Coffee Machine Motor Ramp Control to Reduce Noise and Current Peaks
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Solution Overview
Problem
Fully automatic coffee machines with electric motors for grinders experience noise pollution and electromagnetic compatibility (EMC) issues due to sudden voltage application, leading to reduced motor lifespan and inefficient grinding processes.
Innovation Solution
The method involves using a ramp function to modulate the drive power of the electric motor, gradually increasing or decreasing the rotational speed over at least 200 ms to prevent sudden current peaks, thereby reducing noise and improving EMC, by applying voltage pulses with a specific duty cycle or phase modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If full available voltage is applied to the electric motor for start-up, then the motor reaches target speed quickly (high productivity), but noise development increases and current peaks occur (harmful factors)
Solution Approach 1:
The patent applies periodic voltage pulses with varying duty cycles to the motor during start-up and operation. Instead of continuous full voltage, the control device delivers pulsed voltage where the duty cycle is dynamically adjusted according to a ramp function, creating periodic action that limits current peaks while maintaining adequate motor performance
Solution Approach 2:
The patent dynamically changes the duty cycle parameter of the voltage pulses over time using a ramp function. The duty cycle increases gradually from a lower initial value to a higher operational value, which controls the average voltage applied to the motor and thereby limits current peaks and noise while still achieving the required rotational speed
2Speed
If full available voltage is applied to the electric motor, then the motor responds quickly, but the serviceable life of the motor is reduced
Solution Approach 1:
The motor is driven with periodic voltage pulses rather than continuous full voltage, which reduces thermal and mechanical stress on motor components. The pulsed operation with controlled duty cycle extends motor life by preventing excessive heating and reducing wear on bearings and windings
Solution Approach 2:
The patent applies a preliminary low duty cycle during motor start-up before increasing to full operational duty cycle. This preliminary gentle start-up phase prevents sudden current shocks and mechanical stress on the motor, thereby extending serviceable life while still achieving the required speed
3Productivity
If the drive power is increased rapidly to reach target rotational speed, then grinding efficiency is high, but electromagnetic compatibility is compromised
Solution Approach 1:
The duty cycle parameter is changed gradually according to a ramp function rather than abruptly. This controlled parameter transition limits the rate of change of current and voltage, thereby reducing electromagnetic interference and improving EMC while still achieving the required grinding speed
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for a quiet and efficient grinding process with extended motor lifespan by reducing noise and current peaks, ensuring the motor reaches the required speed without compromising grinding efficiency.
Implementation Method 1
an electric motor (E), in particular the motor of a grinder (2a) of a fully automatic coffee machine (1)
Implementation Method 2
a drive power (P) that is provided to the electric motor (E) is modulated by using a ramp function... driven using a periodic modulation having a certain duty cycle that is based on the ramp function
Data Source
AI summary
A method for actuating an electric motor includes modulating a drive power provided to the electric motor by using a ramp function for a change in rotational speed of the electric motor from a starting rotational speed to a target rotational speed. The target rotational speed is only reached after at least 200 ms, starting from the starting rotational speed. An apparatus, a fully automatic coffee machine having the apparatus, a computer program product and a computer-readable storage medium are also provided.