EHC Mark II Power Supply Upgrade for GE EHC Mk II Turbine Control Systems

The manufacturer of the EHC MKII control system power supply recommends replacing the electrolytic capacitors in each of the power supplies every five years to assure reliable operation.

This presents several problems; today, these capacitors are in very limited supply and the job is time-consuming. In addition, the original EHC MKII control system power supplies are linear-type power supplies. Most power supply manufactures no longer produce this type of supply. Switching-type power supplies are recommended to replace the older type linear supplies. One of the first signs of an aging power supply is output voltage drift. Unfortunately, waiting until this voltage drift develops could be very expensive. For example, the change in voltage can have an undesirable effect on unit operation such as one or more servo-controlled turbine valves closing.

MD&A Control Systems Division has developed new retrofit upgrade power supplies to replace the existing EHC Mark II power supplies. We guarantee the EHC Mark II retrofit upgrade power supplies to be 100% interchangeable with the current power supplies. These power supplies require no wiring modifications and contain power modules which meet or exceed existing power supply specifications.

Circuit Design:

The EHC MKII control system requires four distinct DC power levels: +22VDC, -22VDC, 24VDC and 125VDC. MD&A retrofit upgrade power supplies require only two types of power supplies for the four power levels. The 22/24VDC power supply is used for the +22VDC, -22VDC and 24VDC power levels, while the 125VDC power supply is used exclusively for the 125VDC power level.

The new power supplies are the "switching" type except the 125 volt supply, which generate much less heat than the original "linear" power supplies, thereby requiring less cooling. This also reduces the power consumption of the EHC system.

Each MD&A Control Systems Division retrofit upgrade power supply has a 10 turn voltage adjust potentiometer with a scaled dial that makes calibration faster, easier and more accurate than the OEM power supplies.

Installation and Documentation:

The MD&A retrofit upgrade is guaranteed to be 100% interchangeable with the existing power supplies. Simply unplug the old power supply, remove it from the EHC cabinet, insert the MD&A Control Systems Division power supply in its place, plug it in and adjust the output voltage. That's all there is to it. No wiring changes and no modifications to the EHC cabinet are needed.

Each power supply includes detailed information about the power module and a complete set of circuit schematics showing all system interconnections. The power supply fits in the existing power supply location, requiring only minutes to install and calibrate.

For more information on MD&A Control Systems' products and services, please call (970) 224-2223 Ext. 140 or email: amcneill@mdaturbines.com