Voltage regulator control panel MJ4A

04/01/2010 - Volume VI - Issue III

A complete line of voltage regulator accessories, headlined by the remarkable MJ-4A control Panel, and including communications modules, MJXplorer software (for configuring the settings), MJXtra software (used for upgrading firmware), and DNPConfigure (for custom DNP point maps).


Our firmware updates are free-of-charge to all customers. We are continuously adding new features and capabilities to satisfy your special requirements, and applications to make it easier to set up in the field. The latest instruction manuals are available as well. The MJXplorer software is a user friendly tool used not only for easily configuring the control panel but downloading useful information as well.


With a straight forward menu structure you can easily change control panel settings and choose metering information with a few simple steps. The configure settings can be saved for future use and are easy to load into other MF4A panels. Once downloaded the data logs can be saved into a spreadsheet for review.



  • Predictive maintenance algorithm based on decades of historical data with the Siemens tap changer design and validated through life-cycle tests in our tap changer test cell

  • One disconnection allows faster field replacement with no need to remove the control panel enclosure from its mounting. SIemens regulators provide the easiest, simplest retrofit in the industry. Smaller panel allows for easy retrofit onto Cooper, Howard, or GE.

  • Highly visible polarized LED display, even in the bright sunlight

  • Quick Key allows the customer to save up to 16 different data items without the need to scroll through the menus - no codes to remember.

  • 32 bit microprocessor

  • Voltage calculated from tap position for regulators with only one reference voltage, so that any regulator can be used in reverse power flow applications.

  • Drag hands reset key resets the drag hands on the position indicator as well as electronically tap position (min/max) on the control panel.

  • Built-in, selectable communications protocols so that no protocol conversion boards are required

  • Siemens Polarized Disconnect Switch (PDS) quick connect/disconnect to regulator

  •  Raise/lower indicator LED gives customer another indication if the regulator is raising or lowering

  • By-pass position location located at the power and tap control switches

  • Easy I/O access terminal block located on the back of the control panel

  • Fast Path Keys - frequently used keys located on the keypad on the control panel

  • MJXplorer software used to configure and acquire information instead of retrieving information manually

  • "Operator-friendly" keypad with tactile and audio feedback

  • Power and energy metering

  • Event logging interval logging

  • Harmonic analysis

  • Two way communication potential

  • Retrofits available.



The MJ-4A Control Panel uses the latest 32 bit microprocessor technology and a user friendly layout to provide the most advanced tap changer control. It features full power and energy monitoring, separate forward and reverse regulator settings, event and interval logging, date/ time stamping, multiple counters, alert information, and more. Standard local communications is provided via a Data Port on the front of the control panel while optional 2-way SCADA communications can be provided through RS232/485 or Fiber Optics connections utilizing popular embedded protocols.

The Communications Module is the interface used to connect the control to SCADA. WIth multimode fiber optic cable loop or star networks, RS232 multidrop configurations, and RS485 loop, star and open-ended configurations, the communications module is adaptable to any communications system. The Communications Module is easily retrofitted into existing installations or can be shipped on new orders.


Connect a control panel to your PC and update to the latest MJ-4A, MJ-XL, or MJ-X embedded software with our PC program, MJXtra. (Pre-1996 panels require a "flash" EEPROM to allow for MJXtra upgrades.


MJXplorer Communication Software (TM) is a Windows (TM) application designed to facilitate two-way communications between a PC and MJ-4A/MJ-X controls, either directly or through off-the-shelf modems. With the MJXplorer software, users can easily perform data extraction or continuous processing, control configuration, print reports, and transfer data to popular spreadsheets. The Voltage Regulator Simulator allows you to simulate system conditions for testing your Siemens Tap Changer Control Panels. The Simulator provides variable source volts, load volts and load current, lead, lag, and high power factor indication, an operation counter reset test button and a drag hand reset test button. Built into a rugged case, the Simulator is easy to bring into the field for on-site control testing.

Siemens Polarized Disconnect Switch (PDS) allows a quick and simple means to disconnect the control panel from the voltage regulator. Simply remove two wing nuts and pull the male half away. The PDS is specially designed for voltage regulators as it both removes voltage to the control panel and AUTOMATICALLY shorts out the CT upon disconnection. No special knife switches to throw or sequences to follow. The PDS can be disconnected while the voltage regulator is energized and regardless of tap position. Siemens voltage regulators and controls have been using this same PDS design for over 40 years, so replacing an old control takes a few minutes.


One disconnection allows faster field replacement with no need to remove the control panel enclosure from its mounting. Siemens regulators provide the easiest, simplest retrofit in the industry, including direct control interchangeability with all JFR regulators built since 1958.

In any typical electrical field distribution system, you will find equipment ranging in age from brand-new to 30, 40, or even 50 years old. Often, however, the older equipment is just as serviceable as the newer ones and only differs in the functionality of its controls.


Recently, regulator and tap changer controls have gone through the significant technological enhancements that have allowed users to accurately monitor and control their electrical systems from remote locations, and generally have better control over their business.


With Siemens accessories and retrofit kits, utilities can now economically elevate the performance of older regulators and tap changers to the state-of-the-art level. And Siemens MJ-4A control sets that standard for the industry.


Siemens MJ-4A control will give you the monitoring and data communication you need to succeed now and into the next century. And with new unique software packages, future upgrades are a snap.


The Voltage Regulator Retrofit Kit allows you to modernize your Cooper or GE regulators with the Siemens MJ-4a Tap Changer Control Panel. This easy-to-install kit, plus a new Siemens Control Panel (sold separately), creates new opportunities for advanced monitoring, communications, and control.