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Transformer Terms & Frequently Asked Questions

How does a Line Reactor compare to a Drive Isolation Transformer?
Term/Question:
How does a Line Reactor compare to a Drive Isolation Transformer?

Definition/Answer:
A line reactor can usually replace a drive isolation transformer when the intended purpose of the drive transformer is noise attenuation on the load or line circuit. Line reactors and drive isolation transformers are "two-way" devices: high frequency spikes or notched generated on either the line input or by the load output will be attenuated before reaching the load output or line input, respectively. In fact, a line reactor will typically do a better job of noise attenuation than a drive isolation transformer because it is a nearly pure inductive impedance device. The impedance of the drive isolation transformer is a function of the resistive and inductive impedance components. It is the inductive component of the impedance that plays the role in noise attenuation. A 5% impedance line reactor will typically have a greater inductive impedance component than a 5% impedance drive isolation transformer. An iron core line reactor may not be an acceptable substitute for a drive isolation transformer if the purpose of the device is to limit "fault currents" to the output circuit. An iron core line reactor will have a much higher fault current pass through characteristic than the comparable drive isolation transformer. However, for most systems 600 volts or less, this is typically a non-issue. If fault currents are an issue, air core line reactors may be utilized in the system. Air core line reactors will be larger and more expensive than iron core equivalents, but will still be less expensive and smaller than a drive isolation transformer. Air core line reactors are mostly used in systems that have line voltages higher than 15 KV.

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