VSD Brake Resistors – Why they matter
If you’re running Variable Speed Drives (VSDs), brake resistors are one of those components that either quietly do their job… or cause you headaches when they’re wrong.
So, what do they actually do?
When a motor slows down, it doesn’t just stop – it turns into a generator and pushes energy back into the drive. That energy has to go somewhere.
Without a brake resistor, that energy builds up in the drive and can trip it out on overvoltage.
A brake resistor takes that excess energy and safely burns it off as heat, letting your system slow down properly without nuisance trips.
Where we see them used
We’re dealing with these setups all the time across sites, especially where you’ve got:
- Pumps and conveyors that need controlled stopping
- High inertia loads
- Frequent start/stop processes
- Systems where downtime from trips isn’t an option
Where things usually go wrong
This is where experience actually matters.
On paper, brake resistors look simple. In reality, we regularly see:
- Resistors undersized for the actual duty
- Incorrect resistance values causing drive faults
- Poor placement – stuck somewhere with no ventilation
- No thermal protection wired in
All of these can lead to overheating, trips, or early failure.
What proper installation actually looks like
From recent jobs the EAS team have done, the key considerations to make sure you get it right are:
- Installing and positioning VSDs and associated gear properly on-site
- Running and dressing power, control, and thermistor cabling cleanly through MCCs and field cabinets
- Integrating filters, drives, and associated components so everything works as one system
- Testing motors, insulation, and cable integrity before energising
- Commissioning drives and confirming rotation, performance, and control with automation teams
- Labelling everything clearly so future maintenance isn’t a guessing game
EAS doesn’t just “fit a resistor” – we make sure the whole system behaves properly under real operating conditions.
The key thing to get right
Brake resistors need to be sized and selected based on how your system actually operates – not just motor size.
That includes:
- How fast you need to stop
- How often it happens
- The load involved
- Heat dissipation and environment
Miss that, and you’re back dealing with trips, downtime, or burnt-out gear.
Need a hand with your VSD setup?
If you’re not 100% sure your system is set up right – or you’re planning upgrades – it’s worth getting it checked properly.
We can:
- Assess whether you actually need a brake resistor
- Size and specify it correctly
- Install and integrate it with your VSD system
- Test and commission so it works first time
Get in touch with the team at EAS – we’ll make sure your drives run the way they should.
