The invention relates to a method for determining a fault in an electronically commutated electric motor, in which in every motor phase at least one stator coil of the electric motor is connected in parallel, with a motor phase being energized, and the current flowing through this motor phase being measured.
A method for checking the phases of an electronically commutated electric motor is known from DE 10 2011 083 217 A1. In this electric motor to be checked the respectively two coils arranged in each motor phase of the electric motor are connected serially. In order to reliably detect any phase interruption, successively at least two commutation steps of the electric motor are initiated, and a current measurement is performed in each commutation step. If here in one motor phase a power outage is detected, an interruption of the motor phase is concluded.
However, there are also electric motors in which the two coils are connected in parallel in the respective motor phase. Here, in case of a fault of such a coil connected in parallel a current flow still occurs. The electric motor still runs thereby, however with reduced capacity. If this defective electric motor is operated like a functioning one, severe consequential damages may arise in the electric motor.
The invention is therefore based on the objective of providing a method for the determination of a fault in an electronically commutated electric motor, in which in every motor phase two stator coils of the motor are connected in parallel, in which a defect in a motor phase is detected reliably, although the motor continues operating.
According to the invention the objective is attained such that the three motor phases are energized successively and during this electrification the current flowing is measured in the respective motor phase, with here the currents measured in the three motor phases being compared and any fault in the electric motor being detected when the currents measured differ from each other. The deviation of the currents may here be positive or negative, depending on the connection. However, it can always be reliably concluded that a motor phase, i.e. particularly one of the coils connected in parallel in the respective motor phase, is defective. By measuring the three motor phases directly one after the other, here any environmental influences can be eliminated and the relatively high differences in the currents can be detected directly.
Advantageously, in case of a deviation of a first current of the two currents, measured in the first motor phase, from the other two motor phases measured, a defect of a coil in the first motor phase can be concluded. In case of a defective coil in a parallel connection, relatively large differences occur in the currents. However, it must be distinguished between a delta connection and a star connection.
In one embodiment, in a delta connection of the three motor phases, the motor phase is detected as defective in which the current measured directly over the motor phase is lower than the current which is measured jointly over the two other motor phases connected serially. This is caused in that in a delta connection, the terminal resistance is calculated from the value of all three motor phases. This way, the terminal resistance changes in all current conditions.
In one alternative, in a star connection of the three motor phases, the motor phase is detected as non-defective in which the current measured is higher than the current measured separately in the two other motor phases. Here, the terminal resistance is equivalent to two phases connected serially, causing the current flowing through a phase with a defective coil, to behave differently than the current flowing through the two remaining phases with correctly operating coils.
In one variant the three motor phases have the same voltage applied for current measurements. This is particularly important because for the current measurement the same initial conditions must be given at the three motor phases of the electric motor, in order to allow comparing the currents measured.
In a further development the electric motor is switched to emergency operation after a fault has been detected. By such an emergency operation any further damage of the electric motor can be reliable prevented, for example overheating.
In one embodiment, a control device is used for the current measurement, which performs the check of the motor phases in a diagnostic mode. Advantageously it represents the same control device which is provided to control the electric motor. In the control device itself, here a measuring resistor is installed, which is used for the current measurement at the individual motor phases. This way, the suggested method represents a particularly cost-effective method to allow detecting defects in the electrically commutated electric motor.
The invention allows numerous embodiments, one of which shall be explained in greater detail using the figures shown in the drawing.
Shown are:
Identical features are marked with the same reference characters.
The hydrostatic actuator 1 is connected via a hydraulic line 7 to the slave cylinder 8, which moves a clutch 9. The adjustment of the position of the clutch 9 occurs based on the drive of the piston 3, arranged in a master cylinder, not shown in greater detail, by the electric motor 4 in the hydrostatic actuator 1.
During operation of the clutch 9 the electric motor 4 is addressed by a control device 5 in a commutation mode, with the electric motor 4 having three phases U; V; W.
The resistance of a defective phase Rphase,def amounts to
Rphase,def=Rsp
The resistance of the normal phase Rphase amounts to
Rphase=½Rsp.
At a current measurement, a terminal resistance Rtotal,1 acts, for example, between the terminals A and B amounting to
The terminal resistance Rtotal,2, which is yielded in a current measurement between the terminals A, C or B, C, amounts to
The current Iconductor,1 flowing between the terminals A and B, measured according to the ohmic resistance, amounts to
The current Iconductor,2, which is measured between the terminals A and B, but detected via the two motor phases V (terminal B and C) and W (terminal C and A), amounts to:
The deviation of the current Iconductor,1, which flows through the motor phase U, in which the defective coil 10 is located, amounts to
If the defective coil 10 is located directly between the terminals A, B subject to identical voltage, the resistance increases by the factor of 3/2; in the two other cases by a factor of 9/8. If now one by one the three phases are energized, when the defective coil 10 is located directly between the terminals A, B, the current is lower by ¼ than in the other two cases, in which the two other motor phases V, W are measured.
In a star connection as shown in
In a star connection it also applies that the resistance of the defective phase Rphase,def
Rphase,def=Rsp.
The resistance of the normal phase Rphase amounts to
Rphase=½Rsp.
The terminal resistance Rtotal between the terminal points B and C amounts here to
Rtotal=2*Rphase=Rsp.
The terminal resistance Rtotal, which is measured between the terminal points A, B and A, C, with one connection in parallel respectively comprising a defective coil 10, amounts to
Rtotal,2=Rphase=Rphase,def=3/2Rsp.
The current Iconductor,1, which is measured between the normal motor phase V and the terminal points B and C, amounts to
The current measured at the defective coil phases between the terminals A, B and A, C amounts to
Here, the deviation of the currents amounts to
With this method, even in electronically commutated electric motors showing two stator coils in each motor phase connected in parallel, it can be detected if the electric motor operates correctly.
Number | Date | Country | Kind |
---|---|---|---|
10 2013 215 192 | Aug 2013 | DE | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/DE2014/200370 | 8/1/2014 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2015/014362 | 2/5/2015 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
5057962 | Alley | Oct 1991 | A |
5574346 | Chavan | Nov 1996 | A |
6064172 | Kuznetsov | May 2000 | A |
7528611 | Kasztenny | May 2009 | B2 |
20070290690 | Nasswetter | Dec 2007 | A1 |
20090033357 | Lindsey | Feb 2009 | A1 |
20100060289 | Wiedenbrug | Mar 2010 | A1 |
20100091419 | Vedula | Apr 2010 | A1 |
20100327791 | Casey | Dec 2010 | A1 |
20110187304 | Anwar et al. | Aug 2011 | A1 |
20120032683 | Greif et al. | Feb 2012 | A1 |
20120074953 | Stickelmann | Mar 2012 | A1 |
20120212172 | Valdez | Aug 2012 | A1 |
20130041554 | Trunk | Feb 2013 | A1 |
20130245614 | Seebruch | Sep 2013 | A1 |
20130278282 | Leppich | Oct 2013 | A1 |
Number | Date | Country |
---|---|---|
102011083217 | Mar 2012 | DE |
2011012999 | Jan 2011 | JP |
2011083396 | Apr 2011 | JP |
2011009751 | Jan 2011 | WO |
Number | Date | Country | |
---|---|---|---|
20160178699 A1 | Jun 2016 | US |