This section is designed to serve as an introduction to the detailed product description pages. This brief discussion of some of the key specifications and features of Bertan power supplies should provide assistance in your evaluating the suitability of our products.
A supply that is voltage regulated maintains the output at a constant voltage over a specified range of load and environmental conditions. This is the most common form of regulation required by many high voltage applications. Power supplies that exhibit this type of regulation are referred to as constant voltage supplies. Typical voltage regulation for Bertan power supplies is from less than 0.001% (10 ppm) for precision electron beam and detector supplies to 0.1% for some high power units.
Current regulated supplies, as the name implies, maintain the output current constant. Current regulation is achieved in a similar way as voltage regulation. Most of the power supply circuitry is similar. Only the output sense element and feedback components are different.
The Bertan Series 105 has both constant voltage and constant current regulation. These units will automatically select regulation mode as a function of the control settings and load characteristics. This operation is called automatic crossover. Upon turn-on, the output voltage and current increase until the first parameter reaches its set value. Regulation then occurs for this parameter at this setting. The other non-regulated parameter, current or voltage, is at the value determined by the load characteristics and may vary. If it should increase (due to varying load conditions) to the value set by its control, the power supply will automatically switch regulation mode.
The two most common ways of specifying ripple are peak-to-peak and rms, each generally expressed as a percentage of the average dc output. Peak-to-peak, the more stringent method of characterizing a waveform, is measured by looking directly at the output and measuring the difference between the highest and lowest points. It is obviously always a greater number than the rms value
If the ripple waveform is a pure sinusoid, the peak-to-peak value is 2.8 times greater than the rms value. A purely sinusoidal ripple waveform is very rarely the case. If the waveform contains periodic spikes, then the measured peak-to-peak value can be 10, 100 or even more, times greater than the rms value. Without a detailed characterization of the ripple waveform there is no way of inferring what the peak-to-peak ripple is from an rms value.
In many applications voltage spikes will adversely affect the performance of the device being powered or introduce errors into associated instrumentation. In these situations knowledge of the maximum peak-to-peak high voltage variations is critical. Bertan specifies output ripple in peak-to-peak values, rather than rms, to more accurately express the true ripple component.
The simplest approach to implement is remote potentiometer programming. This is essentially a remotely located front panel control. In this mode, the potentiometer is connected between the power supply's reference output and common. The wiper of the potentiometer is then connected to the remote input. The applied programming voltage will be proportional to the potentiometer rotation. We recommend a 5k cermet or wirewound type control, although any type with a value between 1 kohm and 50 kohm will work. Resolution of the output setting is determined by the resolution of the potentiometer.
If, instead of continuous adjustment, a number of specific voltage values are required, then the potentiometer can be replaced by a series string of resistors and a multi-position switch. Resistors in series with a potentiometer can be used to achieve greater resolution over a limited voltage range than obtainable using only a potentiometer. One can use a precision low temperature coefficient resistors with a total resistance of approximately 5 kohm. RN55E metal film resistors will work well in this application.
Remote voltage programming is accomplished by applying a signal voltage at the control input. The programming voltage range required by most Bertan power supplies is typically 0 to +5V, although some models require 0 to -5V or 0 to +9V. If your programming source produces a higher voltage, such as 0 to +10V, a voltage divider can be used to reduce the voltage applied to the power supply's program input. Resolution of remote analog voltage programming is essentially infinite.
Power supply input impedance is typically high, 1 megohm or greater. For best accuracy and lowest noise, the circuit providing the programming signal should have a low output impedance.
A programming source output impedance of 100 ohms, for example, results in an error of less than 0.01%. The error caused by the programming source impedance can be easily predicted.
Digital programming of any Bertan power supply that includes remote analog programming capability can be accomplished using an external digital to analog converter (DAC). The DAC output would be applied to the power supply programming input.
The voltage monitor circuit relies on a precision high voltage resistive divider to determine the exact output voltage. It is this signal, after suitable buffering, that appears at the voltage monitor output. The current monitor circuit is also ground referenced and precisely measures output current without injecting a voltage drop or any other error at the power supply output. This circuit does not interfere with the power supply output return, which remains at ground.
The output monitor signals are compatible with analog meters, digital meters and external instrumentation circuits. Most units have an output voltage range of 0 to +5V corresponding to zero to maximum rated output (either voltage or current), and an output impedance of 10kohm. This output impedance provides isolation between the power supply and the external circuit. There is no effect on the power supply operation even if the remote monitor pin were to be shorted to ground.
When using a voltmeter to read the monitor output, the input impedance of the voltmeter will affect the measurement accuracy. For best accuracy, the circuit measuring the monitor signal should have a high input impedance. For an input impedance of 10 megohm the resulting error would be 0.1%.
Remote digital monitoring can be implemented using an analog to digital converter (ADC). Call Del Application Engineering for assistance if required.
Bertan manufactures high voltage cable assemblies and can provide a wide range of standard and custom cables to meet your requirements. See the product information on the HV Connectors and Cable page or call Bertan application engineering for additional assistance.
Encapsulation of the high voltage components is employed in all Bertan power supplies. This provides significantly improved performance and reliability. Encapsulation provides a clean, stable, well-defined long life environment for all critical high voltage components. It prevents the initiation of corona and other destructive phenomena which can occur in air at high voltage potentials. Encapsulation is performed on Bertan product using custom designed automatic dispensing equipment and special vacuum chambers. The materials used are selected for their mechanical and thermal properties as well as their insulating characteristics.
Voltage regulated power supplies must be protected against short circuits by providing safe, well defined current limiting. Open circuit protection may initially seem to be a trivial requirement. However, for current regulated supplies, an open circuit is analogous to a short circuit on a voltage regulated supply. Current regulated power supplies are protected against open circuits by providing safe, well defined voltage limiting.
For remotely programmed supplies, the output can also be shut off by setting to program voltage to zero. Another way of accomplishing this function is with an interlock switch to shut down the primary 115Vac, 28Vdc or +15Vdc input power. The installation and operating manual will provide application information on this feature.
The following product information sheets provide in depth information on each Bertan standard catalog high voltage product. For additional information or assistance with your high voltage application, contact Bertan Application Engineering.
