CURABLE RESIN AND METHOD AND SYSTEM FOR INSULATING ELECTRICAL ITEMS THEREWITH

Abstract

A latent curable, single component, epoxy resin with a viscosity at 25° C. of between 50 and 100 poise may include, by weight: i) 60-90% of epichlorohydrin and bisphenol F; ii) 10-40% of epichlorohydrin and bisphenol A; and iii) 2-10% of a reactive catalyst, which is an encapsulated aliphatic polyamine, which cures above 80° C.

Claims

1. A latent curable, single component, epoxy resin with a viscosity at 25° C. of between 50 and 100 poise comprising, by weight: i) 60-90% of epichlorohydrin and bisphenol F; ii) 10-40% of epichlorohydrin and bisphenol A; and iii) 2-10% of a reactive catalyst, which is an encapsulated aliphatic polyamine, which cures above 80° C.

2. A latent curable, single component, epoxy resin as claimed in claim 1 wherein the aliphatic polyamine is a modified polyamine.

3. A latent curable, single component, epoxy resin as claimed in claim 2 wherein the aliphatic polyamine is modified, by one of: polyethylene polyamine adducts with nitriles, alkylene oxides, aldehydes, ketones, or mono and di-epoxides.

4. A latent curable, single component, epoxy resin as claimed in claim 1, wherein: the epichlorohydrin and bisphenol F is present in an amount of 70-90%.

5. A latent curable, single component, epoxy resin as claimed in claim 1, wherein: the epichlorohydrin and bisphenol A is present in an amount of 10-30%.

6. A latent curable, single component, epoxy resin as claimed in claim 1, wherein: the highly reactive catalyst is present in an amount, by weight, of between 4 and 8%.

7. An item of electrical equipment comprising a component which has been bonded to another component, coated, or impregnated with a resin, which is the catalysed reaction product of the epoxy resin of claim 1 and has an average molecular weight of less than 700.

8. An item of electrical equipment as claimed in claim 7, wherein the item of electrical equipment has been cured such that the resin has the following properties: TABLE-US-00002 Thermal Class UL1446 200° C. Shore D hardness DIN 53505 90 Deflection temperature IEC 1006 120° C. Bond strength IEC1033  23° C. >400N Twisted coil 155° C.  70N Elongation at break ISO 527 <0.5% Thermal Conductivity ISO 8894-1 0.4 W/M/K Dielectric strength IEC 60243-1 >200 kV/mm Dielectric constant IEC 250 3.9 @ 50 Hz Volume resistivity IEC 93 >10.sup.13 ohm/cm.sup.3

9. An item of electrical equipment as claimed in claim 7, wherein the item of electrical equipment is a rotary machine.

10. An item of electrical equipment as claimed in claim 9 wherein the rotary machine is one of: a motor comprising a stator winding and rotor, generator or alternator.

11. An item of electrical equipment as claimed in claim 7, wherein the item of electrical equipment is a static machine.

12. An item of electrical equipment as claimed in claim 11 wherein the static machine is one of: a static electrical winding, transformer, reactor, choke coil or inductor.

13. An item of electrical equipment as claimed in claim 7, comprising a conductive winding.

14. An item of electrical equipment as claimed in claim 7, wherein the item of electrical equipment is totally impregnated with the resin.

15. A product comprising an item of electrical equipment as claimed in claim 7, wherein the product is one of an industrial motor, traction motor, electric vehicle, automobile, home appliance or power tool.

16. A system for producing an item of electrical equipment as claimed in claim 7, comprising: i) a first heating chamber for pre-heating the item; ii) a tank for a resin; iii) an impregnation chamber; iv) a first vacuum pump operatively connected to the impregnation chamber; v) a second heating chamber for gelling the resin impregnated item; vi) one or more curing ovens; and vii) a cooling chamber where the item is cooled.

17. A system as claimed in claim 16, comprising a plurality of ovens.

18. A system as claimed in claim 17, comprising an item handler for conveying the item between the plurality of ovens.

19. A system as claimed in claim 16, wherein the first heating chamber is heated by magnetic induction.

20. A system as claimed in claim 16, wherein the tank for resin is an, as supplied, container of resin.

21. A system as claimed in claim 16, wherein the impregnation chamber comprises a centrifuge.

22. A system as claimed in claim 16, wherein the second chamber is heated by magnetic induction.

23. A system as claimed in claim 16, comprising controls facilitating the conveyance of the item to an oven, where the item is held for a given time at a given temperature such that curing is controlled.

24. A system as claimed in claim 16, wherein the cooling chamber further comprises an air compressor, air cooler and vacuum pump.

25. A method of treating an item of electrical equipment comprising a component, which requires an electrically insulating resin to be applied, the method comprising: pre-heating the item to a first temperature for a given time; applying an electrically insulating resin latent curable, single component, epoxy resin (14) with a viscosity at 25° C. of between 50 and 100 poise comprising, by weight: 60-90% of epichlorohydrin and bisphenol F; 10-40% of epichlorohydrin and bisphenol A; and 2-10% of a highly reactive catalyst, which is an encapsulated aliphatic polyamine, which cures above 80° C. to the item; ii) gelling the resin; iii) curing the resin by heating the item, in a stepped manner, to a temperature of at least about 165° C. to 200° C.; and iv) cooling the item.

26. A method as claimed in claim 25, further comprising removing excess resin before gelling the resin.

27. A method as claimed in claim 26, wherein removing the excess resin is done via centrifugation.

28. A method as claimed in claim 25, wherein the resin is applied to the item by one of: impregnation, brushing, spraying, dipping, rolling or trickling.

29. A method as claimed in claim 28 wherein the dipping is vacuum or vacuum and pressure dipping.

30. A method as claimed in claim 25, wherein the method uses impregnation.

31. A method as claimed in claim 30, wherein the impregnation is conducted in a vacuum.

32. A method as claimed in claim 30, wherein excess resin is removed from the item by centrifugation.

33. A method as claimed in claim 25, i) pre-heating the item to a first temperature for a given time in a first heating chamber; ii) heating the resin to a second temperature to reduce viscosity of the resin in a tank; iii) pumping the resin into an impregnation chamber, and impregnating the item with resin under vacuum; iv) emptying the impregnation chamber of resin; v) using a centrifuge to remove excess resin from the item; vi) gelling the resin impregnated item by heating the resin impregnated item to, at least, a temperature of about 130° C. to about 160° C. in a second heating chamber; vii) maximising polymerisation, by inline curing in one or more curing ovens with increasing temperatures for given times; and then viii) cooling the item to a temperature of in a cooling chamber.

34. A method as claimed in claim 33, wherein: the first temperature is about 50° C.; the second temperature is about 40° C.; the gelling temperature is about 130° C.; and the temperature is increased to about 165° C., and up to about 200° C.

35. A method as claimed in claim 33, wherein: the centrifuge operates at a speed of between 1000 and 2500 rpm.

36. A method as claimed in claim 31, wherein the vacuum pump operates at about 5 m Bar (500 Nm.sup.−2).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0097] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

[0098] FIG. 1 is an illustration of an exemplary item;

[0099] FIG. 2a is a schematic illustrating the system components;

[0100] FIG. 2b is a schematic illustrating the process steps;

[0101] FIG. 3 is a detailed illustration of the impregnation chamber, with centrifuge.

DETAILED DESCRIPTION

[0102] A typical latent curable, single component, epoxy resin (14) of the invention is provided in Example 1 below:

EXAMPLE 1

[0103] 60-90% by weight of epichlorohydrin and bisphenol F;

[0104] 10-40% by weight of epichlorohydrin and bisphenol A; and

[0105] 2-10% by weight of a highly reactive catalyst, which is an encapsulated aliphatic polyamine, which cures above 80° C.

[0106] A resin as per Example 1 is used to electrically insulate an item (10) as for example, illustrated in FIG. 1. The item is a rotor or stator comprising a component (12), in this case a copper winding (16), that requires to be insulated by treatment with the resin (14).

[0107] Referring to FIG. 2A the system/apparatus (100) for producing an item of electrical equipment (10) comprises:

[0108] a first heating chamber (110) for pre-heating the item;

[0109] a tank (120) for a resin (14);

[0110] an impregnation chamber (130);

[0111] a first vacuum pump (140) operatively connected to the impregnation chamber (130);

[0112] a second heating chamber (150) for gelling the resin impregnated item;

[0113] one or more curing ovens (160); and

[0114] a cooling chamber (190) where the item is cooled.

[0115] The cooling chamber further comprises an air compressor (170), air cooler (180) and vacuum pump (200). It may comprise a “fountain” contact mold with the circulation of a cold fluid.

[0116] The centrifuge (132), within the impregnation chamber (130), is illustrated in more detail in FIG. 3, however before describing it in more detail, the process of the invention is described with reference to FIG. 2B.

[0117] In general, the process comprises the steps of:

[0118] pre-heating (310) the item (10) to a first temperature (T1) for a given time (t1);

[0119] applying (330) a resin (14) of the invention to the item (10);

[0120] gelling (350) the resin;

[0121] curing (360) the resin by heating the item, in a stepped manner, to a temperature of at least about 165° C. and up to 200° C.; and

[0122] cooling (390) the item (10).

[0123] However, as illustrated across FIGS. 2A and 2B it comprises the steps of

[0124] pre-heating (310) the item (10) to a first temperature (T1) for a given time (t 1) in a first heating chamber (110);

[0125] heating (320) the resin (14) to a second temperature (T2) to reduce its viscosity in a tank (120);

[0126] pumping (322) the resin (14) into an impregnation chamber (130), and impregnating (334) the item (10) with resin under vacuum (340);

[0127] emptying (324) the impregnation chamber (130) of resin (14);

[0128] using a centrifuge (332) to remove excess resin (14′) from the item (10);

[0129] gelling (350) the resin impregnated item (10) by heating it to, at least, a temperature of about 160° C. in a second heating chamber (150);

[0130] maximising polymerisation, by in-line curing (360) in one or more curing ovens (160) with increasing temperatures (T) for given times (t); and then

[0131] cooling (390) the item (10) to a temperature of (Tr) in a cooling chamber (190).

[0132] The infusion chamber (130) with centrifuge (132) is illustrated in more detail in FIG. 3 where it is shown connected to resin tank (120) and with an item (10) held suspended, in an upright position along a rotor (136) axis (X-X), about which the item is spun. Connecting tubes (138a) facilitate filling (322) and emptying (324) of resin to and from the resin tank (120) and a separate tube (138b) leads to the vacuum pump (140). A large motor (133) drives the centrifuge and is located in a chamber (135) below the infusion chamber to provide stability.

[0133] Examples of items processed using the resins, system and methodology are further illustrated in Examples 2 to 5 below.

EXAMPLE 2

[0134] An Electric Motor Winding

[0135] The example given describes the impregnation of an electric motor stator winding. The stator, and associated winding, is of dimensions: internal diameter 100 mm, external diameter 150 mm, height 100 mm. It has a weight, with the copper winding, of 8.5 kg.

[0136] The item is processed in a system as described with reference to FIG. 2A.

[0137] The stator is pre-heated using magnetic induction. A localised magnetic field with a specific intensity and frequency) is applied to the stator. Induction also causes the heat to be transferred to the winding which is manufactured using materials with good heat conduction properties.

[0138] The resin is heated in its supply container (120), weight 25 kg. A heated strip maintains the resin at about 40° C. to ensure greater viscosity and optimum impregnation, and a mixing lid is used to keep the temperature uniform.

[0139] Impregnation occurs under vacuum to ensure any voids are completely filled. Excess resin is removed using centrifugal force (332). The impregnation chamber (130) is made of stainless steel and the centrifuge can spin to a rpm of 2200. The dimensions are sized in accordance with the item to be processed. A 5 m Bar (500 Nm.sup.−2). (residual) vacuum pump (340) is connected to the impregnation/centrifuge chamber.

[0140] Magnetic induction is used to heat the item to the gelling temperature, which is at least about 130° C. and up to about 160° C. This may take about 1 minute to ensure initiation of polymerisation. The item is then transferred to the curing ovens (160) where the item is processed for given times at constant temperatures which increase as the item is moved through the system.

[0141] The stator is preferably cooled by surface contact with a profiled mould, using liquids at varying pressure and temperature. A vacuum (200) process is used to remove condensate produced by low temperatures.

[0142] The system steps are performed in a fully automated manner without the need for an operator or intervention alongside, or linked to, a production line.

[0143] Illustrative cycle run times are indicated below:

[0144] 00:15—pre-heating of stator for 45 sec @5 kW. Temp. reached after 1 min delay 56° C.

[0145] 02:11—cable set up for impregnation (to prevent damage during spinning)

[0146] 02:40—valve check (open/close) for VOID preparation

[0147] 02:54—switch ON void pump

[0148] 03:00—vacuum level check on vacuum gauge

[0149] 03:07—vacuum level reached

[0150] 03:30—opening of resin INLET valve to fill the centrifugal tank (note that the resin is being sucked because of the vacuum)

[0151] 03:36—resin flowing through the connection from the tank to the vacuum tank

[0152] 03:48—resin level check from glass wall

[0153] 04:32—resin reaches desired level (just above winding head)

[0154] 04:35—resin INLET closure

[0155] 04:44—release of vacuum

[0156] 04:55—resin INLET valve re-opening in order to let resin flow out

[0157] 05:28—check that resin level is below mandrel

[0158] 05:44—centrifugation (5 sec to reach 2070 rpm; 10 sec spinning; 5 sec to reach 0 rpm)

[0159] 06:08—opening of centrifuge 06:32—drip check (no drips!)

[0160] 06:39—positioning for CURING process

[0161] 06:47—1st curing cycle 45 sec @5 kW, temp. reached after 1 min delay 91° C.

[0162] 08:36—2nd curing cycle 45 sec @5 kW, temp. reached after 1 min delay 135° C.

[0163] 10:20—3rd curing cycle 45 sec @5 kW, temp. reached after 1 min delay 165° C.

[0164] 13:36—visual check for dripping/resin status

[0165] 5:55—4th curing cycle 20 sec @5 kW, temp. reached after 1 min delay 180° C.

[0166] This illustrative impregnation process did not include cooling which requires a further, approximately 6 minutes.

[0167] The resin deposited on the component was about 80 grams and the process used about 500W, with cooling.

[0168] Whilst impregnation and centrifugation are favoured for the application of the resin, there are applications where this is not possible, as set out in Examples 3 to 5 below:

EXAMPLE 3

[0169] Motor Rotors

[0170] Very often the rotors on electric machinery have parts which do not require impregnation, for example shafts, contact manifolds and bearing seats, etc. For such items, a total impregnation technique cannot be used, and neither can the vacuum technique. Therefore, the trickling or rolling technique with the component in rotation must be used. Centrifugation is not required. The advantages remain the same.

EXAMPLE 4

[0171] Rotor and Stator Sheets

[0172] The system can be used to secure together sheets at the pack height required and if necessary attach permanent magnets at the same time. This procedure is ideal for automotive applications where complex profiles make it almost impossible, as well as being shunned by designers, to use traditional securing systems. Furthermore, this technology eliminates the need for insulated sheeting because insulation is applied during the securing and impregnation processes.

EXAMPLE 5

[0173] Transformers and Static Machinery

[0174] The process can be used for pre-heating, vacuum and pressure impregnation, with slow, or no, centrifugation, to protect heads.