S K Dynamics

Motors and Controls Technology / Products

S K Dynamics Pvt. Ltd. (SKD) is Technology provider to Analog Devices Inc. USA in the field of Motor Controls since 1994. ADI is the first to introduce DSP micro-controllers (ADMC3xx) for motor control applications. SKD has made significant contribution in the design and development of world’s first DSP Micro Controller (ADMC315) dedicated for Motor control applications introduced by ADI in 1996.

Different types of Motors and Motor Controllers designed and developed by SKD are described below.

Type of Motors

DC Brush Motor

AC Induction Motor (ACIM)

Permanent Magnet Synchronous Motor (PMSM)

Brushless DC Motor (BLDC)

Switched Reluctance Motor (SRM)

Stepper Motor

Motor Configurations

Conventional Configuration (Outer Stator)

Outer Rotor Configuration

Pancake / HUB Motor

Linear Motor

Low Inertia / Coreless Motor

High Inertia / Gyro Motor

Motor with Internal Planetary Gear Assembly

General Range of Motors

Capacity: 2 W to 12 HP (9000 Watts)

No. of Poles: 2 to 100

No. of Phases: 2, 3, 4

Type: DC / ACIM / PMSM / BLDC / SRM / Stepper

Configuration: Outer Stator / Outer Rotor / HUB / Inertia

Weight to Power Ratio: up to 1 Kg/ HP

Type of Gearbox: Internal / External / None

General Range of Controllers

Control Dynamics: Two Quadrant / Four Quadrant

Breaking: Regenerative / Dissipative

Electrical Frequency: up to 1000 Hz

Interface: Analog, Digital (TTL), Communication

Control Parameters: Position, Velocity, Acceleration

Control Technique: Sensorless or 1 or 3 Sensor(s)

Multi-Drive Control: 1 to 62 Drives from 1 Master

Power Source: 6V to 350V DC, 110V / 220V AC

The Motors and Controls or Drives can be customized as per the application and find use in Commercial, Industrial, Military and Avionics applications. The motors are lightweight having high efficiency as well as multiple control interface

AC Induction Motor Control for Washing Machines

In production by Frigidaire - USA

The first generation control for ACIM based washing machine was developed by SKD (1998-99) and is in production now

by Frigidiare, USA. A total production of 460,000 units was made by Frigidiare, USA during the year 2000. The next

generation control for this washing machine was alsodeveloped with additional features and lower cost. Over

1 Million machines have been sold in US market till date.

Salient Features

Optimized processor for motor control application

Wide range Speed Control 200 to 16000 rpm to give efficient washing control during Tumble/ Spin

Timer Motor Control

Data Recovery during Power Failure

Unbalance detection and re-distribution

PMSM Sensorless Control for Refrigerators

In production by Sharp - Japan

The control Solution for a Sensorless PMSM was developed by SKD in the year 1996 which was modified and tuned for a refrigerator compressor control by 1998. The Sensorless PMSM control technique is implemented, in which only two windings are excited at a time and third phase is used to measure back EMF for Rotor position detection. The information helps in the generation of PWM signals. This solution was transferred and used by Sharp - Japan for their refrigerator compressor control. In the year 1999 Sharp produced 140,000 refrigerators. Presently over 0.5 Million refrigerators are sold in Japanese market. This new technology developed by SKD is protected by US Patent 5,635,810.

Salient Features

	Optimized for motor control application
	CFC Free Refrigerator
	High Efficiency (>90% for motor + drive)
	Energy saving

BLDC MOTORS and CONTROLS

The Bldc motors are motors without the carbon brushes thereby decreasing the losses, maintenance and EMI etc. The Stator is 3 Phase wound and Rotor is made of Permanent magnets, therefore the brushes are eliminated. Three sensors are used for Rotor Position Estimator, which maintains the control over acceleration, Velocity and Position. These motors are commonly used in high efficiency and high-speed applications as prime mover. Another important application area is Servo Control.

These Motors and Controls are high performance. Main reason is the number of poles and high frequency operation. SKD is working on 800 to 1000 Hz electrical frequency, which theoretically should give 2 times better performance compare to other Industrial Servo Motors. Presently these motors are tested up to 1000 Hz electrical frequency at reduced load, and up to 400 Hz for full load. Further tests and qualification process are continued.

The steel for stator is CRNGO grade M18, 0.2 mm thick stampings and Magnets are NdFeB. To solve the problem of heat transfer (Thermal resistance), these motors are partially filled with oil. The main advantage of oil filling is to reduce the thermal resistance and to cool rotor magnets also. The losses on a typical motor are approx. 80 watt extra due to oil friction, still the oil helps in heat transfer and peak current rating.

Range of Motors (under development)

SIZE CODE

DIMENSIONS Mm

# POLES

TORQUE Nm

SPEED (RPM)

MAX PWR (W)

Estimated Weight kg

S11

28 X 28 X 70

4

0.05

30 K

50

0.4

S15 X

42 X 42 X 80

6

0.15

20 K

150

0.6

S22

56 X 56 X 90

6

0.3

20 K

400

1.2

S33

84 X 84 X 110

12

2.5

10 K

2.0 K

3.5

S44 A

112 X 112 X 140

12

7.5

10 K

7.5 K

6.5

S44 B

112 X 112 X 140

24

15

5 K

7.5 K

6.5

S55 A

140 X 140 X 130

16

15

6.6 K

9.0 K

7.5

S55 B

140 X 140 X 130

32

30

3.3 K

9.0 K

7.5

O_Rotor A

72 f x 68

24

7.5

5 K

3.0 K

4.0

TWIN ROTOR COAXIAL

225 X 225 X 150

180

125 CW + 125 CCW

666

8 K + 8 K

22.0

The rotor speed is also calculated from a single sensor information, which is used to generate V/F slope and to control the speed by Modulation Index. This solution has many advantages such as DSP handles sensors misalignment to some extent and provides phase advance at high speed.

Controls / Drives

BLDC motor is similar to PMSM with three Opto-sensor or Hall effect sensors used for position feedback. Therefore, its control is considered easier compared to PMSM. However, its performance can be significantly improved using DSP. The adjacent Figure shows the block diagram for controlling of BLDC motor. The DSP gets sensor status and process this information into electrical angle of rotor. Based on this information, the PWM signals are generated.

Common Features of Control

All motor solutions are built with Bus voltage compensation, over-current control and minimum protections of under-voltage, over-voltage and overload and also RS 232 interface for PC/ HOST communication for monitoring and control. The Master / Slave communication is under implementation in the Flying Car project which enables control of maximum 62 drives from a single serial port.

Electronic Controller

The complete range of SKD Advanced Motors are controlled by DSP based Electronic Controllers. All the controllers use PWM based technology for providing high efficiency. V/F Control provides Low Starting Current & Constant Torque which saves considerable Power in actual use.

Typical Applications

	Electric Vehicles
	Wind Mills
	Exhaust Fans
	Door Closers
	Domestic Appliances
	Automation
	Robotics and
	CNC Drives etc.