JPH0310054B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an electric dynamometer that is directly connected to a machine under test such as an engine to measure the output torque of the machine under test. The present invention relates to a torque measurement method for a DC electric dynamometer that measures rotational speed and the like and calculates torque by calculation.

In general, this type of DC electric dynamometer (hereinafter referred to as a dynamometer) includes armature hysteresis loss and eddy current loss, brush friction loss, bearing friction loss, rotor windage loss, stray load loss, armature There is copper loss in the circuit windings, and for this reason, the torque calculated only from the measured armature terminal voltage, armature current, and rotational speed cannot be said to be accurate. Therefore, conventionally, the torque is calculated using the following equation that takes into account the losses described above. In other words, the torque value T considering the loss
is, T=K・V _a・I _a ±I ² / _a・R _a ±I _a・e _b ±K _H・Φ ²・N±K _E
・Φ ²・N ² ±K _b・N±K _B・N ^1.5 /N* *±K _W・N ² ±K _S・I ² / _a・N/ ......(1) It can be expressed as follows.

Where, K is the torque constant, V _a is the armature terminal voltage, I _a is the armature current, N is the rotation speed, R _a is the resistance of the armature circuit, e _b is the brush contact voltage drop, and K _H is the hysteresis loss. Φ is the magnetic flux of the main pole, K _E is the eddy current loss constant, K _b is the brush friction loss constant, K _B is the bearing friction loss constant, K _W is the windage constant, K _S is the stray load is the loss constant. Also, the (+) sign in equation (1) represents the case where the dynamometer absorbs the load from the machine under test, and the (-) sign represents the case where the dynamometer absorbs the load from the machine under test.
The symbol indicates the case where the dynamometer drives the machine under test.

By the way, such a DC electric dynamometer does not always absorb or drive a constant load, but in order to absorb or drive a variety of loads,
If the torque is calculated using the above-mentioned formula, a measurement error may occur in some cases. That is, since the current flowing through the armature circuit changes due to changes in absorption or driving load, the temperature of the armature circuit winding itself changes accordingly, and the resistance value of the armature circuit winding changes. However, since the armature winding in the armature circuit is rotating and the resistance value cannot be measured during rotation, conventional measurement methods generally measure the resistance of the armature winding when it is stationary and the stator side armature circuit. The resistances of the compensation winding and the commutator winding are measured and summed, and the measured value (R _a ) can be used to calculate the copper loss in the armature circuit [(I _a ²・R _a ) shown in equation (1)]. I am trying to calculate it. For this reason, an error occurs between the actual copper loss and this appears as a measurement error when torque is calculated, resulting in a drawback that accurate torque measurement may not be performed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a torque measuring method for a DC electric dynamometer in which measurement errors due to changes in resistance values of armature circuit windings are reduced.

The torque measuring method of the DC electric dynamometer of the present invention includes:
Detect the voltage drop in the armature circuit on the stator side of the DC electric dynamometer, multiply this voltage drop by a constant to find the total voltage drop in the armature circuit, and calculate the armature terminal voltage, armature current, rotation speed, and armature This method is characterized by calculating the torque of the device under test from the total voltage drop and loss of the circuit.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but before that, the basic idea of this measurement method will be described. In the case of a separately excited DC generator, the armature circuit usually consists of an armature wire, a compensation winding, and a commutator winding. Now, the resistance values of each winding are r _a (armature winding resistance), r _c , (compensation winding resistance), r _I
(commuting pole winding resistance), the armature circuit resistance R _a
becomes R _a = r _a + r _c + r _I. Therefore, when the armature circuit current I _a flows, the armature circuit voltage drop is I _a
×R _a =I _a ×( _ra + r _c + r _I ). Here, the voltage drop I _a × _ra in the armature winding cannot be easily detected because the armature is a rotating body.

However, the voltage drop between the compensation winding and the interpolation winding I _a ×
(r _c +r _I ) can be easily detected because it is the stator winding. On the other hand, armature winding resistance r _a , compensation winding resistance r _c ,
Each of the commutating pole winding resistances r _I has a constant value, and if the following resistance ratio K _R is assumed, this K _R becomes a constant value.

K _R = (r _a + r _c + r _I ) / (r _c + r _I ) = R _a / (r _c + r _I ) Therefore, the armature circuit resistance R _a is R _a = K _R × (r _c
+r _I ). Further, the voltage drop in the armature circuit is I _a ×R _a =K _R ×(r _c +r _I ) × I _a . Here, (r _c
As stated above, +r _I )×I _a is the voltage drop across the compensation winding and the commutator winding of the stator side armature circuit, which is easy to detect. Therefore, if the armature winding resistance r _a , compensation winding resistance r _c , and commutator winding resistance r _I are measured in advance when the armature is stationary and the resistance ratio K _R is determined, the armature circuit voltage during rotation can be determined. The drop is obtained by multiplying the detected voltage drop (r _c +r _I )×I _a of the compensation winding and the interpolation winding by the resistance ratio K _R .

In addition, since the armature winding, compensation winding, and commutator winding are connected in series, the same armature current flows and the temperature change of the resistance due to the current change is considered to be the same, so there is no practical problem. None. Therefore, the armature circuit voltage drop obtained by multiplying the detected voltage drop of the compensation winding and the commutator winding, that is, the voltage drop of the stator side armature circuit by the resistance ratio K _R , is I _a ×R _a = K _R × (r _c + r _I ) ×
I _a ² × _{R a =} K _R × ( _{r c}
+r _I )×I _a ² is the copper loss, substituted into (1), and the torque T
By calculating , it is possible to accurately grasp changes in copper loss due to temperature changes in armature circuit resistance due to changes in absorption or drive load amount, and it is possible to improve torque measurement accuracy. FIG. 2 is a block diagram showing an embodiment. In the figure, 1 is the armature of the electric dynamometer, E is the internal induced voltage, r _a is the armature winding resistance, r _I is the interpolation winding resistance, r _c is the compensation winding resistance, and 2 is the compensation winding resistance. A device for deriving the voltage drop I _a × (r _c ⁸ + r _I ) of the commutator winding, 3 a device deriving the armature current I _a , 4 a voltage drop I _a × of the compensation winding and the commutator winding (r _c + r _I ) is the ratio of the armature circuit resistance R _a = r _a + r _c + r _I to the resistance of the compensation winding and the commutator winding r _c + r _I K _R = R _a / (r _c + r _I ) 5 is a circuit that calculates the armature circuit voltage drop by multiplying the armature circuit voltage drop K _R × I _a (r _c + r _I ), 6 is a circuit that calculates the copper loss by multiplying the armature current I _a ( 1) Copper loss (I _a ²・
This is a torque calculation device that calculates torque using the copper loss K _R ×I _a (r _c +r _I ) obtained by the circuit 5 that calculates the copper loss instead of R _a ).

Although the above embodiment shows the case where there is a compensation winding and a commutator winding, it goes without saying that the copper loss of the armature circuit can be found in the same way even if there is only one commutator winding. .

As described above, the present invention detects the voltage drop in the stator side armature circuit, and calculates the ratio of the armature circuit resistance at rest to the resistance of the stator side armature circuit to determine the voltage of the stator side armature circuit. Since the total voltage drop in the armature circuit is calculated by multiplying the voltage by the voltage drop, the copper loss is calculated, and the torque is calculated. Therefore, it is possible to accurately grasp the change in copper loss due to temperature changes in the armature circuit resistance. It has the excellent effect of allowing extremely accurate torque measurements.

[Brief explanation of the drawing]

The drawing is a block diagram showing an embodiment of the method for measuring torque using a DC electric dynamometer according to the present invention. 1... Armature of electric dynamometer, 2... Device for deriving voltage drop of compensation winding and commutator winding, 3... Device for deriving armature current, 4... Calculating armature circuit voltage drop 5...Circuit for calculating copper loss,
6...Torque calculation circuit.

Claims (1)

[Scope of Claims] 1. In a DC electric dynamometer that is directly connected to a machine under test to measure the torque of the machine under test, detecting a voltage drop in a stator side armature circuit of the DC electric dynamometer,
Multiply this voltage drop by a constant to find the total voltage drop in the armature circuit, and calculate the torque of the machine under test from the armature terminal voltage, armature current, rotation speed, and total voltage drop and loss in the armature circuit. A method for measuring torque using a DC electric dynamometer. 2. The method for measuring torque in a DC electric dynamometer according to claim 1, wherein the DC electric dynamometer has a commutator winding and a compensation winding. 3. The method for measuring torque in a DC electric dynamometer according to claim 1, wherein the DC electric dynamometer has only a commutator winding.