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| university:courses:alm1k:circuits1:alm-ac-sync-motors [22 Apr 2022 20:11] – [Calculating Run/Start capacitor Value:] Doug Mercer | university:courses:alm1k:circuits1:alm-ac-sync-motors [23 Apr 2022 16:23] (current) – [Calculating Run/Start capacitor Value:] Doug Mercer | ||
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| **Stepper Motor Specifications** | **Stepper Motor Specifications** | ||
| - | For this example setup a MITSUMI M35SP-7 stepping | + | For this example setup a MITSUMI M35SP-7 stepping |
| * Working Voltage: DC 5.4~6.6V | * Working Voltage: DC 5.4~6.6V | ||
| Line 135: | Line 135: | ||
| Referring back to figure 1 we see that voltage across the Run capacitor is the Coil A voltage minus the Coil B voltage. Using the RMS values from figure 5 we have the coil B current is 64.26 mA RMS and the VA-VB voltage is 2.3 V RMS. | Referring back to figure 1 we see that voltage across the Run capacitor is the Coil A voltage minus the Coil B voltage. Using the RMS values from figure 5 we have the coil B current is 64.26 mA RMS and the VA-VB voltage is 2.3 V RMS. | ||
| - | This gives us the capacitive reactance, which, multiplied by the amperage and then divided by the voltage, | + | This gives us the capacitive reactance, which, multiplied by the amperage and then divided by the voltage, |
| Now that we have an approximate value for the Run Capacitor we can drive the motor with just one of the SMU channels or with both channels set to the same phase as shown in figure 6. To make a 74 uF capacitor, a close approximation is to use a 47 uF cap in parallel with a 33 uF cap for a total of 80 uF. Another close approximation would be a 47 uF cap in parallel with 22 uF or 69 uF. Generally caps of these values will be polarized electrolytic capacitors. Using such capacitors on AC signals without a DC bias is not a good idea long term but in this use case as a lab experiment they will work fine. Just choose capacitors with much higher voltage ratings such as 35 V or higher. | Now that we have an approximate value for the Run Capacitor we can drive the motor with just one of the SMU channels or with both channels set to the same phase as shown in figure 6. To make a 74 uF capacitor, a close approximation is to use a 47 uF cap in parallel with a 33 uF cap for a total of 80 uF. Another close approximation would be a 47 uF cap in parallel with 22 uF or 69 uF. Generally caps of these values will be polarized electrolytic capacitors. Using such capacitors on AC signals without a DC bias is not a good idea long term but in this use case as a lab experiment they will work fine. Just choose capacitors with much higher voltage ratings such as 35 V or higher. | ||
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| * Rated Current/ | * Rated Current/ | ||
| * Coil DC Resistance 95 Ω/phase | * Coil DC Resistance 95 Ω/phase | ||
| - | * Phase Inductance: | + | * Phase Inductance: |
| Stepper motors specified for 12 Volt or higher operation cannot be driven directly from the M1k SMU channels. An AC to AC step-down transformer can be used as shown in figure 9 to provide a suitable 60 Hz voltage level to drive the motor. | Stepper motors specified for 12 Volt or higher operation cannot be driven directly from the M1k SMU channels. An AC to AC step-down transformer can be used as shown in figure 9 to provide a suitable 60 Hz voltage level to drive the motor. | ||
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| To measure the coil voltages, which will be greater than the 0 to 5 V input range of the M1k, 11:1 voltage dividers are used between the coils and the Split I/O inputs of M1k. The resistor divider values shown are just suggested values and just about any combination of resistors that provides enough reduction in the voltage to fit within the M1k input range is possible. Refer to this tutorial on how to calibrate external voltage dividers: [[university: | To measure the coil voltages, which will be greater than the 0 to 5 V input range of the M1k, 11:1 voltage dividers are used between the coils and the Split I/O inputs of M1k. The resistor divider values shown are just suggested values and just about any combination of resistors that provides enough reduction in the voltage to fit within the M1k input range is possible. Refer to this tutorial on how to calibrate external voltage dividers: [[university: | ||
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| + | =====Appendix: | ||
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| + | These lowest cost " | ||
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| + | {{ : | ||
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| + | <WRAP centeralign> | ||
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| + | They can have either 16:1 or 64:1 gear reduction so the output shaft will rotate very slowly when driven by moderate frequency sine sources like 60 Hz. | ||
| + | |||
| + | {{ : | ||
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| + | <WRAP centeralign> | ||
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| + | The gear reduction should not change the voltage and current waveforms so these motors could be used to demonstrate these same properties of AC induction motors. | ||
| **For Further Reading:** | **For Further Reading:** | ||
university/courses/alm1k/circuits1/alm-ac-sync-motors.txt · Last modified: 23 Apr 2022 16:23 by Doug Mercer