CN102437547A - Brake unit overload method - Google Patents

Abstract

The invention discloses a brake unit overload method which comprises the following steps: in a discharge process, utilizing instantaneous overload capability of a brake resistor to consume power in a circuit with a brake unit so as to achieve a discharge effect; in order to guarantee that the brake resistor is not burned out in the discharge process, by utilizing a parameter provided by a manufacturer of the brake resistor, fitting a characteristic curve of overload multiple and overload time of the brake resistor; if resistor operation condition exceeds the characteristic curve, alarming that the brake unit is overloaded. According to the method in the invention, protection of the brake resistor can be improved.

Description

Brake unit is crossed support method

Technical field

The present invention relates to three-phase electricity overvoltage protection field, relate in particular to the method that motor, Switching Power Supply etc. are used the overvoltage protection of three phase supply equipment.

Background technology

The three-phase mains supply power mode is used very extensive in motor, Switching Power Supply etc.Because motor can produce very big braking energy in the fast braking process, these energy can turn back on the dc bus with the mode of electric energy, make DC bus-bar voltage moment raising.If protection can not burn out the element in the circuit in addition.

Current protection busbar voltage promotes topmost method suddenly and on dc bus, adds brake unit exactly.When brake unit detects busbar voltage above a limit value, begin bus discharge.Because during the brake unit discharge, all on brake resistance, consume energy unnecessary on the dc bus with the mode of heat energy.This just might cause a problem, and when the energy that consumes on the resistance surpassed the overload capacity of brake resistance, brake resistance can be burnt out.This just need protect to brake resistance on brake unit.

All frequency converters all have i on the market at present ²The overload protection of t form, but the overload protection in the brake unit is but very simple.Exactly when brake unit be 1 discharge when surpassing 10S with duty ratio, just report the brake unit overload.This protection can not be protected brake resistance completely.Through experimental verification; If in the discharge process; The copped wave duty ratio of brake unit is always less than 1, but brake resistance is in overload always, if when this time surpasses the overload time of brake resistance under this operating mode; Brake resistance will be burnt out, but brake unit can not reported overload in this case.

Summary of the invention

Technical problem to be solved by this invention is: provide a kind of brake unit to cross support method, this method is mainly used in the protection brake resistance, burns out because of overheated to prevent brake resistance.

The technical scheme that the present invention solves its technical problem employing is: brake unit utilizes the momentary overload capacity of brake resistance to consume the power in the circuit in discharge process, reaches discharge effect; In order to guarantee that brake resistance is not burnt out in discharge process, the parameter of utilizing the producer of brake resistance to provide, the overload magnification of a brake resistance of match and the characteristic curve of overload time; If the resistance operating condition exceeds this characteristic curve, then report the brake unit overload.

It specifically is to adopt the method that may further comprise the steps that above-mentioned brake unit provided by the invention is crossed support method:

(1) overload time that provides according to resistance producer and the particular point of instantaneous power multiple, their overload characteristic relation curve of one of match on matlab;

(2) confirm the relational expression of the overload time and the overload magnification of resistance through the overload characteristic curve equation:

n ²*t＝676，

In the formula: n is an overload magnification, and t is an overload time;

(3) draw the value of overload magnification n by following formula:

n＝U ²/U _rate ²，

In the formula: U is the voltage that is added in the resistance two ends, U _Rate ²Rated voltage for resistance; Can satisfy the demand of corresponding occasion.

(4) by top relational expression, confirm the resistance overload magnification square is carried out integration, when integrated value greater than 676 the time, the newspaper overload, bright overload lamp stops discharge; Be treated in the program when the overload multiple greater than 1 the time, 1/200 of resistance overload magnification square is added up;

Through above-mentioned steps, realize protection control to the brake unit overload.

In above-mentioned steps (1), said overload characteristic relation curve can be n=26.8912*t ^-0.4-0.812, n is an overload magnification in the formula, and t is an overload time.

In above-mentioned steps (3), can adopt following method to obtain said U and U _Rate ²Value: U multiply by current duty ratio through real-time detection busbar voltage and draws U=U _Dc* DUTY; And U _Rate ²Rated power and resistance through resistance are calculated:

A mistake! Do not find Reference source.，

In the formula: P _RateBe resistance rated power, R is a brake resistance.

In above-mentioned steps (4), can adopt following formula to obtain said resistance overload magnification principal value of integral:

$N_{\mathrm{value}}=(n_1^2+n_2^2+n_3^2+...)*\frac{1}{200}\≥676,$

N _ValueBe resistance overload magnification principal value of integral, if n, representes then that resistance is in overload, then N always greater than 1 always _ValueValue adds up always, and 60S is a test period in program; If the state continuance 60S of resistance nonoverload, then clear N _ValueValue.

The present invention compared with prior art has following major advantage:

In order to improve the safeguard measure to brake resistance, the present invention simulates i ²The guard method of t.To the overload characteristic curve of brake resistance, overload magnification is done integration, when this integrated value exceeds the characteristic curve of brake resistance, the newspaper overload.Can quote overload timely through this method of experimental verification, well protect brake resistance.

With three-phase regulator frequency converter is applied triple point in the test, be connected on brake unit on the bus of frequency converter.Regulate the voltage of three-phase regulator, be controlled at 48%, 50% to the driving duty ratio of brake unit respectively, 75%, 100% four operating mode, and the operating time before their newspaper overloads added up.Statistics is as shown in table 2, and the brake unit of operating time and the Siemens of brake unit under each operating mode is much the same, and in the test, brake resistance is not all smoldered, and has obtained good protection.

Description of drawings

Fig. 1 for overload factor of the present invention and conduction time curve.

Fig. 2 is reduced equation of the present invention and particular point relation curve.

Embodiment

Below in conjunction with specific embodiment the present invention is described further.

Brake unit provided by the invention is crossed support method, specifically is to adopt the method that may further comprise the steps:

1. according to the overload capacity of brake resistance, match resistance characteristic curve.

Specifically: general brake resistance all has a momentary overload capacity, and table 1 has been set forth the overload magnification of the brake resistance that we select for use and the relation between the overload time.Therefore, we will protect brake resistance, will all be controlled at the operating condition of resistance in its technical indicator exactly, exceed just newspaper overload of technical indicator.According to the particular point of table 1, be abscissa with the overload time, be ordinate with the instantaneous power multiple.Their characteristic relation such as Fig. 1 of one of match on matlab.

Draw curvilinear equation: n=26.8912*t ^-0.4-0.812, n is an overload magnification in the formula, and t is an overload time.Be in dash area as long as guarantee the operating condition of resistance, then can guarantee the resistance nonoverload,, then report the resistance overload in case operating condition exceeds dash area.

2. the preliminary curvilinear equation of simplifying:

Because top equation calculates very trouble in the DSP the inside, simplify the curvilinear equation that draws with rounding trial and error procedure, because curve must be below particular point, therefore 26.8912 these coefficients are more little, curve can move down more.The big more curve of-0.812 this coefficient moves down more.-0.4 this coefficient is more little, and curve radian is more crooked.The curvilinear equation of the preliminary simplification that obtains thus is n=26*t ^-0.5

Draw new curve with the curvilinear equation of above-mentioned preliminary simplification, and compare, if find that this curve has been in the following of all particular points fully or through particular point, then this new curve satisfies the requirement to operating mode with particular point.

Can see curve or overlap like Fig. 2, or below particular point, explain that this curve satisfies the work operating mode, can be used as overload curves with particular point.

3. confirm the relation of overload magnification n and overload time t:

Drawn the relation of overload magnification n and overload time t through above two steps: if n ²* t＞=676 o'clock, newspaper brake unit overload.N in program ²* t can draw through square integration to the time of overload magnification.So crucial is exactly in program, to adopt following formula to detect the value of n in real time.

$n=\frac{P}{P_{\mathrm{rate}}},$

Wherein: P is current resistor power; P _RateBe resistance rated power.

Again because:

wherein R fixes, and is exactly the resistance of brake resistance.

So have: Wherein: U is the voltage that is added in the resistance two ends, U _RateRated voltage for resistance.

4. confirm the voltage U at resistance two ends and the rated voltage of resistance:

Owing to there not be in the program detection in real time to be added in the voltage at resistance two ends, so U can multiply by current duty ratio through real-time detection busbar voltage and draws U=U _Dc* DUTY.And that the rated voltage of resistance does not have on the resistance data yet is given, has only through the rated power and the resistance of resistance and calculates:

$U_{\mathrm{rate}}=\sqrt{P_{\mathrm{rate}}*R}.$

5. resistance overload magnification integration N _ValueConfirm:

The integrated value of overload magnification must satisfy: ∫ n ²Dt>=676

The program the inside can be expressed as n to the integration of overload magnification ₁ ²* t ₁+ n ₂ ²* t ₂+ n ₃ ²* t ₃+>=676.Since program the inside be every at a distance from 5ms to the busbar voltage once sampling, so following formula can be expressed as:

$N_{\mathrm{value}}=(n_1^2+n_2^2+n_3^2+...)*\frac{1}{200}\≥676$

If n, representes then that resistance is in overload, then N always greater than 1 always _ValueValue adds up always.60S is a test period in program.If the state continuance 60S of resistance nonoverload, then clear N _ValueValue.

6. detect N in the program always _ValueValue, when it surpassed 676, then newspaper transshipped, and bright overload lamp stops discharge.

Above-mentioned steps realizes the protection to the brake unit overload as a result.Test shows, this overload algorithm can effectively be protected resistance.Let resistance be operated under the operating mode of particular point, brake unit is all quoted overload and is stopped discharge with interior at overload time.Subordinate list

The technical indicator of the brake resistance in table 1 brake unit

Sequence number	Conduction time	The instantaneous power multiple
			1	1	26
2	2	20
			3	3	16
4	4	14
			5	5	13
6	10	10
			7	30	6
8	60	4.5
			9	180	2
10	300	1.5
			11	600	1.2
12	900	1.1

Test data under each operating mode of table 2 brake unit

Brake unit drives duty ratio	Brake unit overload time (s)
		48％	90
50％	83
		75％	25
100％	12.5

Claims (5)

1. a brake unit is crossed support method, it is characterized in that brake unit utilizes the momentary overload capacity of brake resistance to consume the power in the circuit in discharge process, reaches discharge effect; In order to guarantee that brake resistance is not burnt out in discharge process, the parameter of utilizing the producer of brake resistance to provide, the overload magnification of a brake resistance of match and the characteristic curve of overload time; If the resistance operating condition exceeds this characteristic curve, then report the brake unit overload.

2. brake unit according to claim 1 is crossed support method, it is characterized in that it specifically being to adopt the method that may further comprise the steps:

(1) overload time that provides according to resistance producer and the particular point of instantaneous power multiple, their overload characteristic relation curve of one of match on matlab;

(2) confirm the relational expression of the overload time and the overload magnification of resistance through the overload characteristic curve equation:

n ²*t=676，

In the formula: n is an overload magnification, and t is an overload time;

(3) draw the value of overload magnification n by following formula:

n=?U ²/U _rate ²，

In the formula: U is the voltage that is added in the resistance two ends, U _Rate ²Rated voltage for resistance;

(4) by top relational expression, confirm the resistance overload magnification square is carried out integration, when integrated value greater than 676 the time, the newspaper overload, bright overload lamp stops discharge; Be treated in the program when the overload multiple greater than 1 the time, 1/200 of resistance overload magnification square is added up;

Through above-mentioned steps, realize protection control to the brake unit overload.

3. brake unit according to claim 2 is crossed support method, it is characterized in that in the step (1), said overload characteristic relation curve is n=26.8912*t ^-0.4-0.812, n is an overload magnification in the formula, and t is an overload time.

4. brake unit according to claim 2 is crossed support method, it is characterized in that adopting following method to obtain said U and U in the step (3) _Rate ²Value: U multiply by current duty ratio through real-time detection busbar voltage and draws U=U _Dc* DUTY; And U _Rate ²Rated power and resistance through resistance are calculated:

，

In the formula: P _RateBe resistance rated power, R is a brake resistance.

5. brake unit according to claim 2 is crossed support method, it is characterized in that in the step (4), adopts following formula to obtain said resistance overload magnification principal value of integral:

，

N _ValueBe resistance overload magnification principal value of integral, if n, representes then that resistance is in overload, then N always greater than 1 always _ValueValue adds up always, and 60S is a test period in program; If the state continuance 60S of resistance nonoverload, then clear N _ValueValue.

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