What EV chargers do to an industrial supply
A fleet charger is not another motor. It is a large, non-linear load that can go from nothing to full draw in seconds, several times a shift, on a connection sized before anyone owned an electric vehicle.
Chargers are appearing on industrial premises across Pune faster than the connections behind them are being reviewed — a couple of AC points for staff, then a DC fast charger for the delivery fleet. Each is unremarkable on its own. Together they change what the incoming board does, and the first thing to notice is usually something else misbehaving.
A load profile nothing else on site has
A motor draws a large starting current for a second and then settles. A charger does the opposite: it ramps to full power in a few seconds and then holds it for forty minutes. A 60 kW DC charger is a sustained 60 kW that was not in the original load schedule, appearing without warning whenever a vehicle arrives.
On a connection with modest headroom, two chargers running together during a shift can take the site close to its contract demand — and demand charges are billed on the peak, not the average, so a fifteen-minute overlap can set the bill for the month.
Harmonics, and who feels them
Charger front ends are switch-mode rectifiers, and cheaper units inject meaningful current distortion back onto the board. That distortion does not stay where it is made. It heats the transformer, it heats the neutral, and it shows up as voltage distortion for everything else on the same supply.
The equipment that notices first is rarely the charger. It is the servo stabiliser hunting, the UPS reporting input distortion, or a VFD tripping on an over-voltage that nobody can reproduce.
| Symptom | Likely cause |
|---|---|
| Stabilizer hunting during charging windows | Voltage sag and recovery as the charger ramps |
| UPS transferring more often, no obvious outage | Input distortion or voltage dip outside its window |
| Neutral running warm on a three-phase board | Triplen harmonics summing in the neutral |
| Demand charges up without more production | Charger peaks coinciding with plant load |
| VFD nuisance trips | Voltage distortion on a shared supply |
Before the second charger goes in
Log the incoming board for a week with the first one running. You are looking for what the voltage does when a charge starts, and where the peak demand now lands. Both are cheaper to find now than after the connection has been upgraded.
Where this meets the UPS
A UPS on the same board sees the charger as supply degradation, because from its point of view that is what it is. A line-interactive unit will transfer; an online unit will absorb it in the rectifier and keep the battery out of it. On a site adding chargers, that difference stops being theoretical.
The cheaper intervention is usually separation rather than replacement. Chargers on their own feeder, from the same transformer but not the same board as sensitive equipment, removes most of the interaction for the cost of a cable run.
What we would ask before quoting anything
- Charger ratings, and whether they are AC or DC fast
- How many can run at once, realistically, not in theory
- Your sanctioned load and current peak demand
- What else shares the board — stabiliser, UPS, VFDs, welding
- Whether the transformer is yours or the DISCOM’s
Most of the time the answer is a separate feeder and a stabiliser sized for the real profile, not a bigger UPS. It is worth saying that plainly, because the bigger UPS is the easier thing to sell.
Questions we get asked
Anything not covered here, call us — most of it is faster to answer on the phone.
Do EV chargers cause power quality problems?
They can, and the effects usually appear on other equipment rather than the charger. The front end is a switch-mode rectifier that injects current distortion onto the board, and the fast ramp to full power produces voltage sag. What you notice first is typically a stabiliser hunting or a UPS transferring, not the charger misbehaving.
Can I put a charger on the same board as my UPS?
Physically yes; advisedly no. A separate feeder from the same transformer removes most of the interaction for the price of a cable run, and it is far cheaper than the alternatives once a problem is established. If it must share the board, an online UPS handles it considerably better than a line-interactive one.
Will chargers increase my demand charges?
Very likely, because demand is billed on the peak rather than the average. Two 60 kW chargers overlapping for fifteen minutes during a production peak can set the billed maximum for the whole month. Staggering charging outside the plant peak is often worth more than any equipment change.
Does a charger need its own stabilizer?
Usually not — chargers tolerate a wide input range by design. The stabiliser is more often needed by everything else, to hold the board steady against what the charger does to it. Which way round depends on the measurement, and a week of logging answers it definitively.