Voltage Collapse & Phase Converters - What You Need To Know
We recently had a customer who was retrofitting a sea can with heaters, and one pump to move fluid. Upon further inspection of this situation, the questions the customer presented were:
“Can I run a small motor on a large converter?”
“How do I prevent the voltage from collapsing when the equipment is running?”
The problem with running a small motor on a large converter - when it turns on - it’s not a big enough load to pull the voltages down on the rotary generator. Because the voltages don’t come down the small motor will be running on an excessively high and unbalanced voltage.
What does this mean for efficiency?
Not only is this inefficient, but the current draw on each line will be different as opposed to one balanced current. This will cause the overload to trip. There is a set period of time that the overload will allow the imbalance, however, the trip will always occur due to the lack of current balance.
To prevent this from happening, we can install a voltage level system on the converter, when it's idling we remove a certain percentage of the capacitors and put them on a contactor that is controlled by a voltage monitor.
This allows a third of the capacitors to be removed so when the little motor wants to operate, the voltages are in balance. When the big motor turns on, the voltage monitor sees a dip in voltage and tells the contactor to bring in the capacitors that were removed for the small motor, so that they are ready for use when the big motor is ready to operate.
Most converters are self-protecting, they have an overload device on the generator. It will just shut down and requires a restart.
Should this happen frequently, we recommend taking a deeper dive into the ampacity and voltage you require to ensure you have the proper electrical equipment in place.
A general rule to avoid any fuse pops or motor trips, is to look at the size of the converter and not run more amps on your machinery than the phase converter is rated for.
In short, if you’re experiencing frequent fuse pops, trips, or overloads - or you have any other questions, we’re happy to help you find the right equipment for your project, worksite and everything in between.
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