In-Rush


	In-Rush Current Protection


	The excellent magnetic properties of Toroidal Transformers can occasionally lead to high in-rush current when turned on. The duration of the inrush current is normally less than 10 ms and does not cause any problems in the low power range. For larger Toroidal Transformers we recommend the following protection.

Transformer Rating	Recommended Protection
15 VA - 300 VA	None
300 VA - 1.0 kVA	Slow blow fuse
1.0 kVA - 2.0 kVA	Small external resistor in the primary circuit
2.0 kVA - 10.0 kVA	NTC thermistor or soft start circuitry

POWERTRONIX In-Rush Current Modules are designed for use with POWERTRONIX Toroidal Power Transformers and POWERTRONIX AC
power units, such as the MIU. These modules are included with all of our components and systems
with power ratings greater than 2.0 kVA. By the use of these modules, high surge currents - caused by low line impedance - can be limited to a maximum of only 60 amperes peak under any line and load condition. This will prevent nuisance tripping of circuit breakers and limit peak current stresses on rectifiers and switches. The duration of the in-rush current is normally less than 10 ms and does not cause any problems in the low power range. Custom OEM versions are also available.

Powertronix . 1120 Chess Drive, Foster City, CA 94404
Tel: (650) 345-6800 . Fax: (650) 345-7240