TK Torque Motors

Torque and Spindle Motors

The TK series of frameless brushless motors provide the highest torque density available today for direct drive, high performance applications.

TK Torque Motors are three phase, rare earth (Iron Neodymium Boron) permanent magnet units and reach the highest continuous and peak torque density available today.

Unlike traditional torque motors, TK units have both high torque and high speed capability and thus operate seamlessly both as spindle and rotary table motors.

The rotors use special Phase manufactured magnets with minimized loss factor allowing high speed operation with a thin isotropic rotor.

TK motors are three phase, rare earth (Iron Neodymium Boron) permanent magnet units and reach the highest continuous and peak torque density available today, together with high speed and flux control ability over a constant power range up to 10:1.

TK Torque Motors consist of stator and rotor units supplied separately suitable for direct mounting inside the machine structure.

All rotors are rigid units with mechanical, glue free magnet retention, preloaded carbon fiber sleeve for safe operation even at very high speed.

HOW TO CHOOSE THE RIGHT MOTOR

PRELIMINARY MOTOR DESIGN TOOL

TK CONFIGURATOR

Rotor are often semi custom units to allow direct coupling to bearings, encoders, brakes.

Customized frames with integral cooling or even partial machine subassemblies with bearings and encoders are manufactured on request based on the standard frameless magnetic designs available.

All TK Torque Motors are designed for fluid (water) cooling on the outside of the stator for maximum performance. Conduction/convection cooling is also possible.Constant power operation (flux control) always requires water cooling.

Torque Motor code	Stack [mm]	L tot.[mm]	Øout [mm]	Øin [mm]	Torque (Water Cooled) [Nm]	Torque (Air Cooled)[Nm]	Peak Torque [Nm]	Nominal Speed (rpm)	Max Speed (rpm)
TK.085	50	110	96	44	7,30	3,70	24,10	5000	18000
	100	160	96	44	16,20	8,10	48,20
	150	210	96	44	25,40	12,70	72,30
	200	260	96	44	34,70	17,40	96,40
TK.110	50	125	121	43	12,50	6,30	33,20	5000	20000
	100	175	121	43	26,90	13,50	66,30
	150	225	121	43	41,60	20,80	99,50
	200	275	121	43	56,30	28,20	132,70
TK.120	50	125	134	54	21,90	11,00	47,50	5000	15000
	100	175	134	54	48,20	24,10	95,10
	150	225	134	54	75,10	37,60	142,60
	200	275	134	54	102,40	51,20	190,00
TK.164	50	125	173	76	48,30	24,10	93,50	4000	10000
	100	175	173	76	104,70	52,30	187,00
	150	225	173	76	162,10	81,10	280,40
	200	275	173	76	219,90	110,00	374,00
	300	375	173	76	336,00	168,00	560,90
TK.188	50	140	202	80	34,80	17,40	119,50	6000	28000
	100	90	202	80	79,10	39,50	238,90
	150	240	202	80	125,80	62,90	358,40
	200	290	202	80	173,60	86,80	477,80
	300	390	202	80	270,50	135,20	716,80
TK.195	50	160	207	76	49,50	24,80	93,50	2000	15000
	100	210	207	76	108,69	54,30	187,00
	150	260	207	76	169,20	84,60	280,40
	200	310	207	76	230,20	115,00	374,00
	300	410	207	76	352,70	176,40	560,90
TK.220	50	170	240	110	75,60	37,80	159,00	3000	14000
	100	220	240	110	172,40	86,20	318,10
	150	270	240	110	274,40	137,20	477,10
	200	320	240	110	378,70	189,30	636,20
	300	420	240	110	590,10	295,10	954,30
TK.240	50	135	249	142	111,20	55,60	216,50	3000	8000
	100	185	249	142	240,00	120,00	433,00
	150	235	249	142	371,30	185,60	649,40
	200	285	249	142	465,90	251,60	865,90
TK.270	50	140	282	160	112,30	56,20	282,70	3000	8000
	100	190	282	160	253,00	126,50	565,50
	150	240	282	160	399,30	199,60	848,20
	200	290	282	160	547,70	273,90	1.131,00
TK.310	50	120	310	198	215,60	107,80	373,90	500	3000
	100	170	310	198	475,90	238,00	748,00
	150	220	310	198	743,30	371,70	1.121,80
	200	270	310	198	1.013,00	506,60	1.495,70
TK.340	50	145	358	190	242,00	121,00	407,20	2000	6000
	100	195	358	190	547,20	273,60	814,30
	150	245	358	190	864,70	432,40	1.221,50
	200	295	358	190	1.186,90	593,50	1.628,60
	300	395	358	190	1.837,00	918,50	2.442,90
TK.370	50	140	380	268	271,70	135,90	636,20	1000	4000
	100	190	380	268	604,50	302,20	1.272,30
	150	240	380	268	947,40	473,70	1.908,50
	200	290	380	268	1.294,00	647,00	2.544,70
	300	390	380	268	1.991,40	995,70	3.817,00
TK.450	50	170	465	320	468,20	234,10	916,10	1000	3000
	100	220	465	320	1.033,70	516,90	1.832,20
	150	270	465	320	1.613,00	806,50	2.748,30
	200	320	465	320	2.196,90	1.098,40	3.664,40
TK.485	50	145	485	345	544,00	213,00	1.068,00	1000	2000
	100	195	485	345	1.197,00	500,00	2.136,00
	150	245	485	345	1.858,00	802,00	3.204,00
	200	295	485	345	2.521,00	1.110,00	4.272,00
TK.540	50	145	548	400	712,80	356,40	1.431,40	400	1500
	100	195	548	400	1.547,50	773,80	2.862,80
	150	245	548	400	2.397,40	1.198,70	4.294,20
	200	295	548	400	3.252,00	1.626,00	5.725,60
TK.570	50	115	578	450	745,40	372,70	1.767,10	400	1500
	100	165	578	450	1.673,00	836,50	3.534,30
	150	215	578	450	2.632,50	1.316,20	5.301,40
	200	265	578	450	3.603,60	1.801,80	7.068,60
TK.795	50	160	815	640	1.631,10	815,50	3.365,40	200	800
	100	210	815	640	3.781,20	1.890,60	6.730,70
	150	260	815	640	6.063,60	3.031,80	10.096,10
	200	310	815	640	8.402,10	4.201,10	13.461,40
TK.1150	50	190	1210	908	3.495,00	1.785,00	6.789,00	100	400
	100	240	1210	908	7.996,00	4.281,00	13.577,00
	150	290	1210	908	12.696,00	6.952,00	20.366,00
	200	340	1210	908	17.457,00	9.695,00	27.155,00
TK.1340	50	190	1420	1100	4.542,80	2.271,40	9.842,30	100	400
	100	240	1420	1100	10.639,40	5.319,70	19.684,60
	150	290	1420	1100	17.147,10	8.573,50	29.526,90
	200	340	1420	1100	23.831,50	11.915,70	39.369,20
TK.1700	50	190	1770	1420	8.113,80	4.056,90	15.946,80	100	300
	100	240	1770	1420	18.951,20	9.475,60	31.893,50
	150	290	1770	1420	30.480,20	15.240,10	47.840,30
	200	340	1770	1420	42.301,80	21.150,90	63.787,00
TK.2000	50	260	2085	1700	8.587,40	4.293,70	23.004,10	100	300
	100	310	2085	1700	20.713,90	10.356,90	46.008,20
	150	360	2085	1700	34.103,80	17.051,90	69.012,30
	200	410	2085	1700	48.132,40	24.066,20	92.016,40
TK.3080	50	260	3170	2760	24.318,60	12.159,30	51.035,20	100	250
	100	310	3170	2760	57.331,50	28.665,80	102.070,30
	150	360	3170	2760	92.790,20	46.395,10	153.105,50
	200	410	3170	2760	129.340,00	64.670,00	204.140,70

Motor morphology and application guidelines

TK motors consist of:
A three phase stator, wound and impregnated (3 dips, preferred solution for high thermal cycling), or vacuum encapsulated in super high thermal conductivity compound (for low surface temperature operation), which is either built into a thin steel microframe, cylindrical, or into a metallic frame carrying the cooling chambers and coupling O-Rings on the outside and a set of tapped holes on one side (Squid type).

The microframe units are ground to h7 tolerance on the outside diameter and are machined parallel on the two stack sides. This construction is intended for interference fit or axial pressure locking.

The microframe technology maximizes the usage of space in the assembly and requires the machine body to carry the cooling cavities on the inside. It requires some care in the design of the application but results in the highest space and power density today possible.

Alternately, the SQUID frame is much simpler to use and only requires a cylindrical cavity, while motor assembly and fastening s just through a set of screws. The achieved torque density is slightly inferior to the microframe due to the radial size of the frame.

The insulation system of the motors is rated Class H (magnet wire: Class C) with reinforced insulation specifically designed for the high DV/dt typical of 600 Vdc servo drive application; the windings are equipped with three PTC sensors for protection and a KTY 84 linear temperature probe for process monitoring.

The star point of the winding is also generally available for filtering purposes. All windings are factory tested for insulation 4.5 kVdc to ground and 3.5 kVdc phase to phase, far in excess of regulation requirements.

A Permanent Magnet Rotor, with tubular, isotropic base shape, which carries the magnets on the outside periphery, protected by a preloaded carbon fiber (up to 150 m/sec) ring.

The magnets are generally high temperature, high energy FeNdB sintered magnets, Phase Motion Control manufactured with a special patented technology. They are designed for the maximum class temperature and are virtually impossible to demagnetise except in case of drive failure or improper operation. If continuous exposure to oil is forecast, special oil resistant magnets can be specified.

The rotor may be fastened on the shaft either by interference fit or by an array of axial bolts. The latter construction is preferred for high torque, low speed applications such as rotary tables. In general, the rotor inside profile is customised to fit with the needs of the machine provided the required profile is compatible with the maximum hole required by the magnetic field, and specified in the accompanying technical sheets.
For proper operation, the motors need a position sensor on the shaft (not supplied) both for field orientation and for position/speed control.
The rotor is permanent magnet type and has no primary losses, so that no rotor cooling is needed in principle. However, the inverter chopper frequency must be set high enough to ensure that the ripple current, pk-pk is less than 20% of the nominal rms current to avoid the insurgency of unacceptable, and dangerous, stray rotor loss.

Customized frames with integral cooling or even partial machine subassemblies with bearings and encoders are manufactured on request based on the standard frameless magnetic designs available.
The rotors are supplied not balanced; high speed operation requires dynamic balancing when assembled on the application shaft.

Depending on their geometry and magnetic circuit, TK motors can be divided into three main branches:

Thin ring, large diameter motors for high torque, low speed (torque motors)

Typical applications:

Rotary tables for NC machine tools, often with turning capacity
Indexers for transfer machines
NC machine head orientation
Large rotary tables (glass, packaging, assembly)
Carbon fiber deposition machinery
Direct drive of mills (concrete, ceramics, rubber
Large low speed generators (mini hydro, wind power)
Metal forming: electric press and bending
Direct drive plastic injection machines

In all these applications, direct drive eliminates play and removes the need of an accurate mechanical gearbox, which in turn would limit the accuracy and the dynamic performance of the system. Mechanical brakes-dividers are unnecessary. The table accuracy is the accuracy of the encoder system. The system is thus extremely simple, flexible and reprogrammable.
The removal of the transmission system and of its backlash and elasticity results in control bandwidth up to 250 Hz, so that a positioning cycle can be completed with great accuracy within a few msec with advantage on the machine cycle time. To ensure adequate servo performance in direct drive high accuracy, high stiffness applications such as indexing and rotary tables in NC machine tools, the sensor must be sinusoidal so that the drive may interpolate the actual position with a resolution at least ten times greater than the required accuracy. Additionally, the sensor fastening or spring mount must have intrinsic resonance frequency above 2000 Hz not to limit the overall system performance.

Spindle motors for mills and lathes

long and thin motors, brushless with flux control ability, medium to high speed, high power density, suitable for heavy machining or control of large inertia loads for spool winding/unwinding. The TK motors have currently the highest power density and allow the manufacture of electrospindles with torque rating hiterto unattainable, in the range of several thousand Nm while reaching high speeds in the thousands of rpm. Spindle type motors are anyway high performance servo motors so another emerging application area is very short cycle actuation. Recent application are in direct drive of the ram of high speed turret punching press with stroke rates in excess of 300 strokes/min, or fast, heavy indexing in wire frame welding machines.

Typical applications:

Power lathes for automotive,
Spindle motors for mills and high speed machining centers
Wire grid manufacturing

Tube motors, small diameter, for multiple spindle units

Typical applications:

High speed/power motors where lateral (pitch) space is limited
Multiple drilling heads
Swiss type lathes

Standard size of terminal cables vs nominal motor current
PTFE insulation, 2500 Vac, L=500 mm
Nominal current	Wire size
In < 15 Arms	1.22 mmq = AWG 16
15 Arms <= In< 25 Arms	2.97 mmq = AWG 12
25 Arms <= In< 45 Arms	8.6 mmq = AWG 8
45 Arms <= In< 82 Arms	15 mmq
82 Arms <= In< 110 Arms	25 mmq
110 Arms<=In< 200 Arms	50 mmq

How to choose the optimal TK motor?

First, define the technical feasibility of the application. In general, all motors share the same physical limitation, that is, the ability to generate “airgap thrust”, i.e. a sideways thrust between stator and rotor which is linear thrust in linear motor, and becomes a torque when the motor is round. The amount of thrust per unit area depends on motor technology but is fundamentally limited by the properties of the materials (magnets, copper, steel) used in the motors. PM technology offers the highest specific thrust available today, and this value is gradually increased as the technology improves. Many factors (cooling conditions, size, airgap thickness, linear speed etc.) affect this value which should only be used as a rough guideline. Tk rotary motors and Wave linear motors are characterised by a peak thrust around 8000 N/m2, continuous thrust with water cooling ~ 5500 N/m2.

The thrust limitation explains why it is always appropriate to use the maximum diameter available to maximize output torque. In general if a motor is scaled in diameter, torque is scaled with the square of diameter, while it scales only linearly in length. Consequently, to verify whether a new application is feasible at all, if the torque availability is expected to be a limitation, the maximum diameter available should be determined compatibly with physical limitation and maximum peripheral speed (values below 150 m/sec pose no problem) and the airgap surface can then be evaluated. This would give a rough estimate of motor length and therefore indicate whether the application is feasible or not.

Large rings with very limited axial length are the most efficient solution for high torque low speed applications, and they have the additional advantage of not needing separate bearings as they can be generally carried by the same bearings of the load. However, inertia scales with the cube of diameter, so where the inertia is the dominant load, long and thin motors are more appropriate. A typical example is the direct drive of the ram of high speed punch presses, in which motion is reversed over 300 times/min, or in high speed flying shears; in this case, tubular, water cooled TK motors provide the highest performance solution.

Spindle drives generally demand both high torque and high speed but the diameter is generally restricted, so they tend to be long and thin. Airgap hole diameter to length ratios up to 1:3 are routinely manufactured. In this case, the Phase PM magnet technology allows the manufacture of extremely thin stators and rotors which are particularly useful in multispindle applications.

Spindle PM motors manufactured with the high frequency Phase magnetic technology can operate both in constant torque and constant power mode. The constant power range, depending on the type, can exceed 10:1 although this is generally limited by the ability of the drive selected to control a deep deflux range.

When compared to AC Induction spindle motors, the PM motor design offers:

Rated torque approximately double in the same size
Larger shaft compared to the outer diameter
Loss only limited to stator, rotor is “cool” so that bearings can operate more accurately and reliably
Solid, “mechanical” rotor (non laminated) which guarantees balancing stability
Wide constant power control range (up to 10:1) without tap change
Free from radial flux which may generate currents in the bearings

In the Phase TK technology, there is no fundamental physical difference between torque motors and spindle motors; they have the same smoothness and high bandwidth necessary for direct drive indexing and contouring operation, so that milling and turning operations on the same motor are now possible.

There is, however, a fundamental difference between PM and induction spindle drives. In the induction technology, power is used to magnetize the motor (at low speed, high torque) thus resulting in limited output torque available; flux reduction is easily obtained by just reducing the magnetizing current.

Thus the motor is “hot” at max load, and “cool” at no load. PM motors, conversely, derive the field from high energy permanent magnets, so that no power is required to build the motor field and more power can be devoted to torque generation. When the flux must be reduced, however, power must be applied just to lower the field so that PM motors at high speed need some current even at no load.

A typical power and torque curve versus speed is shown in Fig. 1 for a combined torque/spindle motor with 570 mm diameter, 100 mm axial length; in Fig. 2, the motor temperature at no load and full loads are displayed. It can be observed that above the “knee speed” i.e. the speed of transition between constant torque and constant power operation, the motor temperature becomes progressively independent of motor load.

Mechanical Assembly, airgap control and magnetic attraction

Another useful feature of PM technology is the ability to operate with a wide airgap, up to several millimetres in the larger motors. This feature can be useful in machines with important deformations, such as plastic injection press or impact hammers. As a standard the airgap is in the order of 1 mm, radial, and this generally enables designs in which the motor rides on the machine supports without need of separate bearings.
The magnetic flux in the rotor generates radial attraction forces.

These are perfectly balanced only if the rotor sits in the center of the stator, and increase with eccentricity. In practice, this is equivalent to a “negative stiffness” which must be compensated by a much higher positive stiffness in the bearing system. The attraction data can be supplied on demand, the order of magnitude is shown in the graph in Fig. 3, for a 1000 Nm, 370 mm diameter, 105 mm long torque motor with a 1 mm radial airgap.

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