Help With AC Connector for Induction Heating Unit

Hey everyone,

I'm working on an application for an induction heating circuit. I need to find a suitable three-connection plug / jack for a connection between the capacitors and the working coil.

There is one positive and two ground connections & the resonating frequency is about 225 khz. It also draws 5 to 6 amps, max. I was wondering if someone could tell me what the best-suited (& most compact) connector would be for this purpose. Here are a few preferences:
- Compact shape (1/2" diameter or less)
- $3 each or less (planning on ordering 50-100)
- 6 amps (ac) rating

I tried a 3.5mm stereo jack (3 connections) just for the hell of it, but I’m assuming the connections aren’t robust enough to handle the current. My next thought was possibly a mini xlr plug, but the ones I’ve seen are a little bulkier than I'd like (larger than .5" diameter & a little long), and somewhat expensive (more than $3). Any other ideas?

Thanks in advance.

Most popular plug is Mate-N-Lock cheap 10A

To work for 6A 225 kHz, connector and cable must be skin-effect derated (presuming you are not using litz wire). As a first guess, I would target to the 20-30A range.

I always wondered why power connectors were not given specs for frequency.

sd= k/√f
k=65.4mm for copper, 133mm for brass

- sd=65.4/ √225000=0.13mm or 0.26mm max AWG30 Cu wire
- sd=133/ √225000=0.28mm for brass contact base or 0.56mm thick.
reference on sd

This typical pin for the 0.25" pitch housing uses 0.012" brass stock or 0.3mm with tin over nickel plating, which is good for the skin depth at 225kHz, but not the AWG16 wire.

Litz wire is essential at this relatively high frequency for induction heater wire, to minimize self heating losses. There are many combinations of bunches x strands x AWG for every size.

What power are you feeding the work coil, with out any metal in the work coil, there could be very high voltages due to resonant tuning.
Frank

SunnySkyguy said:

Most popular plug is Mate-N-Lock cheap 10A

Click to expand...

Awesome suggestion. The only thing (that I should've also mentioned in my OP) is that the connector needs to be aesthetically pleasing, as I'm working on a prototype for a consumer appliance. That plug looks like it would’ve been perfect if it was just for a personal project.

FvM said:

To work for 6A 225 kHz, connector and cable must be skin-effect derated (presuming you are not using litz wire). As a first guess, I would target to the 20-30A range.

Click to expand...

Good call.. I was actually planning on getting some litz wire (420/42 – type 2). That’s one other thing I’m a little confused about though – I know that cable needs to be derated when used with high frequency AC, but I’ve never read anything about connectors needing to be derated, when used with high frequency AC (now that I think about it, it makes sense though).. If I use litz wire, do I still need to derate the connector, regardless?

SunnySkyguy said:

I always wondered why power connectors were not given specs for frequency.

sd= k/√f
k=65.4mm for copper, 133mm for brass

- sd=65.4/ √225000=0.13mm or 0.26mm max AWG30 Cu wire
- sd=133/ √225000=0.28mm for brass contact base or 0.56mm thick.
reference on sd

This typical pin for the 0.25" pitch housing uses 0.012" brass stock or 0.3mm with tin over nickel plating, which is good for the skin depth at 225kHz, but not the AWG16 wire.

Litz wire is essential at this relatively high frequency for induction heater wire, to minimize self heating losses. There are many combinations of bunches x strands x AWG for every size.

Click to expand...

I was planning on buying some type 2, 420/42 litz wire – does that seem suitable to you? 42 gauge is supposed to be best for frequencies of 200-350khz and 420/42 equates to 16 AWG. Do you think I could get away with using a smaller-diameter litz wire such as 270/42 (equal to 18AWG) for my application?

chuckey said:

What power are you feeding the work coil, with out any metal in the work coil, there could be very high voltages due to resonant tuning.
Frank

Click to expand...

The PSU I’m using is rated at 12V / 6A. That’s interesting – when I measured the voltage, my multimeter only recorded 1.3V. I think I remember reading that induction heaters can generate dangerously high voltages though.

18 AWG Conductor Ampacity of based on copper conductors with 75°C or higher insulation in an ambient temperature of 30°C and for flat wires not wound. Thus 18 AWG will overheat.

TE has lots of pretty connectors in MateNLok catalog online