The design of reactive shielded magnet clutches is considered along with their schematics, design formulas and characteristics of clutches in general. The design method suggested makes it possible to reduce calculation errors to 10%

Gertsov, S. M.

English

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s 1
NASA TECHNICAL MEMORANDUM 	 NASA TM 7552
THE DESIGN OF REACTIVE SHIELDED MAGNET CLUTCHES
S. M. Gertsov
(NASA-TM-75252) THE DESIGN OF REACTIVE N78-19511
SHIELDED MAGNET CLUTCHES (National
Aeronautics and Space Administration) 
1 0 13.I	 tlnclasHC A02/MF A01	 G3/37 08650
Translation of: "Raschet Reaktivnykh Mag-
nitnykh ekranirovannykh muft", Elektrotekh-
nika, No. 9, September, 1968, pp. 10-12.
19a N
w
1	 ^a
s^	 CIS^
NATIONAL AERONAUTICS AND SPACE ADUNI STRATION
WASHINGTON)
 D. C. 20546
	 MARCH 1978
https://ntrs.nasa.gov/search.jsp?R=19780011568 2020-03-22T04:18:43+00:00Z
STANDARD TITLE PAGE
h
.
1. Resort ate. 2. Government Accession No. 3. Recipient's Catalog Me.
NASA TM	 75252
4.	 Title and Subtitle S. fe°bruary, 1978 .
The Design of Reactive Shielded Magnet 6 .
 Porlwiming Orsoftization Dada Clutches
7.	 Author(s) s. Perforating Organisation Rose" He.
S. M. Gertsov
10. work Unit He.
11. Contract or Grant No.
NASv-27919. Performing Organization Name and Address
SCITRAN 13. Tree of Report end Period Covered
isox 5456
Santa Barbara
- 
CA	 931AR Translation
12.SPynsering A en y Name end Address
ationa^ l^ieronautics and Space Administration
Wastungton, D.C.	 10546 14. Sponsoring Agency Coda
15. Supplementary Not**
S
Translation of "Raschet Reaktivnykh Magnitnykh Ekranirova.nny
muft",Elektrotekhnika, No. 9, September, 1968, pp. 10-12.
16. Abstract
Design of reactive shielded magnet clutches; ahematics, de-
sign formulas and characteristics of clutches; method sug-
gested makes it possible to reduce calculation errors to
10%.
17. Key words (Solsctod by Author($)) Is. Distribution Statement
	
This copyrighted"
Soviet work is reproduced and sold
by NTIS under license from VAAP, the
Soviet copyright agency. 	 No further
copying is permitted without per-
mission from VAAP.
19.	 Security Ciossif. (of this report) 20. Security cloesil. (of this PW) 21. No. of Poges 22.	 Prise
Unclassified Unclassified 10
LIQ 	 _•....	 ,^ ,.
THE DESIGN OF REACTIVE SHIELDED MAGNET CLUTCHES	 /10*
S. M. Gertsov**
A technique for designing reactive, shielded magnet
clutches is presented. The error of the design does
not exceed 10%.
Shielded magnet clutches (SMC's) have found wide application in
the chemical branch and in a number of other branches of industry for
the transmission of synchronous rotation into a corrosive medium, va-
cuum, and so on.
There are a number of SMC constructions, which can be divided in-
to three basic classes on the basis of the nature of the moment which
is generated: active constructions, with the interaction of two magnets
(Figure la); reactive constructions (Figure lb), in which the moment is
generated due tc the difference of the permeances in the gear air space
along the longitudinal and lateral axes; hysteresis constructions (Fig-
ure lc) which create the moment due to loss in the hysteresis layer.
The fundamentals of the theory of reactive SMC's are given in
[1]; however, this reference contains no practical technique for de-
signing SMC's. This deficiency is partially compensated in [2], but
in this reference, the calculation of the magnet circuit of the SMC
is made very roughly, without an accurate determination of the per-
meance of the gear zone. In this article, we present a comparatively
simple technique for designing reactive SMC's that ensures a high de-
gree of accuracy for it.
Reactive SMC's have the following advantages over active SMC's
in a number of cases; 1) a smaller mismatching angle of the guiding
and guided parts; 2) they allow turning of the guided part relative
*Numbers in margin indicate pagination in the foreign text.
** Candidate of Technical Sciences
1
to the guiding part without noticeable demagnetization of the magnet;
3) they make it possible to use magnets of _ %elatively simple form with
high magnetic energy.
I	 .7
a	 b
c
	Figure l: Types of clutches. a) active	 b) reactive
	 c) hysteresis
1- magnet	 2- shield
	 3- hysteresis layer
	 4- cap of mag-
netically soft steel
	 5- external part of magnetically soft
steel.
Once the dimensions are chosen, the design of a shielded magnet
clutch reduces to determining the maximum static moment which can be
transmitted by the clutch. The dynamic moment, which determines the
working properties of the SMC, is less than the static moment by a
quantity equal to half of the moment of the loss in the shield [1].
However, when the shield is designed from nonmagnetic steel of brand
lX18H9T or the titanium alloys BT -3, BT-5, the moment of the loss in
the shield is insignificant (with the rotational speeds and thicknes-
ses of the shields which are usually found).
The calculation of the maximum static moment begins with the
energy balance of the system. In a reactive SMC, there is a change in
magnetic energy when one part of the clutch is turned relative to the
other. It is obvious that the mechanical work produced during this
turning will be equal to the change in the magnetic energy:
	
-A,, - AA MA. II•	 (1)
We will consider the change in the magnetic energy of the clutch.
A graph of the magnet is presented in Figure 2. The magnetic flux of
the magnet is plotted along the axis of the ordinates, and the magne-
tizing force is plotted along the axis of the abscisses.
T.
2
'e
We will assume that the SMC is magnetized in the assembly (which
is in fact usually the case). Immediately after the magnetization, the
position of the point r is determined by the longitudinal permeance
of the clutch Gd , i.e., by the permeance with the matched position of
the gears. When the internal part of the clutch (the rotor) is turned
Y
Figure 2: Graph of the magnet
relative to the external part (which we will call the stator) by the
angle	 i.e., when it is turned into the position of maximum mis-
matching of the gears, the position of the operating point A will be
	 /11
determined by the lateral permeance of the clutch G q . When the rotor
of the SNIC is returned to the initial position, the point A moves along
the return line to the point E. The area of the shaded triangle AOE
determines the change in the magnetic energy of the system in turning
the guiding part relative to the guided part by the angle n_-" 	 This
change in the magnetic energy is determined from the following relation:
(P„	
ad-7- a"	 (2)
where	 is the reference flux (Figure 2);
S is the return coefficient.
As experiments show, the dependence of the static moment of the
clutch on the electrical mismatch angle za is practically sinusoidal:
I" : AAA.,, sM :a,
where z is the number of gears on each part of the clutch.
The work which we are looking for will then be determined from ex-
pression (3):
3
c )RIGMAL PAGE I5
OF PWR QUALITY
a _. X_
r
1
Ame I --	 .1"Milo, "III ( :a) 11i
-O	 (3)11	 ^.Iwp.-'il• w il lti	 -	 2
By solving (1) - (3) simultaneously, we will obtain an expression
for the maximum static moment of the clutch:
Qd 
— 
(iq (4)
Thus calculating the maximum static moment reduces to determining
the longitudinal and lateral parmeances of the air gap. This problem
has been successfully solved by a number of authors for inductor gene-
rators and step electric motors. However, due to the presence of the
shield, the relative air gap in the magnet clutch may be much greater
than those examined in these references.
Diagrams of the magnetic field for various values of the relative
air gap and angle of mismatching, as well as for various widths of the
gears, were constructed to determine the specific permeance of the
gear air gap.
The diagrams of the field were constructed by modeling on current-
conducting paper by means of the EGDA-9/60 integrator [3]. As an exam-
ple, the field diagrams are presented in Figure 3 in the matched and
the mismatched position of the gears with a relative air gap of d'
0.15; 6' = a t is the gear scale; d is the air gap.
Figure 3: Field Diagrams in the air gap.
The dependences of the specific permeance (the permeance for one
gear division per unit length) on the relative size of the air gap for
the three values of the width of a gear 	 (0.3; 0.4; 0.5)t are pre-
sented in Figure 4.
4
-^-^ Pr.5 -r ^ ^i
tr^l.^d-r,^sllf.t
I is	 J 2S	 , 3S
m "nn/o .."
,9
9
7
6
S
4
2
OS
The total permeance is determined as the product of the specific
permeance per length of the gears I. and the number of gears; in con-
nection with the fact that the reactive SMC depicted in Figure lb has
two operating air gaps, the value of the permeance which is obtained
is decreased by a factor of two.
'^ 94
14
1?
10	 0,=U3t
9	
0,=0,4t
4
it
1
J,03	 a 13	 U, 23	 //,JS
Figure 4: The change in the longitudinal specific permeance g d (for 1
gear division and 1 cm length) and the lateral specific per-
meance g  as functions of the relative air gap d'.
Thus, the total permeance of the air gap is
swL 
	
(5)
It is more convenient to carry out the calculation of the maximum
static moment.in relative units. In this case, the graph of the mag-
net is constructed in relative units.
The values of the permeances in relative units are determined in
the following way:
G,	 ll,•rJ -- 1 3rJ
m 
^
G, - G ll^l„
^ _ q RrS„„, •
(6)
5
where H,.a, are the coercive force and the residual magnetic induction
of the magnet;
i,„.s. are the length and cross-sectional area of the magnet.
When the calculation is carried out in relative units, the value
of the maximum static moment is determined from expression (7):
""' )2
 
c G'
..
  ((;'
	 (7)
Choosing the number of gears and the geometrics of the gear zone.
In contrast to the inductor generators and step electric motors, where
the number of gears is uniquely determined by the given frequency of
the patch angle, the number of gears in reactive SMC's, as a rule, is
not limited by output parameters. In choosing the number of gears,
one therefore tries to obtain the greatest transmittable moment in the
given dimensions, or the minimum dimensions of the SMC with a given
maximum static moment.
To determine the optimal number of gears, we will examine an elec-
tromagnetic clutch for which the magnetizing force is constant (F =
const). The following dependence is ,justified for it:
r= 116
	
r, =z
Since G,t- G,,—z^(gj_bro), by setting we conclude that the max-
imum static moment is proportional to the square of the number of gears
and to the change in the permeance of the air gap:
Almon = ASq.
It is necessary to find the maximum of the expression z 2Aq as a /12
function of the relative air gap 61.
In the general case, it is necessary
 to express the function tag-1(6')
analytically to solve this problem. Since this function is essentially
non-linear, an approximation of it will inevitably lead to additional
errors. Therefore, a number of particular solutions for expression (8)
have been found, and the dependence
Z'k,- 101
has been constructed for the values found. This dependence has been
determined for the three values of the width of a gear N - (0.5; 0.4;
0.3)t; for generality of the solution, a number which is a multiple
ORIGINAL PAGE IS
OF. POOR QUACK6
h.I
1
,
of the number of gears z'; z' is used instead of z; z' takes the
values of 1, 2, 3...
The dependences which are obtained are presented in Figure 5. An
0 /1,25 0,1 n, ,S 07 0,73 0,3 A.V
Figure 5: Determining the optimal number of gears.
analysis of these dependences has shown that for n., = 0.5t, the func-
tion is maximal at 6' = 0.075; for n:.= 0.3t and r,.,= 0.4t, the maximum
of the function is located at d' = 0.15; here the greatest value of
the function is reached at 6, = 0.4t.
We can thus draw the following conclusions.
1) the optimal width of a gear must be 0.4 of the gear division,
i.e.,	 b:, - 0.4t.
2) here the number of gears must be chosen so that the relative
air gap is d' = 0.15;
3) the height of a gear must not be less than half of the gear di-
vision [3]; a., > t/2;
4) the permeance of the gear zone does not change significantly in
varying the inclination angle of the edges of a gear by + 10%.* It is
therefore advisable to choose this angle in the range 7-10 0 to decrease
the saturation of the base of the gear.
Choosing the principal dimensions of the clutch. An analysis of
equation (7) shows that the expression
,	 c"r — 
Ir,1.	
(9)
which is proportional to the area of the triangle AOE (Figure 2) has
its greatest value in the case where the SMC is operated near the point
*A. A. Terzyan. Induktornyy generator s pul'siruyushchim potokom (An
inductor generator with pulsed flux). Candidate's disdertation,
1963.
7
Fof the maximum energy of the magnet R , i.e., between the points .1 and
s.
Expression (9) is strictly determined and is equal to 0.1119 for
an optimally designed reactive SMC. On this basis, it is easy to
tnansform equation (7) into the formula of a machine constant for a
reactive SMC:	
p
k,kp/3r11,,	 (10)
where	 11	 is the fullness factor of the magnet in relative units;
k,-s,^ID'm is the coefficient of the geometry of the magnet;
k r =D r/D ,. is the ratio of the diameter of the rotor to the dia-
meter of the magnet.
For a gap of 0.1 - 0.2 cm; k  = 1.1 - 1.3.
Expression (10) makes it possible to determine the principal dimen-
sions of the clutch as a function of the transmittable moment and the
properties of the magnet. After determining the diameter and length
of the magnet and choosing the number of gears, we can calculate the
length of the gears from the following considerations; the require-
ment G  ti 0.92 must be satisfied for operation near the point of maxi-
mum energy; the total lateral permeance G  can be found from expression
(6) and the length of the gears, from (5).
The technique that has been proposed makes it possible to design
reactive SMC's with an error that is not greater than 10%. This has
been verified on a number of manufactured clutches.
LITERATURE
[1] Glukhanov, N. P., Shielded Synchronous Clut:hes with Like Poles.
Trudy VNIITVCh, 1965, No. 6.
[2] Ginzburg, L. B., Designing a Shielded Synchronous Clutch with Like
Poles. Trudy VNIITVCh, 1965, No. 6.
C3] Fil'chakov, P. F., Pan'chishin. IntegratoryInterat  EGDA. Modelirovaniye
otentsial'n kh poleX na elektro rovodno buma e.	 EGDA inte-
grators. Modeling of otent a Fields on Electrical-Conducting
Paper). AN USSR, 1961.
8


The design of reactive shielded magnet clutches

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