Actually, the CWA version draws lower Line Amperes at Startup, then tapers off at a steady operating level - provided the Voltage at the Reactor Input stays within +/- 10%.
Constant Wattage Autotransformer setups typically draw apx. 80% of the stable operating Line Amperes at Startup.
There are Two other setups, which draw lower Starting Line Amperes -vs- Operating Line Amperes. These are:
Constant Wattage Isolated Transformer setup
(AKA: "CW" and "CWI")
Regulated Lag Isolated Transformer setup
(AKA: "REG-LAG" and "MAG-REG")
Both of these designs use a Tapped Primary Winding for multiple Input Voltage choices.
The CWI incorporates a single isolated secondary winding for Lamp operation.
Lamp regulation is performed via a Capacitor in series with the Lamp.
The REG-LAG setup has (2) Isolated Secondary Windings - One is connected to the Lamp, the other is a Tertiary Winding, connected to a Capacitor. This is used to regulate the Lamp Performance by regulating the Lamp's Current.
The Current Regulating device which draws higher Line Current at Startup, is the "High Reactance Autotransformer" (known as "HX-NPF" and "HX-HPF").
This setup is a CWA without a Series Capacitor connecting the Autotransformer (input) side, to the Reactor Coil (Choke).
As with the CWA, the Lamp is connected in series with the Reactor section, and the Input side's "COMMON".
Standard P.F. is nominal (50%). Improved P.F. is achieved by connecting a Capacitor across the Line Input at the Autotransformer section.
The standard basic Reactor version also draws higher Starting Current than the Operating Current level.
This type of Current Limiting "Auto-Regulator" device is simply a Reactor Coil in Series with the Lamp (no input Autotransformer section).
Without a Shunt Capacitor across the 2 Wire Line input, the Power Factor is 50% (200 VA drawn for a 100 Watt Lamp - 173 VARs bounced between the Reactor and the System Transformer)
Improved P.F. via Shunt Capacitor brings the P.F. to "High" (80%-90%).
It appears that the reason for the higher Starting Current, which tapers down to a lower Operating Current, would be the increasing Capacitive Reactance of the Operating Lamp / Arctube.
Looking at the complete Circuit, when the Assembly is first connected to an AC Source, the Generating Source sees the Reactor Coil only - as the Lamp is a Negative Resistance device.
The Reactor "uses" very little True Power (Wattage), and requires Magnetizing / Charging Power (Reactive Power), so the Reactor Coil draws a large Apparent Power (Voltamps), with an extremely low Power Factor.
As the Lamp's Arctube becomes more active - and the Lamp progresses to Operating level, the Lamp takes on more and more Capacitive Reactance - thereby storing more and more Reactive Power. As the XC increases, it "counteracts" against the XL, and in doing so the Reactive Power stablizes.
At stable Operating level, the connected Impedance (Z) reflected back to the Generating Device, appears to be comprised of nearly equal levels of Resistance and Reactance, and the VA Package impressed to the Load carries mostly True Power.
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!