Ripple Voltage
Ripple Voltage is the difference in voltage between “peak” and “valley” from our DC power supply.
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Large amounts of current flowing back into the power supply can cause voltage spikes at the output terminals of the motor systems as well as on the power supply. The excess current can be produced by the motor acting as a generator or by the stored energy on the motor flowing back to the supply during fast decay. This occurs because the kinetic energy that the motor possesses when it is spinning has to dissipate - which occurs by energy being transferred back into the circuit. This voltage that is output will cause noise to the input. The goal is to minimize the voltage spikes by controlling and absorbing all of the excess energy.
Ripple Current
When driving the motor, the H-bridge alternates between drawing current to the different coils of the BLDC motor. This causes the current to fluctuate, thus causing a current ripple.
When driving the motor, the H-bridge alternates between drawing current from the power source and DC link capacitor, and cycling the current through the motor. This causes a current ripple.
Structure of a capacitor
A capacitor is a device that can store electrical energy. Taken simply, a capacitor consists of two conductive plates separated by an insulating material called the dielectric. The main structure is shown here:
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Ceramic capacitors are smaller in size and usually have a capacity of up to 1 uF; they do not care which of the pins is connected to the plus terminal and which to the minus.
Input Capacitor Selection
A bulk capacitor can ensure that the supply voltage and/or motor voltage does not drop too much incase of current spikes/surges.
We need to know what the inrush current/surge current is. Once we know the voltage drop we need, the capacitor size can be calculated by the formula:
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