Posted By
Eva Otel

Why ”If it’s not broken, don’t fix it” no longer applies to power supplies in plating

Earlier this year, KraftPowercon’s Eva Otel, and power supply experts Tobias Nordström and Felipe Atti, ran a popular webinar for the general metal finishing industry. They looked at the importance of power conversion in achieving a consistently high metal plating quality, as well as how it can offer significant potential for saving time, money and energy.


The problem with older rectifiers

Most production managers are busy people, dealing with all the everyday challenges involved in manufacturing and finishing: productivity, maintenance, cost control, quality. If a piece of equipment is working, it’s unlikely to be a priority on their ‘to do’ list.

Understandably, many metal plating businesses are still using older rectifiers that are still going strong. But energy efficiency has not always been the priority it is now, and we see many rectifiers operating at only 70-80% efficiency – and we know that oversized rectifiers lead to larger energy bills. Older equipment can also deliver direct current with a lot of residual ripple, which is detrimental to output quality and leads to scrap and reworking.

It’s also worth remembering that output values on older rectifiers aren’t always accurate, which would explain why plating results are not always as good you might expect, and longer plating times are needed.

What’s the difference between SCR and SMPS performance?

If you were comparing a silicon-controlled rectifier (SCR) side by side with a switched-mode power supply (SMPS) rectifier, the voltage reading for both could be the same, but there you might see a significant difference in plating quality.

  • SCRs have a high-to-deep ripple in the current, with the current output reaching 0 for a fraction of a second. This causes thinner plating deposits and a milky or frosty appearance.
  • SMPS rectifiers have a much smoother ripple, which always ensures power availability is above the minimum required. This means that there is always enough voltage to keep the chemical process going to achieve a consistent deposit, while avoiding the burns that can happen if the current peaks too high. With a smoother ripple (no high peaks) you can increase the current to increase process speed without causing damage.

Watch the webinar to see why the power supply technology impacts finishing quality.

Learn more

Current control optimizes quality and performance

Even so, the output from a SMPS-type rectifier can still be sub-optimal, depending on how you control the power. If you’re using voltage control, you’ll know that the current density varies with the resistance in the plating bath, resulting in variable quality plating and increased plating time. It’s unpredictable. Too much ion transfer can also cause secondary reactions and resistance in the circuit, which is inefficient and can also burn the parts you are plating. And if you’ve seen current go down during a batch, that’s because voltage control is passive when the resistance in the circuit increases.

There is an alternative: using current control, you can control the process and ion transfer by securing a constant current density throughout. Current control saves time and optimises quality by making the process faster and more consistent

We compared a voltage controlled power supply with the experience of steering a car manually. Will the automatic cruise controlled car win the game?

Watch the webinar to see voltage control go head-to-head with current control. Who wins the ‘race’, and why?

Learn more

The advantages of working with a modular rectifier

Every rectifier running at less than its rated output is losing efficiency. So ideally, you want one that suits your particular need. With FlexKraft from KraftPowercon, the modular design means you don’t need to have an oversized rectifier, you can choose the number of modules you need to match the output you’re looking for. Each power module has a maximum of 600A/ 12V.


Easier scaling up (or down) and maintenance

Modularity also enables scalability, enabling you to grow production or downsize it as needed, and making installation, control and maintenance simple. You only need one critical spare part (a single module) for your entire range of rectifiers, regardless of size or manufacturing year – perfect for keeping your spares inventory costs and space to a minimum.


More reliability, less downtime

If the environment is really extremely tough, perhaps with extreme temperatures or a high risk of corrosion, then a water-cooled rectifier could be a good option for optimising conditions for the best rectifier performance, and keeping maintenance to a minimum. We also make a heat exchanger, CoolKraft, which means that there’s no need to have one specially designed and built for your rectifier.

Even if the rectification circuit in a module fails – because it’s the part that is always working with high load – with FlexKraft, you don’t have to go in and repair the module yourself (unless you really want to); you can quickly replace it with the spare we provide you with (it only takes about 15 minutes), and then send the one you’ve switched out to us for repair. That’s one of the great things about a modular system – you don’t have to worry about interruptions to production.

In fact, even if you don’t replace a single failed module, the rectifier will keep on working (just with reduced output) so your production line does not need to stop.


Reduce plating time

Ripple affects the quality and speed of plating. Replacing older rectifiers that have high ripple will improve plating speed and efficiency (FlexKraft runs at below, or around, 1% – we know this because we test every rectifier before it leaves our factory).

And of course, if you have a voltage control process (sometimes unpredictable) switching to current control will also make the process faster and more consistent

So what next?

Once you know that the quality and efficiency of your power supply can significantly affect your total cost of operations (as well as output quality), it’s worth looking into how much you could be saving. Our general metal finishing page features:

an online energy savings calculator (you don’t even need to give us your details to use it)

• a free white paper on current ripples and their impact on throwing power

• a video of the webinar this article is based on Even better, ask us about a free rectifier efficiency check, which will show you exactly where and how energy savings could be made.

Contact us today.

Even better, ask us about a free rectifier efficiency check, which will show you exactly where and how energy savings could be made.


Contact us today