Advanced Cell Bypass for Variable Frequency Drives (VFDs)

Advanced cell bypass is patented technology at the Siemens Robicon drive. It allows the drive to continue operating in the unlikely event at the cell fault.

This feature is available on all Siemens Robicon drives. The unique perfect harmony topology makes it all possible.

When a drive is equipped with this feature a contact is present on the output if each other power cells. In the event of a fault the contact closes and isolates the output to the power cell.

With multiple power cells connected in series, the loss of one power cell leaves the remaining cells active, which allows the VFD to continue operating at a voltage a at least 80 percent, or up to 92 percent speed on a centrifugal load. This serial cell configuration is central to the bypass feature.

Watch the video below to learn more abut this technology.

Using Pneumatic Volume Boosters on Valve Systems

pneumatic volume booster
Pneumatic volume booster
A pneumatic air volume booster reproduces a low flow control signal with a higher regulated flow output pressure. It uses an unregulated input pressure to maintain a regulated output pressure under flowing and non-flowing conditions.

The regulated output of a pneumatic air volume booster can be any of the following:

      • A direct reproduction of the pneumatic control signal
      • A multiple of the pneumatic control signal
      • A fraction of the pneumatic control signal

Volume boosters are also used in conjunction with valve positioners on large control valve actuators to provide faster response than possible with the valve positioner alone. Deadband within the volume booster allows the positioner to make small incremental valve positioner changes in a highly stable manor without activating the volume booster valves.

The following video provides and in-depth understanding on how to use pneumatic volume boosters with valve actuator systems and how to optimize performance.

How Self Regulating Heating Cable Works

self regulating heat trace
Self regulating heat trace cable.
Self regulation heating cable in used in many industrial and commercial applications to maintain temperatures in pipes. vessels, and tanks. Whereas constant wattage cables produces the same power output irrespective of process temperature, self regulating cable automatically adjusts the power output depending on process temperature.

For example, during a startup or when ambient conditions are cold, the fluid in the pipe may require more heating power to maintain the desired process temperature. In this situation, the self regulating cable will produce a higher wattage per foot to heat the pipe. As the process media temperature increases, then need for that amount of input power decreases, and the self regulating cable automatically cuts the power output accordingly.

This video, courtesy of Raychem, provides a short but informative understanding of how self regulating heat tracing cable (sometimes referred to as "heat tape") works.

For more information, contact:
Instrument Specialties Inc.
3885 St. Johns Parkway
Sanford, FL 32771
phone 407.324.7800
fax 407.324.1104