Isolation Transformers
Every Irrigation Craft pump station has an isolation transformer.
Why ?
There are 6 reasons why Irrigation Craft ALWAYS provides the Isolation Transformer on every control panel:
1 - Isolation from Primary Source Electrical Transients
The isolation transformer does just that, it isolates the controls from the incoming power to the pump station. This isolation or gap reduces the intensity of incoming lightning surges and other sources of electrical transients. How is this gap accomplished? The controls obtain power from the primary side power by inductive coupling in the transformer, there is no wire connection between the controls and the primary power.
2 - No Neutral Wire (Less Vulnerable to Transients)
Because every Irrigation Craft control panel has this transformer, we then do not require a Neutral wire for our controls. Without a transformer Neutral is required to obtain 110 volts from the power source. This Neutral is a source of electrical transients. If Neutral is not in the control panel, there is one less source for transients to enter the control panel.
Irrigation Craft does not allow Neutral to enter the control panel, and there is no place to connect Neutral to the panel.
3 - No Neutral Wire (Not Vulnerable to Open Delta Wiring Errors)
This lack of a neutral wire is especially valuable on what are called Open Delta or High Leg power sources where there is one phase with a higher voltage potential to neutral. On open delta systems, if the high leg (220 volts to neutral) is connected incorrectly to the station then the pump controls and other components such as irrigation controllers will be damaged.
The open delta system 3 phase power supply provides Phases A, B, and C. Voltage potential between any of the three phases is 240 volts (nominal).
However, voltage potential between the three phases and neutral is not symmetrical. While two of the phases have 110 volt potentials to neutral, one of the phases has a 220 volt potential to neutral, and that phase is called the "High Leg". That is where the problem is. Power any device with the high leg and neutral, and the voltage is then 220 volts and not 110 volts as with the other two phases.
Irrigation Craft has seen thousands of dollars of damage to other equipment along side our equipment, and on our competitor's equipment simply because someone carelessly lost track of the open delta high leg, while our equipment has never been damaged by this problem.
Because Irrigation Craft never allows neutral into the control panel, and because we always "make our own control power" with a transformer, incorrectly wired Open Delta supply systems will not damage Irrigation Craft equipment.
4 - Safety - 24 Volt Supply for Controls, Sensors, & Pilot Controls
The transformer is a safety feature because it allows Irrigation Craft to provide 24 volts to all sensors, door mounted pilot controls, and outside sensors such as the: volute heat sensor and flow switch. This means that if a component shorts or leaks to ground, the only possible voltage a worker will feel is 24 volts when touching a metal pipe or other conductor inside the pump station.
A control panel door with 110 volts on the back side is dangerous to service technicians who may brush against the open door while working on the panel or as often happens, a gust of wind may blow the door against the workers arms.
Adjusting pressure switches is easy for service technicians because they know all Irrigation Craft sensors are powered with only 24 volts.
5 - Protects Customer's Added Equipment
Our customers frequently require additional equipment be installed on the pump station such as: irrigation controllers, small injection pumps, central control radios and modems, etc. The isolation transformer is part of a system that produces a protected source of power for these components, some of which are vulnerable to electrical transients.
6 - Protection against Condensation and Corrosion
Transformers are good protection against condensation. When warm moist air makes contact with cool objects, the air may cool sufficiently so that H20 gas in the air changes phases from a gas to liquid and is then deposited on the cool object.
Transformers are always slightly warm, and they warm up the space inside the electrical control panel, and therefore all components in the panel and the panel itself are kept at a temperature above ambient, thereby preventing condensation from occurring.
By preventing condensation in the control panel the transformer prevents corrosion and deterioration of electrical components.
This is the isolation transformer as installed on an Irrigation Craft pump control panel. This transformer is custom made for Irrigation Craft by General Electric and has the following features:
150 VA output provides sufficient power for all Irrigation Craft panels.
Multiple inputs allows the use of one transformer for all Irrigation Craft products, lowering costs and making support easier. This transformer has primary connections for 208, 240, and 480 volt inputs, while providing dual output: 110 volts for the contactors and 24 volts for the controls.
Finger safe wiring.
UL Listed
These transformers have excellent reliability which we attribute to excellent design and manufacturing techniques by General Electric on our behalf.
Above is a typical irrigation Craft wiring schematic for the isolation transformer.
The schematic shows that there is no wire connection between primary and secondary wiring. The secondary (low voltage) power is obtained from the primary power (high voltage) by inductive coupling due to the close proximity of the two coils of wire, across a metallic blanket that limits or isolates the amount of power let through that can occur when voltage transients occur.
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