Joachim Posted October 20, 2011 Share Posted October 20, 2011 Hello, Is it possible to run linear motors (u shape) or torque motors which do have only 2 phases? I'm used to work with the Geobrick-lv which is able to run 2 phase motors ( 2phase steppers working fine also 3 phase motors) so it should be a mix of the 2 modes ( stepper and 3 phase brushless) Any idea or tipp? Thanks and Best regards Joachim Link to comment Share on other sites More sharing options...
curtwilson Posted October 21, 2011 Share Posted October 21, 2011 The Geo Brick LV has 4 half bridges per motor in its power stage, which can be organized as 2 full (H) bridges for 2-phase motors with electrically independent phases. Alternately, you can use 3 of the half bridges for 3-phase motors that are Y or Delta wound. Most servo amplifiers (such as our higher voltage Geo Brick) have only 3 half bridges per motor, so you cannot drive 2-phase motors while keeping the phases independent. However, it is possible to run them with the phases connected. You can connect one phase between the U and V phase outputs, and the other phase between the V and W phase outputs. This has been done successfully with, for example, the Swiss Etel 2-phase brushless servo motors. The disadvantage of this technique is that your effective bus voltage is reduced by 30% compared to independent phases. (You can use only 1/sqrt(2) of the supply voltage.) In PMAC, the issues of 2-phase versus 3-phase motors and stepper versus servo motors are independent questions. The number of phases is dealt with by the power-stage wiring and the value of Ixx72 (1/4 or 1/3 of a cycle). The issue of stepper versus servo (really open-loop versus closed loop control) is dealt with by selecting simulated versus real feedback. However, the vast majority of stepper motors are 2-phase, and the vast majority of servo motors are 3-phase, so these issues sometimes get confused. Link to comment Share on other sites More sharing options...
Joachim Posted October 21, 2011 Author Share Posted October 21, 2011 The Geo Brick LV has 4 half bridges per motor in its power stage, which can be organized as 2 full (H) bridges for 2-phase motors with electrically independent phases. Alternately, you can use 3 of the half bridges for 3-phase motors that are Y or Delta wound. Most servo amplifiers (such as our higher voltage Geo Brick) have only 3 half bridges per motor, so you cannot drive 2-phase motors while keeping the phases independent. However, it is possible to run them with the phases connected. You can connect one phase between the U and V phase outputs, and the other phase between the V and W phase outputs. This has been done successfully with, for example, the Swiss Etel 2-phase brushless servo motors. The disadvantage of this technique is that your effective bus voltage is reduced by 30% compared to independent phases. (You can use only 1/sqrt(2) of the supply voltage.) In PMAC, the issues of 2-phase versus 3-phase motors and stepper versus servo motors are independent questions. The number of phases is dealt with by the power-stage wiring and the value of Ixx72 (1/4 or 1/3 of a cycle). The issue of stepper versus servo (really open-loop versus closed loop control) is dealt with by selecting simulated versus real feedback. However, the vast majority of stepper motors are 2-phase, and the vast majority of servo motors are 3-phase, so these issues sometimes get confused. Thanks, So if i understand right, it' s a Yes. I can configure the geobrick-lv as i' m used to do with a 3phase motor, just change ixx72. Great if it works, we see great potential selling the geobrick with our airbearing rotary stage Best regards Joachim Link to comment Share on other sites More sharing options...
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