Electric Drive Brake Sequencing to Cut Motor Start Heat
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Solution Overview
Problem
Existing electric drive devices experience unnecessary thermal losses and inefficiencies due to the simultaneous activation of the motor and brake, which leads to increased heating and the need for motor over-dimensioning to compensate for these losses.
Innovation Solution
A method and control unit that independently switch the phase conductors to minimize thermal losses by activating the brake before the motor, using a defined waiting period to ensure the brake is open before the motor is fully powered, thereby reducing the period of locked operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the brake and motor are activated simultaneously by applying voltage to all phase conductors, then the motor can begin operation, but high thermal losses occur in the motor during the brake opening period causing unnecessary heating
Solution Approach 1:
The phase conductors are divided into two groups: a first subset connected to the brake and a second subset connected to the motor. By independently controlling the switching of these subsets, the patent segments the power supply process to activate the brake first (using only the first subset), then activate the motor afterward (using both subsets), thereby eliminating thermal losses during brake opening.
Solution Approach 2:
The brake is activated in advance by switching on only the first subset of phase conductors before the motor is activated. This preliminary action ensures the brake is already opening or fully open before the motor receives full power, preventing the motor from operating under mechanical constraint and avoiding thermal losses.
2Reliability
If the motor is over-dimensioned to compensate for the increased load at start due to the brake, then the required performance is achieved, but the motor size and cost increase
Solution Approach 1:
By activating the brake before the motor using only the first subset of phase conductors, the motor is ensured to be free of mechanical constraint before full power is applied. This eliminates the need for over-dimensioning, allowing the motor to be sized exactly for the required application performance.
3Loss of energy
If the brake is connected to only a subset of phase conductors and activated first with a waiting period, then thermal losses are reduced, but the control complexity increases
Solution Approach 1:
The control system manages two separate switching operations for two subsets of phase conductors. The first subset switches the brake on/off, and the second subset switches the motor on/off. This segmented control approach systematically manages the additional complexity while achieving the energy loss reduction.
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
Significantly reduces thermal load on the motor windings, increases motor availability, and allows for more starts per unit time or longer continuous operation with reduced cooling-down pauses.
Implementation Method 1
By applying the brake operating voltage, an electromagnet 604 of the brake 60 is activated, with the result that the friction disc 602 is pulled away from the friction surface 603
Implementation Method 2
an axially movable friction disc 602 of the brake 60 is pressed by a pressure spring against a friction surface 603 that is connected to the motor in a rotationally fixed manner, with the result that the motor is braked or held securely
Implementation Method 3
an axially movable friction disc 602 of the brake 60 is pressed by a pressure spring against a friction surface 603
Data Source
AI summary
A method operates an electric drive device having a voltage supply with phase conductors providing multiphase supply voltage, a multiphase electric motor connected to the phase conductors, an electrically actuatable brake acting on the motor and switching between a position blocking the motor in a voltage-free state and an open position releasing the motor in a voltage-supplied state, the brake being solely connected to a subset of the phase conductors, the brake requiring a defined opening period until reaching the open position after switching from voltage-free to voltage-supplied states, and switches independently interrupting the phase conductors. In a starting state, the phase conductors are interrupted. Based on the starting state, only the subset of phase conductors connected to the brake are switched to conduct a current, and after a defined waiting period, the motor is activated by switching remaining phase conductors to conduct a current.