Knowledge hub
Motor starting, overloads, capacitors and inverters
Everything between the isolator and the motor terminals. Written by engineers who size these every day.
Why does my pump keep tripping? A diagnostic checklist
Overload, blockage, seal, cable or supply: a step-by-step way to find out why a pump trips, what each cause looks like at the panel, and what to do about it.
29 May 2026 · 5 min read
Why single phase motors need capacitors
Let's start with a simple fact - three-phase motors are better than single-phase motors. More torque, no capacitors, fewer complications. But a huge proportion of real-world applications only have single-phase power available, and single-phase motors can't start on a live and neutral alone. That's w
24 April 2026 · 4 min read
How to run a 3 phase motor on a single phase supply
If you've ever faced a situation where you've got single-phase power but need to run a three-phase motor—say, a pump in a remote water treatment site—you've likely looked at single-phase-in, three-phase-out inverters.
20 February 2026 · 5 min read
How to wire the control terminals on an Invertek Optidrive Eco (ODV-3)
The Invertek Optidrive Eco (ODV-3) is a popular choice for HVAC and pump applications across the UK. Whether you're controlling a fan motor or a borehole pump, getting the control wiring right is essential for reliable operation. This guide covers the control terminal layout, common configurations,
9 January 2026 · 4 min read
Motor starting methods: DOL, star/delta, soft start and inverter
When designing control panels, selecting the right motor starting method is a key decision that can affect cost, reliability, and long-term performance.
27 June 2025 · 4 min read
Star/Delta motor starting - why is it so misunderstood?
Star/Delta motor starting is a common method used to reduce the surge in current and torque during the starting of large motors. However, sometimes there can be errors when installing the starter and connecting the motor. The main problem with starting a large 3-phase motor direct online (DOL: from
14 February 2025 · 3 min read
Replacing failed inverters
Sometimes when the power to an inverter is turned off (power cut/maintenance/repair etc) the inverter won’t turn on again afterwards. What follows next is difficult explanations about why a perfectly working inverter has suddenly failed after the maintenance engineer worked on the equipment. Well he
31 January 2025 · 2 min read
Capacitor Sizes
What size capacitors does my pump need, and do they go in the panel? Capacitor sizes are one of the hardest pieces of information to find, so here is what you need and where it goes.
20 September 2024 · 3 min read
Inverters no longer break the bank!
There are many electric motor applications where an inverter (or variable speed drive/VSD) is better than fixed speed/direct on line, with price as the only drawback. Traditionally inverters have been too expensive for many uses, but as technology advances the price of inverters continues to fall w
5 July 2024 · 3 min read
Transformers: A Quick Guide
It’s common to have a transformer in a control panel, but what exactly are transformers, how do they work, and what are the different types used in control panels?
28 June 2024 · 4 min read
What's the full load current of the motor?
Every electrical engineer has needed to find out the full load current of a motor at one time or another, often to check what to set the overloads at or to size the MCB/fuse on the supply.
22 March 2024 · 1 min read
Relays - the things you always wondered
The humble relay in control panels is probably the component you're most likely to have worked with. But it's surprising how often some of its functions are misunderstood.
15 March 2024 · 4 min read
What you are doing wrong with overloads
Thermal overloads are an important part of motor protection. When too much current passes through the overload it changes the state of the relay, which in turn prevents the motor from running.
16 February 2024 · 2 min read
Why do stepping relays fail on pump control panels?
Every pump engineer up and down the country has replaced a stepping relay in a control panel. It's basically a rite of passage - you're not a pump engineer until you've done at least one stepping relay! Most carry a box of spares in the van, and that little box of stepping relays costs £00s. What
5 January 2024 · 2 min read
Got a project, or just need a quick answer?
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