Electric Machine Safety Control Circuit for High Voltage STO
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Solution Overview
Problem
Existing methods for controlling the safe-torque-off (STO) function in electric machines fail to reliably ensure safety at input voltages greater than or equal to 60 V while minimizing power losses and preventing undesired disconnection of the power supply.
Innovation Solution
A method and apparatus using a converter circuit with a transformer for electrically isolated energy transmission, a semiconductor switch, and an open-loop or closed-loop control system with a galvanically isolating element, such as an optocoupler, to generate a binary control signal and limit the output voltage, ensuring safe operation and low power losses across a broad input voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional voltage control method is used for STO function, then the safety function can be triggered, but power losses increase significantly at input voltages >= 60V
Solution Approach 1:
The patent introduces an intermediary voltage transformation stage between the input voltage (>=60V) and the STO control circuit. This intermediary converter circuit transforms the high input voltage to a suitable lower voltage level, enabling the STO function to operate reliably while avoiding the high power losses that would occur with direct voltage application.
Solution Approach 2:
The patent changes the voltage parameter through the converter circuit, transforming the input voltage >=60V into a transformed voltage suitable for STO operation. This parameter transformation allows the system to maintain safety function reliability while operating at high input voltages without excessive power losses.
2Loss of energy
If the input voltage is increased to >= 60V, then the power loss is reduced, but the control reliability of the safety function deteriorates
Solution Approach 1:
The converter circuit acts as an intermediary that enables the system to accept high input voltages (>=60V) while delivering a controlled, transformed voltage to the STO control circuit. This intermediary stage maintains control reliability by ensuring the STO circuit receives appropriate voltage levels regardless of the high input voltage.
Solution Approach 2:
The patent segments the voltage control function into two distinct stages: the input voltage acceptance stage (handling >=60V) and the STO control stage (receiving transformed voltage). This segmentation allows each stage to be optimized independently, maintaining control reliability while enabling high voltage operation with reduced power loss.
3Device complexity
If a simple voltage switching method is used, then the device complexity is low, but the ability to handle broad input voltage range deteriorates
Solution Approach 1:
The converter circuit is designed with multi-functionality, serving both as a voltage transformation device and as an adaptive interface for handling broad input voltage ranges (>=60V). This universal design allows the system to maintain relatively low complexity while gaining the ability to adapt to various high voltage inputs.
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
The solution effectively controls a broad input voltage range of up to 60 V with low power losses and ensures reliable safety functions, particularly the STO function, by using a redundant design and feedback loop for monitoring and adjusting the semiconductor switch operation.
Implementation Method 1
generating an electrically isolated output voltage for a normal operation of the frequency converter and for triggering the safety function from an input voltage, the output voltage is generated by a converter circuit
Implementation Method 2
an open-loop or closed-loop control system with a galvanically isolating element, such as an optocoupler
Data Source
AI summary
An apparatus and a method actuate a frequency converter of an electric machine having a safety function, in particular a safe-torque-off (STO) function. Wherein, by a preferably clocked converter circuit, an electrically isolated output voltage is generated from an input voltage, from which output voltage a control signal is generated for the frequency converter for the operation thereof in accordance with standards and for triggering the safety function. An actuation signal is generated for a semiconductor switch which is periodically connected to the input voltage, and the output voltage is limited when the output voltage exceeds a switching threshold.