Braking Controls - BENSHAW RediStart EXEXMVRMX3 Series User Manual

7.5

Braking Controls

Overview
Maximum Load Inertia
HP
75
100
125
150
200
250
300
350
400
450
500
600
700
800
When the Stop Mode parameter is set to DC Brake, the MX
friction braking of a three-phase motor. The MX
to induce a stationary magnetic field that then exerts a braking torque on the motor's rotating rotor. The
braking current level and braking time required depends on the motor characteristics, the load inertia, and the
friction in the system.
3
The MX starter supports two different levels of DC injection braking:
1. Standard Duty Brake - For less than 6 x motor inertia.
2. Heavy Duty Brake - For NEMA specified inertia and two motor current feedback methods:
a) Standard Current Transformers (CTs)
b) Optional Hall Effect Current Sensor (LEM)
The optional Hall Effect Current sensor can be used when a more precise measurement of braking current is
necessary. This can occur if the DC injection braking is applied when the source supply has a very high short
circuit capability (very stiff) or in special instances when more precise braking current control is required.
The appropriate brake type and feedback method is preset from the factory. Please consult Benshaw for more
information if changes need to be made.
The following table shows maximum load inertia, NEMA MG1 parts 12 and 20. It is recommended a
thermistor or RTD be installed to protect the motor from overheating.
3600 1800
71 338
92 441
113 542
133 640
172 831
210 1017
246 1197
281 1373
315 1546
349 1714
381 1880
443 2202
503 2514
560 2815
7 - THEORY OF OPERATION
3
starter provides DC injection braking for fast and
3
starter applies a controlled DC current to the motor in order
Speed - RPM
1200 900
Inertia (lb-ft2)
904 1814
1181 2372
1452 2919
1719 3456
2238 4508
2744 5540
3239 6540
3723 7530
4199 8500
4666 9460
5130 -
6030 -
- -
- -
Braking Controls
720 600
3111 4831
4070 6320
5010 7790
5940 9230
7750 12060
9530 14830
11270 -
- -
- -
- -
- -
- -
- -
- -
514
7010
9180
11310
-
-
-
-
-
-
-
-
-
-
-
133