Mitsubishi Electric MELSERVO-J5 HK Series User Manual page 16

Sound generation
The brake lining may rattle during a low-speed operation; however, it poses no functional problem.
The noise may be reduced or eliminated by the machine resonance suppression filter set with the servo parameters. For
details, refer to "Machine resonance suppression filter" in the following manual.
MR-J5 User's Manual (Adjustment)
Selection of surge absorbers for electromagnetic brake circuit
The following shows an example of how to select a varistor as a surge absorber.
■Selection condition
Item
Electromagnetic brake specification
Desired suppression voltage
Durable surge application time
Relay
24 V DC
U
■Tentative selection and verification of surge absorber
• Maximum permissible circuit voltage of varistor
Tentatively select a varistor whose maximum permissible voltage is larger than Vb [V].
• Brake current (Ib)
Vb
Ib = [A]
R
• Energy (E) generated by brake coil
2
L × Ib
E = [J]
2
• Varistor limit voltage (Vi)
From the energy (E) generated in the brake coil and the varistor characteristic diagram, calculate the varistor limit voltage (Vi)
when the brake current (Ib) flows into the tentatively selected varistor during opening of the circuit.
Vi is favorable when the varistor limit voltage (Vi) [V] is smaller than the desired suppressed voltage (Vs) [V].
If Vi is not smaller than Vs, reselect a varistor or improve the withstand voltage of devices.
• Surge current width (τ)
Given that the varistor absorbs all energies, the surge current width (τ) is as follows.
E
τ = [S]
Vi × Ib
• Examining surge life of varistor
From the varistor characteristic diagram, find the guaranteed current value (Ip) in which the number of the surge application
life is N at the surge current width (τ). Calculate the guaranteed current value (Ip) ratio (Ip/Ib) to brake current (Ib).
If a sufficient margin is ensured for Ip/Ib, the number of the surge application life N [time] can be considered as favorable.
Other precautions
A leakage magnetic flux occurs at the shaft end of the servo motor with an electromagnetic brake. Note that chips, screws,
and other debris are attracted.
1 INTRODUCTION
14
1.5 Electromagnetic brake
Varistor Brake coil
Condition
R [Ω]: Resistance
L [H]: Inductance
Vb [V]: Power supply voltage
Vs [V] or less
N times