2kOhm
R3,R4 = 47kOhm
R5 = 82kOhm 1%, 0.6W 350V (Vishay MRS25000C8202FCTOO)
R6 = 220Ohm
R7 = 180Ohm
R8 = 68Ohm
R9 = 22kOhm
Capacitors
C1,C3 = 10µF 100V 20%, pitch 2.5mm, diam. 6.3mm
C2 = 10µF 63V, axial, 10 x 4.5mm
Semiconductors
D1,D2 = 1N4004
D3 = 1N4007
D4 = BZX79-C13 (13V 05W)
B1 = WO6M, 600V 1.5A
T1 = IRG4BC3OKDPbF
T2..T5 = BC546A
IC1 = PC817 (see text)
Miscellaneous
PCB # 100270

Discussion (0 comments)

Colin55 2 years ago

What happened to the overlay on the PCB? I have not made a PCB in the last 40 years without an overlay containing all the component values so the module can be made by merely collecting the parts and sticking them on the board with glue. And I have over 260 different modules and this saves me remembering what parts were used on the module I designed 36 years ago. What a wonderful invention the overlay is. I pay $5.00 for 10 boards and I don't have to worry about remembering anything. And, of course I label every in/out terminal so I don't connect the output to the power supply and use a 240v supply when it should be 12v. And I don't use R1,R2, R3 because I cannot find R1 resistors in my junk box.

bko_01 2 years ago

Guess you have to buy the PCB with component overlay on the top side.

Colin55 2 years ago

A diode does not have a positive and negative lead. A diode ONLY has a cathode lead - - marked with "k" and this lead has a stripe on the diode. You have D1 & D1 = 1 amp And then you mark the zener diode with positive and negative but the cathode lead will have 13v on it !!

1 Comment(s)

Alain Dupont 2 years ago

Hi,
Any compatible replacement for the: IRG4BC3OKDPbF
may be a IKA10N65ET6XKSA2 from Infineon could do the job??
and as Colin55 said 'a shame to give such a PCB without overlay...'
The original article is from 2012.... was it really the start of PCB's?? ( I did my first one in 72, a frequency meter with nixie's from a french revue)
I'll take time to make my own PCB, and may be give it to you for publication, may be....

capture-decran-2022-11-26-a-203730.png (595kb)

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nophead 1 year ago

With inductive loads it is also good to switch them on at the top of the voltage sine wave when current would normally be zero. If they are switched on at the zero crossing the first cycle puts more current into the inductor than a normal cycle would. That can cause saturation and a heavy current surge.

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