Lights blink when test firing an electric stapler

[Ibicycle]

We manufacture an electric stapler and test before final packaging. During the test firing of the new tools the florescent light in test booth blinks as well as the lights on other tables in the area. The other tables are on a different 110v circuit, but do share a neutral. There are three 110v circuits in this area. Fed by a three phase transformer. All outlets in the area are wired with 12 ga wire. Is there any type of filter or whatever to lessen the blinking lights in the same or other circuits?

[suemarkp]

The only thing I can think of would be a uninterruptable power supply (UPS) that constantly runs off the inverter (I think these are call full conversion UPS's??) and not the little cheapie APC ones for computers. How many amps does this stapler draw, and what are the peak amps? If you're pulling 30 to 50 amps through this line for a very short interval, that is going to cause noticable voltage drop on the neutral and hot conductors. Some of the lights, however, should be getting brighter and not dimmer when the stapler fires. This light flicker is common with motors when they first start up. I'm assuming your stapler is similar to a motor with a short duration high current impulse.

I think your best solution would be to use a dedicated circuit for the stapler that has no common circuit wires with other receptacles or lights. Should be much cheaper than an expensive UPS.

[Wgoodrich]

Another idea that I picked up on is that the common neutral are serving two hot wires of the same phase instead of opposite phases thus causing an overload of the neutral acting as a grounded leg not a true neutral. Easy to confirm. Votage test between the two hot wires being served by this common neutral. If you read zero volts then you have wired a multiwire circuit wrong needing to move one hot wire to the opposite phase. If your voltage test reads 240 volts then you are back to the previous reply.

Just an idea reading between the lines.

Wg

[AllanJ]

Is there a separate, smaller, 3 phase transformer for just that room, for example stepping down from 480 volts building-wide power to 110 volts? That could be undersized, resulting in additional voltage drops.

I would not expect a "main" transformer for the whole building to exhibit noticiable light-dimming voltage drops in this scenario.

[Mr T]

I take it these are not the $15 desktop staplers that do 5 pages? :musicus:

You are saying lights on a bench/booth.. Are the staplers that you are testing plugged into a outlet on the bench or directly into a wall? If on the bench what type of cord is going from the wall/power feed to the bench? Are the lights hooked up to this same outlet?

If the wiring to the bench is on the small side and you are testing a massive stapler that can do a hundred or more pages then you are gonna have a voltage dip. It's like running a power saw on a small extension cord and pulsing the switch. On some of the large staplers, I would even think that 50A is a low estimate of the inrush current when the stapler fires. At the college i went to in one of the computer labs (where it's supposed to be somewhat quiet) the stapler they had could staple plywood together. The first time someone uses it they jump when it fires.. It's not something i want to get my fingers caught in.

When a de energized solenoid is seen by a circuit, it is seen as a dead short kinda like a capacitor is. LOTS of current will flow for a split second. Once the coil starts to energize the current flow drops off significantly. I work on pinball games as a hobby.. Those solenoids run at 48V and draw less then a amp each, but they will often make my lights blink in the house when they fire.

I would guess that a power upgrade would be something to look into in the area. The inrush current was probably not taken into consideration when things were laid out. Is there another phase available to move the lights to? If your staplers are being powered by the bench, does plugging them directly into the power source for the room make any difference?