Bachmann PVA20x (Proportional Valve Amplifier)
As hydraulic systems become more sophisticated, the need for electronic control of hydraulic components is increasing. In order to reduce amplifier size and power waste, PWM has become the standard for all valve amplifiers. The Bachmann PVA200 series offer state of the art PWM output modules. This integrated solution is of great benefit to our customers in maximising the performance and minimising commissioning and service costs.
Taking Full Control
PWM allows the use of electronics for current regulation; varying the length of the pulse, the valve can take any position as required for letting through the necessary amount of oil. Known problems, when using PWM, are stiction and hysteresis. A solution for this problem is dither. Dither is a rapid, small movement of the spool around the desired position. It is intended to keep the spool moving to avoid stiction and average-out hysteresis. The PVA200 modules generate dither separately from the PWM frequency and then superimpose it on top of the output current. This allows the user to independently control the current level, as well as the dither frequency and amplitude. The dither will therefore be constant for any current level, its frequency and amplitude.
The PVA200 modules are designed to control directly, without extra amplifiers, one coil, bipolar coils or dual coils. With the PVA208 up to eight coils can be controlled on just 55mm width. The current regulated control compensates automatically the changing coil characteristics caused by temperature changes. Each coil can be controlled by its own configurable curve using up to 20 points.