Victron Multiplus 24/3000/70 and Waveform

DIY
1

I have a V3000 MP 1 and a surfeit of solar energy during the day. So I thought I could use a power reducer to reduce the input power of a 3kW immersion heater in my hot water tank, so I can heat with around 750W from solar.

I bought one of these - Cruise control 230 V, cruise control 230 V, motor 10 A 4000 W | voltage regulator SCR, dimmer, European plug, cruise control, motor use, with protection : Amazon.fr: Industrial & Scientific

The ingredients of the controller are a BTA 41 1000B 40A standard TRIAC and a couple of MPR 275 X2 smoothing capacitors. The BTA changes the phase to achieve the voltage adjustment.

It works - at an output of AC 70v, the DC draw is around 30A at 28v which is perfect.

But there is a light buzz from the Victron as well as the normal cooling fan. I am wondering if this buzz is detrimental in the long term. I assume it is feedback/the harmonics on the AC system making the transformer buzz??

I have attached three oscilloscope traces - the normal output from the V3000,

20260815 V3000_1
20260815 V3000_1320×240 32.2 KB

one of the AC system with the controller in operation

20260902 AC System
20260902 AC System320×240 33.6 KB

and the other immediately on the output of the controller.

20260902 Post Regulator
20260902 Post Regulator320×240 32.7 KB

There are more harmonics than usual on both traces.

The alternative device to use is an UNITED AUTOMATION BVR-25 POWER REGULATOR, 25A - BVR-25 Datasheet | United automation The BVR doesn’t change phase but is more ££££.

But now having found this topic - Optimal dumpload regulation from a point of view of a Multiplus

a Crydom PMP2425W would probably do the trick, but I would like to know more about the control method??

2

rather than trying to “dim” an immersion heater, with consequential degradation of waveforms, why not:-

  1. Turn it on for 10 mins, then off for 20? (could cause lack of system capacity…)

  2. Run it through a step down transformer, stepping down to 120V will give 1/4 power, say ~500W. This will maintain the resistive load.

3

Thanks. Immersion is 3kW, inverter only 3000VA.

Transformer more interesting.

A BVR-25, which maintains the waveform is probably better. Or a custom immersion with dual elements.

4

Alternative would be to use a dedicated inverter or Variable Speed Drive to power the heater. Dedicated inverter can be 120V, and you can trim the ac voltage a bit to get the desired load.

5

Thanks. It occurred to me that a VFD might be the solution without introducing harmonics that affects other electrical items.

I’ve successfully used a 1ph to 3ph 1.5kW VFD to drive my anchor winch motor.

I’ve found this 1ph to 1ph VFD - Wattive Frequency Inverter for VFD Motor, Frequency Converter 2.2kW Single Phase Input 220V Output Single Phase 220V CNC Frequency Converter with 2m Extension Cable : Amazon.fr: Industrial & Scientific

I guess reducing the output frequency reduces the power??

6

With a heater it’s more important to control the voltage than the frequency. For a motor, the voltage may also be reduced with frequency, but this relationship will depend on the motor requirement. You would have to look at the data sheet.