摘要:
The coil temperature of an electric motor is estimated from the balance of heat in relation with the surrounding components. In particular, the amount of heat generated in the motor coil is proportional to the square of the electric current conducted through the motor coil. The electric current may be either measured directly by using a current sensor or computed from the voltage applied to the motor coil and the rotational speed of the motor. Because the heat transfer from the motor coil to the surrounding component parts is accounted for as well as the amount of heat generated in the motor coil, the motor coil temperature can be estimated accurately. The surrounding components may comprise a motor shaft, a commutator, a rotor core that may include a permanent magnet, a yoke rotatably supporting an end of the motor shaft and a combination thereof. The heat balance of the adjacent member is also accounted for. Thereby, the operation of the electric motor under an overload condition can be prohibited when required, and can be restored as soon as the overload condition is resolved so that the user can obtain the benefit of the use of the electric motor as much as possible without running the risk of causing damage to the electric motor.
摘要:
A load circuit disconnection detector includes: a current sensor (16) for detecting current flowing through a wire (W1) of a load circuit; and a protective device (100) for estimating temperature of the wire (W1) based on the detected current and forcibly turning off a semiconductor switch (Q1) if the estimated temperature of the wire reaches threshold temperature. The load circuit disconnection detector determines that there is a connection failure in the load circuit if a temperature increase calculated by a temperature calculation unit (24) is zero even a predetermined time (P1) after the semiconductor switch (Q1) is turned on.
摘要:
The invention relates to a device (1) for protecting a load (2), with a first current path (100) having two lines (101, 102), and a monitoring arrangement for detecting an imminent overload of the electrical load (2). In order to enable the detection of an imminent overload on a load (2), it is proposed that the monitoring arrangement comprises a first temperature measuring unit (18), an evaluation unit (4) and a first transducer (10), which establishes an electrically conductive connection between the two lines (101, 102) of the first current path (100), wherein the first temperature measuring unit (18) is electrically isolated from the first transducer (10) and can record a temperature of the first transducer (10), wherein the evaluation unit (4) can determine, using recorded temperatures of the first transducer (10), a temporary heating behaviour of the first transducer (10), and can determine, by evaluating the determined temporary heating behaviour of the first transducer (10), an imminent overload on the load (2).
摘要:
A digital thermal model for compensating for error in a current transformer used in a solid-state overload relay. The thermal model implements a difference equation that determines using a low-pass filter two parameters corresponding to calibration points along an overload trip curve. The trip curve is adjusted at an ultimate trip current (one calibration point) independently of a trip time at a locked rotor current (another calibration point) of a motor protected by the overload relay. The ultimate trip current and trip time can be adjusted based on a motor full load current set by a user. Large CT error will cause the thermal model to adjust the trip time at the locked rotor current, increasing the range of acceptable CT error, allowing the overload relay to have a wider adjustment range.
摘要:
Die thermische Überwachung eines Umrichters für einen Elektromotor eines Fahrzeugs soll verbessert werden. Daher wird ein Verfahren vorgeschlagen, bei dem die Temperatur des Umrichters gemessen wird. Außerdem wird die abgegebene Leistung des Umrichters ermittelt. Mit Hilfe eines thermischen Modells des Umrichters mit der abgegebenen Leistung als Eingangsgröße wird die Temperatur des Umrichters geschätzt. Die geschätzte Temperatur wird mit der gemessenen Temperatur verglichen und es wird ein entsprechendes Überwachungssignal bereitgestellt. Damit kann bereits im Teillastbereich eine Abweichung der gemessenen Temperatur von der berechneten Temperatur und damit ein entsprechender Fehler im Kühlsystem erkannt werden.
摘要:
Ensemble de protection thermique (1) comprenant une unité de contrôle (10) reliée par des moyens de communication 11 à un bloc de protection (20) déporté comprenant : des moyens de mesure (21) du courant (I) ; des premiers moyens intégrateur (22) calculant une première valeur d'intégration (Va) correspondant à l'intégration en continu du courant (I) pendant une première durée d'intégration (t1),
L'unité de contrôle (10) comporte des seconds moyens intégrateurs (12) calculant une seconde valeur d'intégration (Vb) pendant une seconde durée d'intégration (t2), ladite seconde valeur correspondant à l'intégration des premières valeurs d'intégration (Va) communiquées à l'unité de contrôle (10) après chaque première durée d'intégration (t1). Des moyens de calcul (15) déterminent un état de fonctionnement thermique de la charge (30) à partir d'une comparaison entre la seconde valeur d'intégration (Vb) et un seuil de température maximale fixée (S max ).
摘要:
A protection apparatus for a load circuit is provided which can miniaturize electric wires and semiconductor switches by using a switch circuit simulating the current · interruption time characteristics of fuses. A conductor resistance r and a heat resistance R used in each of a heat generation temperature calculation expression and a heat dissipation temperature calculation expression are respectively changed into a pseudo conductor resistance r* and a pseudo heat resistance R*, then the heat generation amount and the heat dissipation amount of the electric wire are calculated, and current temperature of the electric wire is estimated. When the estimation temperature reaches allowable temperature, an electronic switch S1 is turned off to thereby protect the load circuit. As a result, each of the electric wires and the semiconductor switches used in the load circuit can be protected from over heat.